AN3301
Application note
S-Touch® STMPE812A: a hardware and software guide
Introduction
The STMPE812A is a 4-wire resistive touchscreen controller with an integrated 4-bit port
expander. The touchscreen controller is designed to be fully autonomous, requiring only
minimal CPU intervention for sampling, filtering and preprocessing operations.
The purpose of this document is to highlight the guidelines and information complementary
to the datasheet that is necessary for a proper operation of the STMPE812A device in
applications.
The first part of the document highlights information on the hardware. This includes external
components/connectivity, power, PCB design and etc.
The second part of the document focuses on information in software in which programming
reference codes are shown. This part is to be used in conjunction with the STMPE812A
software library available in www.st.com.
December 2010
Doc ID 18161 Rev 1
1/35
www.st.com
Contents
AN3301
Contents
1
Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1
Typical application circuit and external components . . . . . . . . . . . . . . . . . 5
1.2
Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.1
1.3
Power modes transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4
Touchscreen tracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.1
2
2/35
Track resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.5
Noise prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.6
Noise filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.7
PWM controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.8
ADC controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.9
GPIO output configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.9.1
Push-pull . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.9.2
Open drain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1
3
Power sequence (fail safe) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Touchscreen controller acquisition modes . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.1
Data acquisition by internal timer (ACQ_mode “00”) . . . . . . . . . . . . . . . 13
2.1.2
Data acquisition by ACQ command (ACQ_mode “01”) . . . . . . . . . . . . . 14
2.1.3
Data acquisition by host read control (ACQ_mode “10”) . . . . . . . . . . . . 14
2.2
Embedded data valid bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.3
Pen down interrupt mode
2.4
TSC_DATA read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.5
Touchscreen controller sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.6
Programming guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.6.1
Touchscreen initialization and interrupt handling (pen down mode) . . . 19
2.6.2
Touchscreen initialization and interrupt handling (normal interrupt mode)
23
2.6.3
GPIO initialization and interrupt handling . . . . . . . . . . . . . . . . . . . . . . . 28
2.6.4
ADC initialization and interrupt handling . . . . . . . . . . . . . . . . . . . . . . . . 29
2.6.5
PWM initialization and interrupt handling . . . . . . . . . . . . . . . . . . . . . . . 32
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Doc ID 18161 Rev 1
AN3301
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Typical application schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Track resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Noise prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
PWM LED driving configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
GPIO push-pull configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
GPIO open drain configuration (output low) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
GPIO open drain configuration (output high) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Data acquisition by internal timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Data acquisition by ACQ command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Data acquisition by host read command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
TSC data register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Touchscreen controller sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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List of tables
AN3301
List of tables
Table 1.
Table 2.
Table 3.
4/35
Power modes vs. touchscreen/GPIO/Interrupt/PWM data . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Example of sampling time calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Doc ID 18161 Rev 1
AN3301
Hardware
1
Hardware
1.1
Typical application circuit and external components
Figure 1.
Typical application schematic
1 .65V – 3 .6 V
Y+
VCC
C1
STMPE812A
R1
RESETN
Y-
IN T (P 2 )
X-
R2
R3
S C LK
4-wire
resistive
touchscreen
X+
A D C inpu t
(P 1 )A D C
R4
R5
SDATA
(P 0 )A D D R
SDA
SCL
IN T
GND
RESET
AM004192V1
Note:
1
P0 pin is the I2C address bit upon power up or reset and is configurable to GPIO
2
P1 pin is configurable to GPIO/ADC/PWM (ADC Vin must be less than VCC)
3
P2 pin is configurable to GPIO/INT
4
Assuming GPIO controlling RESET input is of open drain type
In a typical application, the following external components are required:
●
R1: 2.2k-10kΩ pull up resistor at RESET
●
R2: 2.2k-10kΩ pull up resistor at INT.
●
R3: 2.2k-10kΩ pull up resistor at SCLK
●
R4: 2.2k-10kΩ pull up resistor at SDATA
●
R5: 2.2k-10kΩ pull up resistor at ADDR
●
C1: 100 nF capacitor at VCC
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Hardware
1.2
AN3301
Power supply
The implementation and layout of the power connection’s section is fundamental for the
correct operation of the STMPE812A touchscreen controller.
The STMPE812A device is equipped with a 12-bit ADC that is used during the touchscreen
controller and auxiliary voltage measurement operations.
The analog blocks require a clean and stable supply voltage in order to operate in optimum
performance. In the STMPE812, the analog blocks and the digital core are supplied by VCC.
The operating VCC voltage range is 1.65 V to 3.6 V. Power consumption will be increased
with the increase in VCC. The lowest power consumption is at VCC = 1.8 V.
It is a good practice to connect a 0.1µF filtering capacitor as close as possible to the VCC
pin.
1.2.1
Power sequence (fail safe)
All GPIOs and sense pins of STMPE812A are NOT fail safe. This means that it is necessary
to make sure that the VCC supply to STMPE812A is first turned before driving the GPIO
inputs.
All other pins (SCL and SDA) are with fail safe structure. It is possible to turn on the pull-up
supply before VCC.
6/35
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AN3301
1.3
Hardware
Power modes transition
The following table highlights the states of touchscreen FIFO, GPIO, Interrupt and PWM
during the various power modes:
–
Active mode
–
Hibernation mode
–
Reset
Table 1.
