POT 2 Click
PID: MIKROE‐3325
Weight: 24 g
POT 2 click is a Click board™ with the accurate selectable reference voltage
output. By utilizing a multi-turn precision potentiometer, this Click board™
can provide very accurate voltage output on the AN pin of the mikroBUS™.
POT 2 click is also equipped with the SMD jumper, which allows the
maximum reference voltage to be selected between two typically used
values: 2.048V or 4.096V. Using a rail-to-rail buffering operational amplifier
which provides constant input and output impedance, this Click board™ is an
ideal solution when accurately controlled voltage reference is required.
POT 2 click is supported by a mikroSDK compliant library, which includes
functions that simplify software development. This Click board™ comes as a
fully tested product, ready to be used on a system equipped with the
mikroBUS™ socket.
Having the ability to adjust the voltage on the AN pin very accurately, this
Click board™ can be used for development of applications that require
voltage reference other than what is commonly available as an output from
a dedicated IC. This includes HMI applications where the potentiometer can
be used to provide fine control the movement of a step motor, or intensity of
a LED segment, backlight amount of a TFT screen, and similar applications
that require fine control of the voltage reference.
How does it work?
This Click board™ uses a very simple design: the MCP1541, a precision
voltage reference IC from Microchip is used to provide the voltage of 4.096V.
is fed to an input of an operational amplifier, that acts as the buffer, with the
unity gain. The output of the first buffer is fed to one end of a high-precision
trimmer-potentiometer. The second end of the potentiometer is grounded,
while the middle tap of the potentiometer is used as the input to a second
buffer. The output of the second buffer is routed to the AN pin of the
mikroBUS™, allowing the host microcontroller (MCU) to use the output
voltage for any purpose.
The design uses the MCP6022, a dual, rail-to-rail operational amplifier from
Microchip. This operational amplifier is a perfect choice for this design, as it
allows rail-to-rail operation, uses a single power supply of 5V, and has a
stable unity gain. Without the buffers, the variable impedance would affect
the reference voltage. The reference voltage IC can provide less than 10 mA,
with the significant voltage drop for output currents exceeding 2 mA.
Therefore, the MCP6022 used as a dual buffer ensures good stability of the
circuit.
The potentiometer itself is a multi-turn type of potentiometer which provides
high accuracy. It is equipped with a screw, which can be rotated 20 times
between the end positions. This allows the resistance to be precisely
selected. The fact that the screw fits tightly into the casing of the
potentiometer, ensures that no resistance variations are possible, unlike the
conventional knob or slider potentiometers.
POT 2 click is equipped with the SMD jumper, which is used to select the
voltage reference for the potentiometer. There are two options available:
2.048V and 4.096V. These values are the most commonly used voltage
references for different kinds of A/D converters. Most MCUs which use 3.3V
for the power supply, do not have the option to use 4.096V (full voltage
output of the MCP1541 IC), so an option to select 2.048V by dividing the
output voltage of the MCP1541 IC, is very useful in that case. The voltage
reference can be selected by moving the SMD jumper labeled as VRef SEL to
the desired position (2.048V or 4.096V).
Specifications
Type
Measurements
Applications
It can be used for development of different types of HMI
applications where the potentiometer can be used to
provide fine control the movement or to change the
intensity of a LED segment in fine steps, backlight
amount of a TFT screen, etc.
On-board
modules
MCP1541, a precision voltage reference IC; MCP6022, a
dual, rail-to-rail operational amplifier, both from
Microchip
Key Features
High precision, 20 turns trimmer potentiometer, buffered
reference voltage output, selectable maximum value for
the adjustable voltage reference
Interface
Analog
Input
Voltage
5V
Click board
size
M (42.9 x 25.4 mm)
Pinout diagram
This table shows how the pinout on POT 2 Click corresponds to the pinout on
the mikroBUS™ socket (the latter shown in the two middle columns).
Notes
Pin
Ref. Voltage OUT
AC
1
AN
PWM
16
NC
NC
2
RST
INT
15
NC
NC
3
CS
RX
14
NC
NC
4
SCK
TX
13
NC
NC
5
MISO
SCL
12
NC
NC
6
MOSI
SDA
11
NC
NC
7
3.3V
5V
10
+5V
Power Supply
GND
8
GND
GND
9
GND
Ground
Ground
Pin
Notes
Onboard settings and indicators
Label
Name
Default
LD1
PWR
-
JP1
VRef SEL
Left
Description
Power LED indicator
Reference voltage level selection: left
position 2.048V, right position 4.096V
Software support
We provide a library for the POT 2 Click on our LibStock page, as well as a
demo application (example), developed using MikroElektronika compilers. The
demo can run on all the main MikroElektronika development boards.
Library Description
The library contains the functions needed to start and read the ADC values.
Key functions:
void pot2_adcInit() - ADC Init function.
void pot2_adcSetInputChannel() - ADC set input channel function.
uint32_t pot2_adcRead() - ADC read function.
Examples description
The application is composed of the three sections :
System Initialization - Initializes LOG to print data that is read from ADC.
Application Initialization - Initialization ADC Init and sets ADC input channel.
Application Task - (code snippet) - Reads data from ADC and logs data to USBUART every 500
ms.
void applicationTask()
{
uint16_t ADC_value;
char demoText[ 50 ];
ADC_value = pot2_adcRead();
WordToHex(ADC_value, demoText);
mikrobus_logWrite(" ADC value: 0x", _LOG_TEXT);
mikrobus_logWrite(demoText, _LOG_LINE);
Delay_ms( 500 );
}
The full application code, and ready to use projects can be found on
our LibStock page.
Other mikroE Libraries used in the example:
ADC
Additional notes and informations
Depending on the development board you are using, you may need USB UART
click, USB UART 2 click or RS232 click to connect to your PC, for development
systems with no UART to USB interface available on the board. The terminal
available in all MikroElektronika compilers, or any other terminal application
of your choice, can be used to read the message.
https://www.mikroe.com/pot‐2‐click/2‐13‐19