Power modes vs. touchscreen/GPIO/Interrupt/PWM data
Active mode
Hibernation mode
Reset (HW, SW, POR
and General call)
Touchscreen FIFO data
Active
Sustained
Cleared
GPIO configuration, pin
state and data
Active
Sustained
Cleared
Interrupt configuration
and data
Active
Sustained
Cleared
PWM configuration and
data
Active
Sustained
Cleared
Description
Hibernation mode is entered automatically when ALL of the following listed activities are
met:
●
Absent of I2C transaction with valid STMPE812A slave address for 10 ms
●
PWM disabled
●
ADC disabled
●
Absent of GPIO input transition for 10 ms
●
Absent of touchsceen or pen down interrupt for 10 ms
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Hardware
1.4
AN3301
Touchscreen tracks
The touchscreen tracks (X+, X-, Y+, Y-) are sensitive lines. Noise may be captured by the
touchscreen tracks if the line is too long and if placed nearby noisy lines, for example the
digital data lines and the I2C/SPI lines.
Although there is no recommended standard for track sizes, tracks that are too long reduce
the resolution of the touchscreen controller. As a matter of fact, long tracks introduce a
voltage drop during the measurement cycle at the terminal of the touchscreen panel.
1.4.1
Track resistance
Any track has a certain amount of resistance, thus reducing the effective resolution of the
touchscreen controller.
During the measurement, the current flows to the touchscreen panel through the tracks. If
the resistance is too high, the voltage in the panel terminal is no longer at the same level as
VIO and GND.
From Figure 2 it can be seen that, during the measurement cycle, the device bias the
touchscreen panel with the VIO voltage. Due to the track resistance, the voltage at panel's
terminals is:
Equation 1
Vx = V IO ⋅ R x ⁄ ( R1 + R2 + Rx )
Hence, the effective resolution is reduced by the same factor as well. The track resistance
may be reduced by designing the track as short as possible with a reasonable width.
Figure 2.
Track resistance
Track resistance, R1
VIO
Vx
Touch panel
resistance, Rx
Track resistance, R2
GND
AM004193V2
8/35
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AN3301
1.5
Hardware
Noise prevention
Noise may be coupled to the tracks connecting the touchscreen and this should be
prevented as much as possible.
Two practices may be applied:
1.
Prevent the tracks overlap with other noisy signal tracks, such as I2C/SPI lines and
digital data lines. If the overlap is not avoidable, GND lines separation between
touchscreen lines and noisy lines is recommended (in more than 2 layers PCB).
2.
Put GND shielding at each side of touchscreen tracks routing.
Figure 3.
Noise prevention
TSC
Noisy tracks
Bottom Layer
GND
Other
Noisy lines
GND
GND
TSC tracks
Top Layer
AM004194V2
1.6
Noise filtering
A filtering capacitor can be placed on the touchscreen tracks to further suppress the noise.
In this case, the best location for the filtering capacitor is as near as possible to the
STMPE812A sense pins (X+, X-, Y+, Y-).
The values recommended for the filtering capacitor are:
1. 1-2 nF for an LCD less than 6 inches
2. 5-10 nF for an LCD bigger than 6 inches
The Settling time and Touch detect delay registers must be set correctly to adapt to the
filtering capacitor, otherwise the touchscreen controller may not work properly. Additional
information is found in the STMPE812A datasheet.
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Hardware
1.7
AN3301
PWM controller
The STMPE812A is integrated with push-pull type of GPIO/PWM outputs. At VCC of 3.3 V,
the outputs are able to provide 8mA of sourcing (out of device) and 12mA of sinking (into
device) current capability. As such, STMPE812A is able to support LED driving in both
sourcing and sinking configuration.
Note: the PWM timing and duty cycle settings in datasheet are based on a LED sourcing
configuration. When used in sinking configuration, the inversion must be executed
accordingly.
Figure 4.
PWM LED driving configurations
C u rre n t s o u rc in g
co n fig u ra tio n (8 m A )
S T M P E 812 A
C u rre n t s in k in g
co n fig u ra tio n (1 2 m A )
S T M P E 812 A
P W M (A 1 )
VCC
P W M (A 1 )
AM004194V1
10/35
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AN3301
1.8
Hardware
ADC controller
The STMPE812A is equipped with a 12-bit analog-to-digital converter (ADC). Besides the
use for ADC conversion during touchsceen controller operation, it is possible to be used as
general purpose ADC conversion for up to maximum two external auxiliary analog signals
feed through pins B2 and C2.
The touchscreen controller has the priority for the ADC conversion. Selection of conversion
of the two external auxiliary analog signals is programmed through Bit[0] of the ADC control
register (0x20).
Whenever the touchscreen data acquisition is initiated, the ADC conversion is triggered
automatically without needs to program the ADC control register. Writing ‘1’ to Bit[6] of ADC
Control register to initialize conversion for Touchscreen data is redundant and will result in
higher current consumption if ADC is in continuous capture mode.
The STMPE812A is integrated with an internal charge pump in order to ensure ADC
performance in low VCC condition. The internal charge pump should be turned on through
ADC control register in the device initialization phase whenever the VCC is less than 2.5 V.
Important: If VCC is higher than 2.5 V, it is important to ensure the charge pump is
disabled to prevent possible reliability issue or permanent damage of the device.
1.9
GPIO output configurations
The STMPE812A provides push-pull type of GPIO output. If open drain GPIO outputs are
required, it is configurable, with a tweak to the software programming routine. See Figure 5,
Figure 6 and Figure 7.
1.9.1
Push-pull
Set the GPIO to output state through PORT_FUNTION (0x04) register. Input path will be
disabled. Output path will be enabled in push-pull configuration.
Figure 5.
GPIO push-pull configuration
STMPE812A
enabled
OUTPUT
GGPPIO
IOxx
INPUT
disabled
AM004195V1
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Hardware
1.9.2
AN3301
Open drain
GPIO output driven low by STMPE812A
Set the GPIO to output state through PORT_FUNTION (0x04) register. Input path is
disabled. Set the output state to LOW through GPIO_CLR_PIN (0x11) register. Output path
is enabled and pull GPIO pin LOW.
Figure 6.
GPIO open drain configuration (output low)
VCC
STMPE812A
enable
External
pull up
OUTPUT
G P IO x
GPIOx
INPUT
GPIO = LOW
disable
AM004197V1
GPIO output pulled high by external pull up resistor
Set the GPIO to input state through PORT_FUNTION (0x04) register. Input path is enabled
and output path disabled. GPIO will be pulled high by external pull up resistor.
Figure 7.
GPIO open drain configuration (output high)
VCC
STMPE812A
enable
External
pull up
OUTPUT
G P IO x
GPIOx
INPUT
GPIO = HIGH
disable
AM004198V1
12/35
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AN3301
Software
2
Software
2.1
Touchscreen controller acquisition modes
2.1.1
Data acquisition by internal timer (ACQ_mode “00”)
In this mode, the system configures STMPE812A to sample at a predefined rate (e.g. 10ms)
through TSC_Sampling_Rate register (0x43). On detecting a touch, it starts the sensing
sequence and on completion of sampling (thus data available for reading), it interrupts the
Host. If the Host does not access the data by the time the next data is available, the old data
is overwritten.
Programming sequence:
1.
Initialize touchscreen controller
2.
Initialize interrupt
3.
Wait for interrupt
4.
Upon interrupt, read ISR
5.
Upon touch data available, read touch data
Figure 8.
Data acquisition by internal timer
InInitialization
itializa tio n
TTouched
o u ch ed
NNo
o TTouch
ouch
SSampling
am p lin g
Agenda:
Sampling
S am p lin g
No Touch
Sampling
S am p lin g
STMPE812A sens interrupt to Host
Host read ISR
Host read touch data when available
AM004199V1
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Software
2.1.2
AN3301
Data acquisition by ACQ command (ACQ_mode “01”)
In this acquisition mode, the STMPE812A merely informs the system host on detecting a
touch. As and when sampling is desired, host issues an “ACQ” command that sets
STMPE812A into a complete sampling cycle. Host may read the data after a period of time,
or poll the interrupt status bit for data availability.
Programming sequence:
1.
Initialize touchscreen controller
2.
Initialize interrupt (Pen Down mode)
3.
Wait for interrupt
4.
Upon interrupt, issue ACQ command
5.
Poll ACQ bit for data available
6.
Upon touch data available, read touch data
Figure 9.
Data acquisition by ACQ command
InInitialization
itializa tio n
TTouched
o u ch ed
NNo
o TTouch
ouch
SSampling
am p lin g
Agenda:
Sampling
S am p lin g
No Touch
Sampling
S am p lin g
STMPE812A sens touched interrupt to Host
Host issues ACQ command
Host polls ACQ bit or ISR for sampling completion
Host read touch data when available
AM004200V1
2.1.3
Data acquisition by host read control (ACQ_mode “10”)
The data acquisition by the host read control is the most bandwidth efficient method for
touchscreen interfaces. For 100 Hz sampling with 12-bit X, 12-bit Y, 8-bit Z, only one I2C
transaction (5 bytes data read) is required for every 10 ms. Inclusive of overheads, this
translates to approximately 100 bit time.
At 400 kHz I2C speed, this is just 2.5% of total bandwidth.
A new sample is taken every time the host reads the previously sampled data. If host reads
the data late, the device simply stays longer in hibernation.
Note:
14/35
It is necessary to counter check with the data valid bit for each data read.
Doc ID 18161 Rev 1
AN3301
Software
Programming sequence:
1.
Initialize touchscreen controller
2.
Initialize interrupt (pen down mode)
3.
Wait for interrupt
4.
Upon interrupt, issue data read (counter check with the embedded data valid bit for the
validity of the corresponding data)
5.
Start host timer (typical 10ms depends on the programmed sampling time)
6.
Upon time out, issue data read (counter check with the embedded data valid bit for the
validity of the corresponding data)
Figure 10. Data acquisition by host read command
Initialization
Touched
No Touch
Sampling
Agenda:
Sampling
No Touch
Sampling
STMPE812 sends touched interrupt to Host
Host read touch data
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Software
2.2
AN3301
Embedded data valid bit
In order to facilitate a more bandwidth efficient for data read, it is possible to program
through Bit[5] of TSC_DET_CFG2 register (0x42) whereby the data valid bit is embedded in
within the first byte of the touch data (FIFO).
Figure 11. TSC data register
B it[4]
O pM ode
B it[5]
S tatusR ead
N um ber of
b ytes to
read from
T S C _D ata
0
0
4
[11:4] of X
[3:0] of X
[11:8] of Y
[7:0] of Y
[7:0] of Z
-
1
0
3
[11:4] of X
[3:0] of X
[11:8] of Y
[7:0] of Y
-
-
0
1
5
D ata valid
status
[11:4] of X
[3:0] of X
[11:8] of Y
[7:0] of Y
[7:0] of Z
1
1
4
D ata valid
status
[11:4] of X
[3:0] of X
[11:8] of Y
[7:0] of Y
-
T S C _D E T _C F G 2 R egister
B yte0
B yte1
B yte2
B yte3
B yte4
RSVD
7
6
5
4
3
2
V A LID
RSVD
1
0
AM08680V1
In applications whereby no GPIO input/PWM/ADC is used and Pen Down interrupt mode is
selected, it is no longer necessary to read the ISR register. The data valid info can be
obtained through the embedded data valid bit and the touch release info can be obtained
merely by observing the INT pin signal. (ie. INT low: touched; INT high: release).
2.3
Pen down interrupt mode
In Pen down interrupt mode, the INT pin signal is an OR function of the Pen Down and other
enabled GPIO/PWM/ADC interrupts at Port 0 to Port 3.
It is recommended to use Pen Down mode when the GPIO/PWM/ADC functions are not
required or the GPIO/PWM/ADC interrupts are not enabled. In this condition, the INT signal
provides the exclusive indication for touched (INT low) and release (INT high).
16/35
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AN3301
2.4
Software
TSC_DATA read
The TSC_DATA contains the converted data for touchscreen controller. Three to five bytes
readings are required depending on the programmed value in TSC_DET_CFG2 register.
In order to preserve the integrity of the data, it is mandatory to ensure the following:
System host to read exactly the number of bytes according to the programmed
operating mode
–
I2C host to insert a STOP condition after each data read command
Touchscreen controller sampling
The touchscreen controller sampling time is determined by the following programmable
parameters:
–
Touch detect delay
–
Settling time
–
ADC conversion time
–
MAV (median average filter)
–
TSC operating mode (X/Y or X/Y/Z acquisition)
Figure 12 illustrates the diagram of a complete sampling cycle. MAV is acting within the
Sampling period of X, Y and Z respectively.
Touch Detect Delay
Sampling Z
Settling Time
Sampling Y
Settling Time
Sampling X
Settling Time
Figure 12. Touchscreen controller sampling
Touch Detect Delay
2.5
–
A complete sampling cycle
AM08681V2
The overall sampling time/frequency can be calculated with below formulae.
Sampling time in X/Y/Z mode = touch detect delay *2 + (settling time + (ADC conversion
time * MAV)) * 3
Time taken for sampling in X/Y/Z mode = touch detect delay *2 + (settling time + (ADC
conversion time * MAV)) * 2
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Software
AN3301
Table 2.
Example of sampling time calculation
ADC
conversion time
50 µs
50 µs
50 µs
18/35
Touch detect
delay
40 µs
Settling time
40 µs
40 µs
40 µs
640 µs
640 µs
Doc ID 18161 Rev 1
MAV
Sampling
time/freq
(complete X/Y/Z
sample sets)
None
40*2 +
3*(40+(50*1))
=350 µs (2.8 K
sample sets/sec)
10-2
40*2 + 3*(40+
(50*10))
=1700 µs (588
sample sets/sec)
20-4
640*2 + 3*(640+
(50*20))
=6200 µs (161
sample sets/sec)
AN3301
2.6
Software
Programming guide
In this section, the reference software programming code is shared based on the general
application of the STMPE812A. This includes the initialization and interrupt handling
routines for touchscreen controller (in all 3 acquisition modes and both normal and pen
down interrupt modes), GPIO, ADC and PWM.
The reference code is supplemented by the STMPE812A software library.
2.6.1
Touchscreen initialization and interrupt handling (pen down mode)
The following is an example for touchscreen initialization, interrupt servicing routine in pen
down mode, whereby all other interrupt sources (eg. GPIO, PWM and ADC) are not used in
the application.
A: Initialization
void STMPE812A_Initialization (void) {
/*Enabling the Soft Reset in the System Control Register (0x03)*/
STMPE812A_SoftReset ();
/*Enabling the ADC and TSC Clocks in the System Control Register (0x03)*/
STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_ADC_CLK|STMPE812A_TSC_CLK);
/*Setting the Port - 2 as a special function in the Port Function Control Register
(0x04)*/
STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);
/*Setting the MAV_MODE [2:0] as ‘20 remove 4’, Precharge [1:0] as ‘no pre-charge’ and
Current _Limit [1:0] as ‘20mA’ in the TSC Control Register (0x40) respectively*/
STMPE812A_SetTSCController (STMPE812A_TSC_MAV_20_4, STMPE812A_TSC_NO_PRE,
STMPE812A_TSC_Current20M);
/*Setting the PenStrength [1:0] as ‘Most Sensitive (20K Pull-Up)’, TDetDly [2:0] as
‘40us’ and Settling [2:0] as ‘40us’ in the TSC Detection Configuration 1 Register
(0x41) respectively*/
STMPE812A_ConfigureTSC (STMPE812A_TSC_MOST_SEN, STMPE812A_TSC_TDD40,
STMPE812A_TSC_PDST40);
/*Setting the TSC operating mode OpMode [4] as ’12-bit X, 12-bit Y, 8-bit Z
acquisition’ in the TSC Detection Configuration 2 Register (0x42)*/
STMPE812A_SetTSCOpMode (STMPE812A_DISABLE);
/*Enabling the StatusRead [5] in the TSC Detection Configuration 2 Register (0x42)*/
STMPE812A_SetTSCStatusRead (STMPE812A_ENABLE);
/*Setting the Acq_Mode [7:6] as ‘Data acquisition timed by internal timer’ in the TSC
Detection Configuration 2 Register (0x42)*/
STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_INTERNAL_TIMER);
/*Setting the Acq_Mode [7:6] as ‘Data acquisition triggered by a write to “ACQ” bit’
in the TSC Detection Configuration 2 Register (0x42)*/
//STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_TRI_ACQ);
/*Setting the Acq_Mode [7:6] as ‘Data acquisition using Host-Controlled Sampling Rate
Control’ in the TSC Detection Configuration 2 Register (0x42)*/
//STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_HC_SRC);
/*Setting the TSC sampling rate value of ‘0x0A’ in the TSC Sampling Rate Register
(0x43)*/
STMPE812A_SetTSCSamplingRate (0x0A);
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/*Setting the INT_Mode [7] as ‘Pendown Interrupt Mode’ in the Interrupt Control
Register (0x08)*/
STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_PEN_DOWN);
/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/
STMPE812A_EnableGlobalInterrupt (TRUE);
/*Enabling the interrupt from the system related source of TSC_TOUCH and TSC_DATA to
the host in the Interrupt Enable Register (0x09)*/
STMPE812A_EnableInterrupt (STMPE812A_INT_TSC_TOUCH|STMPE812A_INT_TSC_DATA, TRUE);
/*Enabling the TSC operation in the System Control Register (0x03)*/
STMPE812A_EnableTouchscreen (TRUE);}
B: Interrupt handling (pen down mode)
Data acquisition timed by internal timer
void IRQHandler (void) {
u8 data [5];
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
/*Checking the Interrupt Pin Status goes low*/
if ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)
{
/*Start host timer with an interval of 13ms*/
/*Check below for the timer routine*/
TIM_Cmd (TIM2, ENABLE);
}
}
}
Data acquisition triggered by a write to “ACQ” bit
void IRQHandler (void) {
u8 data [5];
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
/*Checking the Interrupt Pin Status goes low*/
if ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)
{
/*Start host timer with an interval of 0ms*/
/*Check below for the timer routine*/
TIM_Cmd (TIM2, ENABLE);
}
}
}
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Data acquisition using host-controlled sampling rate control
void IRQHandler (void) {
u8 data [5];
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
/*Checking the Interrupt Pin Status goes low*/
if ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)
{
/*Reading the Interrupt status register and Dummy data of 4 bytes of x, y & z data
from the register address of 0x44 to 0x48*/
I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 5, &data [0]);
/*Start host timer with an interval of 13ms*/
/*Check below for the timer routine*/
TIM_Cmd (TIM2, ENABLE);
}
}
}
Micro-controller timer routine
Data acquisition timed by internal timer or data acquisition using host-controlled sampling
rate control:
void TIM2_IRQHandler (void) {
if (TIM_GetITStatus (TIM2, TIM_IT_CC1) != RESET)
{
/*Clearing the Timer 2 Interrupt pending bit from the Micro-controller*/
TIM_ClearITPendingBit (TIM2, TIM_IT_CC1);
/*Reading the Interrupt status register and 4 bytes of x, y & z data from the
register address of 0x44 to 0x48*/
I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 5, &Touch_Data [0]);
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/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data
[1] to Touch_Data [4] i.e. 4 bytes of x, y
& z data coordinates) in the main while
loop*/
Is_Pen_Down = TRUE;
/*Handling Coordinates codes should be here */
/*Checking either the bit 0 or 1 or both (touch bit [or] data bit [or] touch and
data bits) value from Interrupt status register goes high*/
if ((Touch_Data [0] & 0x03) > 0)
{
/*Getting the Captured value from the Micro-controller Timer2 CNT register*/
Capture = TIM2->CNT;
/*Setting the (Captured value+CCR1_VAL) to the Micro-controller Timer2
CCR1 register.*/
TIM_SetCompare1 (TIM2, capture + CCR1_Val);
/*Enabling the Micro-controller Timer2 for 13ms*/
TIM_Cmd (TIM2, ENABLE);
}
else
{
/*Disabling the Micro-controller Timer2*/
TIM_Cmd (TIM2, DISABLE);
/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data
coordinates) in the main while loop*/
Is_Pen_Down = FALSE;
}
}}
Data acquisition triggered by a write to “ACQ” bit
void TIM2_IRQHandler (void) {
if (TIM_GetITStatus (TIM2, TIM_IT_CC1) != RESET)
{
/*Clearing the Timer 2 Interrupt pending bit from the Micro-controller*/
TIM_ClearITPendingBit (TIM2, TIM_IT_CC1);
/* Sets the ACQ [4] in the TSC Control Register (0x40) */
STMPE812A_InitiateAcquisition ();
/* Waiting until the ACQ [4] in the TSC Control Register (0x40) goes low */
while (!STMPE812A_IsAcquisitionComplete ())
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{}
/*Reading the Interrupt status register and 4 bytes of x, y & z data from the
register address of 0x44 to 0x48*/
I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 5, &Touch_Data [0]);
/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data
[1] to Touch_Data [4] i.e. 4 bytes of x, y
& z data coordinates)*/
Is_Pen_Down = TRUE;
/*Handling Coordinates codes should be here */
/*Checking either the bit 0 or 1 or both (touch bit [or] data bit [or] touch and
data bits) value from Interrupt status register goes high*/
if ((Touch_Data [0] & 0x03) > 0)
{
/*Getting the Captured value from the Micro-controller Timer2 CNT register*/
Capture = TIM2->CNT;
/*Setting the (Captured value+CCR1_VAL) to the Micro-controller Timer2
CCR1 register.*/
TIM_SetCompare1 (TIM2, capture + CCR1_Val);
/*Enabling the Micro-controller Timer2 for 0ms*/
TIM_Cmd (TIM2, ENABLE);
}
else
{
/*Disabling the Micro-controller Timer2*/
TIM_Cmd (TIM2, DISABLE);
/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data
coordinates) in the main while loop*/
Is_Pen_Down = FALSE;
}
}}
2.6.2
Touchscreen initialization and interrupt handling (normal interrupt
mode)
The following is an example for device initialization, interrupt servicing routine in normal
interrupt mode.
A: Initialization
void STMPE812A_Initialization (void) {
/*Enabling the Soft Reset in the System Control Register (0x03)*/
STMPE812A_SoftReset ();
/*Enabling the ADC and TSC Clocks in the System Control Register (0x03)*/
STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_ADC_CLK|STMPE812A_TSC_CLK);
/*Setting the Port - 2 as a special function in the Port Function Control Register
(0x04)*/
STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);
/*Setting the MAV_MODE [2:0] as ‘20 remove 4’, Precharge [1:0] as ‘no pre-charge’ and
Current _Limit [1:0] as ‘20mA’ in the TSC Control Register (0x40) respectively*/
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STMPE812A_SetTSCController (STMPE812A_TSC_MAV_20_4, STMPE812A_TSC_NO_PRE,
STMPE812A_TSC_Current20M);
/*Setting the PenStrength [1:0] as ‘Most Sensitive (20K Pull-Up)’, TDetDly [2:0] as
‘40us’ and Settling [2:0] as ‘40us’ in the TSC Detection Configuration 1 Register
(0x41) respectively*/
STMPE812A_ConfigureTSC (STMPE812A_TSC_MOST_SEN, STMPE812A_TSC_TDD40,
STMPE812A_TSC_PDST40);
/*Setting the TSC operating mode OpMode [4] as ’12-bit X, 12-bit Y, 8-bit Z
acquisition’ in the TSC Detection Configuration 2 Register (0x42)*/
STMPE812A_SetTSCOpMode (STMPE812A_DISABLE);
/*Disabling the StatusRead [5] in the TSC Detection Configuration 2 Register (0x42)*/
STMPE812A_SetTSCStatusRead (STMPE812A_DISABLE);
/*Setting the Acq_Mode [7:6] as ‘Data acquisition timed by internal timer’ in the TSC
Detection Configuration 2 Register (0x42)*/
STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_INTERNAL_TIMER);
/*Setting the Acq_Mode [7:6] as ‘Data acquisition triggered by a write to “ACQ” bit’
in the TSC Detection Configuration 2 Register (0x42)*/
//STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_TRI_ACQ);
/*Setting the Acq_Mode [7:6] as ‘Data acquisition using Host-Controlled Sampling Rate
Control’ in the TSC Detection Configuration 2 Register (0x42)*/
//STMPE812A_SetTSCAcquisitionMode (STMPE812A_TSC_HC_SRC);
/*Setting the TSC sampling rate value of ‘0x0A’ in the TSC Sampling Rate Register
(0x43)*/
STMPE812A_SetTSCSamplingRate (0x0A);
/*Setting the INT_Mode [7] as ‘Normal Interrupt Mode’ in the Interrupt Control
Register (0x08)*/
STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_NORMAL);
/*Setting the INT_Type [1] as ‘Edge Interrupt Type’ in the Interrupt Control Register
(0x08)*/
STMPE812A_SetInterruptType (STMPE812A_INT_TYPE_EDGE);
/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/
STMPE812A_EnableGlobalInterrupt (TRUE);
/*Enabling the interrupt from the system related source of TSC_DATA and TSC_RELEASE
to the host in the Interrupt Enable Register (0x09)*/
/*For Acq_Mode [7:6] in the TSC Detection Configuration 2 Register (0x42) is set as
‘Data acquisition timed by internal timer’*/
STMPE812A_EnableInterrupt (STMPE812A_INT_TSC_DATA|STMPE812A_INT_TSC_REL, TRUE);
/*Enabling the interrupt from the system related source of TSC_TOUCH, TSC_DATA and
TSC_RELEASE to the host in the Interrupt Enable Register (0x09)*/
/*For Acq_Mode [7:6] in the TSC Detection Configuration 2 Register (0x42) is set as
either ‘Data acquisition triggered by a write to “ACQ” bit’ (OR) ‘Data acquisition
using Host-Controlled Sampling Rate Control’*/
//STMPE812A_EnableInterrupt
(STMPE812A_INT_TSC_TOUCH|STMPE812A_INT_TSC_DATA|STMPE812A_INT_TSC_REL, TRUE);
/*Enabling the TSC operation in the System Control Register (0x03)*/
STMPE812A_EnableTouchscreen (TRUE);}
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B: Interrupt handling (normal interrupt mode)
Data acquisition timed by internal timer
void IRQHandler (void) {
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
/*Reading the Interrupt status register*/
STMPE812A_GetInterruptStatus (&Touch_Data [0]);
/*Reading the 4 bytes of x, y & z data from the register address of 0x44 to 0x47*/
I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 4, &Touch_Data [1]);
/*Checking the bit 6(release bit) value from Interrupt status register goes low*/
if ((Touch_Data [0] & 0x40) == 0x00)
{
/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data
[1] to Touch_Data [4] i.e. 4 bytes of x, y & z data coordinates) in the main while
loop*/
Is_Pen_Down = TRUE;
}
/*Handling Coordinates codes should be here */
}
/*Checking the bit 6(release bit) value from Interrupt status register goes
high*/
if ((Touch_Data [0] & 0x40) == 0x40)
{
/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data
coordinates) in the main while loop*/
Is_Pen_Down = FALSE;
}
}}
Data acquisition triggered by a write to “ACQ” bit
void IRQHandler (void) {
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
/*Reading the Interrupt status register*/
STMPE812A_GetInterruptStatus (&Touch_Data [0]);
/*Checking either the bit 0 or 1(touch bit or data bit) value from Interrupt status
register goes high*/
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if (((Touch_Data [0] & 0x01) == 0x01) || ((Touch_Data [0] & 0x02) == 0x02))
{
/*Reading the 4 bytes of x, y & z data from the register address of 0x44 to 0x47*/
I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 4, &Touch_Data [1]);
/* Sets the ACQ [4] in the TSC Control Register (0x40) */
STMPE812A_InitiateAcquisition ();
/* Waiting until the ACQ [4] in the TSC Control Register (0x40) goes low */
while (!STMPE812A_IsAcquisitionComplete ())
{}
}
/*Checking the bit 1(data bit) value from Interrupt status register goes high*/
if ((Touch_Data [0] & 0x02) == 0x02)
{
/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data
[1] to Touch_Data [4] i.e. 4 bytes of x, y & z data coordinates) */
Is_Pen_Down = TRUE;
/*Handling Coordinates codes should be here */
}
/*Checking the bit 6 (release bit) value from Interrupt status register goes high*/
if (((Touch_Data [0] & 0x40) == 0x40))
{
/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data
coordinates) in the main while loop*/
Is_Pen_Down = FALSE;
}
}}
Data acquisition using host-controlled sampling rate control
void IRQHandler (void) {
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
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/*Reading the Interrupt status register*/
STMPE812A_GetInterruptStatus (&Touch_Data [0]);
/*Checking either the bit 0 or 1(touch bit or data bit) value from Interrupt status
register goes high*/
if (((Touch_Data [0] & 0x01) == 0x01) || ((Touch_Data [0] & 0x02) == 0x02))
{
/*Reading the 4 bytes of x, y & z data from the register address of 0x44 to 0x47*/
I2C_Read_Data (STMPE812A_SLAVE_ADDR, STMPE812A_TSC_DATA, 4, &Touch_Data [1]);
}
/*Checking the bit 1(data bit) value from Interrupt status register goes high*/
if ((Touch_Data [0] & 0x02) == 0x02)
{
/*Sets the global variable (Is_Pen_Down) to handle the global variables (Touch_Data
[1] to Touch_Data [4] i.e. 4 bytes of x, y & z data coordinates) in the main while
loop*/
Is_Pen_Down = TRUE;
/*Handling Coordinates codes should be here */
}
/*Checking the bit 6 (release bit) value from Interrupt status register goes high*/
if (((Touch_Data [0] & 0x40) == 0x40))
{
/*Resets the global variable (Is_Pen_Down) to clear the point (x, y & z data
coordinates) in the main while loop*/
Is_Pen_Down = FALSE;
}
}}
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GPIO initialization and interrupt handling
The following is an example for GPIO initialization and interrupt servicing routine.
A: Initialization
void STMPE812A_GPIO_Initialization (void) {
/*Enabling the Soft Reset in the System Control Register (0x03)*/
STMPE812A_SoftReset ();
/*Enabling the GPIO Clock in the System Control Register (0x03)*/
STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_GPIO_CLK);
/*Setting the Port - 2 as a special function in the Port Function Control Register
(0x04)*/
STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);
/*Setting the Port - 1 as a GPIO Input in the Port Function Control Register (0x04)*/
STMPE812A_SetPortFunction (STMPE812A_PORT1, STMPE812A_PORT_FUNC_GPIO_IP);
/*Enabling the IO-1 [1] as GPIO Falling Edge Detection in the GPIO Falling Edge
Detection Register (0x14)*/
STMPE812A_EnableGPIOFallingEdgeInterrupt (STMPE812A_IO1, TRUE);
/*Setting the INT_Mode [7] as ‘Normal Interrupt Mode’ in the Interrupt Control
Register (0x08)*/
STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_NORMAL);
/*Setting the INT_Type [1] as ‘Level Interrupt Type’ in the Interrupt Control
Register (0x08)*/
STMPE812A_SetInterruptType (STMPE812A_INT_TYPE_LEVEL);
/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/
STMPE812A_EnableGlobalInterrupt (TRUE);
/*Enabling the interrupt from the system related source of P1 to the host in the
Interrupt Enable Register (0x09)*/
STMPE812A_EnableInterrupt (STMPE812A_INT_P1, TRUE);
}
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B: Interrupt handling
void IRQHandler (void) {
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
/*Checking the Interrupt Pin Status goes low*/
while ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)
{
/*Reading the Interrupt status register*/
STMPE812A_GetInterruptStatus (&Touch_Data [0]);
/*Checking the bit 3(P1 bit) value from Interrupt status register goes high*/
if ((Touch_Data [0] & 0x08) == 0x08)
{
/*Printing“GPIO Falling Edge is Detected” on the monitor screen*/
printf (“GPIO Falling Edge is Detected”);
}
}
}}
2.6.4
ADC initialization and interrupt handling
The following is an example for ADC initialization and interrupt servicing routine.
A: Initialization
void STMPE812A_ADC_Initialization (void) {
/*Enabling the Soft Reset in the System Control Register (0x03)*/
STMPE812A_SoftReset ();
/*Enabling the ADC and GPIO Clocks in the System Control Register (0x03)*/
STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_ADC_CLK|STMPE812A_GPIO_CLK);
/*Setting the Port - 2 as a special function in the Port Function Control Register
(0x04)*/
STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);
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/*Setting the Port - 1 as an ADC Input in the Port Function Control Register (0x04)*/
STMPE812A_SetPortFunction (STMPE812A_PORT1, STMPE812A_PORT_FUNC_ADC_IP);
/*Setting the ADC_MODE [7] as 'One-shot capture', ADC_FREQ [5:4] as '15Ksamples/sec'
and ADC_PORT
in the ADC Control Register (0x20) respectively*/
STMPE812A_SetADC (STMPE812A_ADC_1_SHOT_CAPTURE, STMPE812A_ADC_FREQ_15K,
STMPE812A_ADC_PORT);
/*Setting the INT_Mode [7] as ‘Normal Interrupt Mode’ in the Interrupt Control
Register (0x08)*/
STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_NORMAL);
/*Setting the INT_Type [1] as ‘Level Interrupt Type’ in the Interrupt Control
Register (0x08)*/
STMPE812A_SetInterruptType (STMPE812A_INT_TYPE_LEVEL);
/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/
STMPE812A_EnableGlobalInterrupt (TRUE);
/*Enabling the interrupt from the system related source of P1 to the host in the
Interrupt Enable Register (0x09)*/
STMPE812A_EnableInterrupt (STMPE812A_INT_P1, TRUE);
/*Starting the ADC Conversion (Initiate Data Acquisition by setting the bit [6]) in
the ADC Control Register (0x20)*/
STMPE812A_StartADC (TRUE);
}
Interrupt handling
void IRQHandler (void) {
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
/*Checking the Interrupt Pin Status goes low*/
while ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)
{
/*Reading the Interrupt status register*/
STMPE812A_GetInterruptStatus (&Touch_Data [0]);
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/*Checking the bit 3(P1 bit) value from Interrupt status register goes high*/
if ((Touch_Data [0] & 0x08) == 0x08)
{
/*Getting the12 bits ADC data from the ADC Data Register (0x21 & 0x22) */
STMPE812A_GetADCData (&adcdata);
/*Printing the received “adcdata” value on the monitor screen*/
printf ("%ld\n\r", adcdata);
/*Starting the ADC Conversion (Initiate Data Acquisition by setting the bit [6]) in
the ADC Control Register (0x20)*/
STMPE812A_StartADC (TRUE);
}
}
}}
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PWM initialization and interrupt handling
The following is an example for PWM initialization and interrupt servicing routine.
A: Initialization
void STMPE812A_PWM_Initialization (void) {
/*Enabling the Soft Reset in the System Control Register (0x03)*/
STMPE812A_SoftReset ();
/*Enabling the PWM and GPIO Clocks in the System Control Register (0x03)*/
STMPE812A_SetClock (STMPE812A_ENABLE, STMPE812A_PWM_CLK|STMPE812A_GPIO_CLK);
/*Setting the Port - 2 as a special function in the Port Function Control Register
(0x04)*/
STMPE812A_SetPortFunction (STMPE812A_PORT2, STMPE812A_PORT_FUNC_SPECIAL_FUNC);
/*Setting the Port - 1 as a special function in the Port Function Control Register
(0x04)*/
STMPE812A_SetPortFunction (STMPE812A_PORT1, STMPE812A_PORT_FUNC_SPECIAL_FUNC);
/*Setting the Burst_Length [1:0] as ‘8mS’ in the PWMClockDiv Register (0x50) */
STMPE812A_SetPWMBurstLengh (STMPE812A_PWM_BURSTLENGTH_8MS);
/*Setting the Div [4:0] value as ‘0’ in the PWMClockDiv Register (0x50)
respectively*/
STMPE812A_SetPWMClockDivider (0);
/*Setting the Brightness [7:4] as ‘Duty Cycle Ratio 8: 8 (50.00%)’, BurstMultiplier
[3:2] value as ‘1’ and Off_State [1] as ‘PWM Output “LOW” when PWM not running’ in
the PWMControl1 Register (0x51) respectively*/
STMPE812A_ConfigurePWM (STMPE812A_PWM_DUTY_CYCLE_50_00, 1,
STMPE812A_PWM_OFF_STATE_HIGH);
/*Setting the INT_Mode [7] as ‘Normal Interrupt Mode’ in the Interrupt Control
Register (0x08)*/
STMPE812A_SetInterruptMode(STMPE812A_INT_MODE_NORMAL);
/*Setting the INT_Type [1] as ‘Level Interrupt Type’ in the Interrupt Control
Register (0x08)*/
STMPE812A_SetInterruptType (STMPE812A_INT_TYPE_LEVEL);
/*Enabling the Global Interrupt in the Interrupt Control Register (0x08)*/
STMPE812A_EnableGlobalInterrupt (TRUE);
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/*Enabling the interrupt from the system related source of P1 to the host in the
Interrupt Enable Register (0x09)*/
STMPE812A_EnableInterrupt (STMPE812A_INT_P1, TRUE);
/*Enabling the PWM Controller Sequence in the PWMControl1 Register (0x51)*/
STMPE812A_EnablePWM (TRUE);
}
B: Interrupt handling
void IRQHandler (void) {
if (GetITStatus (INTERRUPT_LINE)! = RESET)
{
/*Clearing the Interrupt pending bit from the Micro-controller*/
ClearITPendingBit (INTERRUPT_LINE);
/*Checking the Interrupt Pin Status goes low*/
while ((GPIO_INTERRUPT->IDR & GPIO_PIN_INTERRUPT) == 0)
{
/*Reading the Interrupt status register*/
STMPE812A_GetInterruptStatus (&Touch_Data [0]);
/*Checking the bit 3(P1 bit) value from Interrupt status register goes high*/
if ((Touch_Data [0] & 0x08) == 0x08)
{
/*Enabling the PWM Controller Sequence in the PWMControl1 Register (0x51)*/
STMPE812A_EnablePWM (TRUE);
}
}
}}
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Revision history
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Revision history
Table 3.
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Document revision history
Date
Revision
14-Dec-2010
1
Changes
Initial release.
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