MIKROE-2396

Page 1 of 2 R Meter click From MikroElektonika Documentation R Meter click is a mikroBUS™ add-on board with circuitry for measuring the value of resistors. The board can be used to measure a wide range of resistors (from 0 to 1 Mega Ohm). It has three plates for SMD resistors (0603, 0805, 1206) and a header for thru hole resistors. R Meter click Features and usage notes The design of R Meter click is based on a non-inverting amplifier circuit, with the measured resistor placed in a feedback loop that influences the gain of the amplifier. The analog output is fed through a 12-bit ADC with the final output going through the mikroBUS™ SPI interface. Since the ADC has a limited minmax range (0-2043), R Meter click employs a multiplexer that can adjust the input signal to the amplifier and thus allow the same ADC to measure four different scopes of values (0-1k , 1k-100k, 100k-1M) Schematic also available in PDF (http://cdndocs.mikroe.com/images/3/39/R-meter-clickschematic.pdf) The supplied firmware (available on Libstock) automatically scans the ADC value and switches the multiplexer output based on the resistor in place. The multiplexer interfaces directly with the target board MCU through mikroBUS™ S1, S2, and S3 pins (in place of default mikroBUS™ PWM, INT and RST). Onboard screw terminals are placed to allow the click to be used with multimeter probes. R Meter click is a handy tool but it’s not to be used as a precision instrument. The linearity of the OpAmp impacts the measurement. R Meter click IC/Module 74HC4053 (http://www.nxp.com/documents/data_sheet/74HC_HCT4053.pdf) REF2925 (http://www.ti.com/general/docs/lit/getliterature.tsp? genericPartNumber=ref2925&fileType=pdf) AD8615 (http://www.analog.com/media/en/technicaldocumentation/data-sheets/AD8615_8616_8618.pdf) Interface SPI, S1, S2, S3 Power supply 5V Website www.mikroe.com/click®-meter (http://www.mikroe.com/click/r-meter) The board is designed to use a 5V power supply. Programming This example shows how to set up R Meter click, and read out the resistance in ohms (Ω) every 250 ms. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 #include #include "r_meter.h" //sbits sbit S1 at GPIOA_ODR.B0; sbit S2 at GPIOD_ODR.B10; sbit S3 at GPIOC_ODR.B2; sbit R_METER_CS at GPIOD_ODR.B13; //Prototypes void system_setup( void ); //Main void main() { //Local Declarations char txt[20] = { 0 }; float ohms_var = 0; //Setup system_setup(); while (1) { ohms_var = r_meter_get_ohms(); if( ohms_var == 0 ) UART1_Write_Text( "Over Range\r\n" ); else { FloatToStr( ohms_var, txt ); UART1_Write_Text( "OHMS: " ); UART1_Write_Text( txt ); UART1_Write_Text( "\r\n" ); } delay_ms(250); Page 2 of 2 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 } } void system_setup( void ) { // GPIOs GPIO_Digital_Output( &GPIOD_BASE, _GPIO_PINMASK_10 | _GPIO_PINMASK_13 ); GPIO_Digital_Output( &GPIOC_BASE, _GPIO_PINMASK_2 ); GPIO_Digital_Output( &GPIOA_BASE, _GPIO_PINMASK_0 ); GPIO_Digital_Input( &GPIOA_BASE, _GPIO_PINMASK_4 ); //UART UART1_Init(9600); Delay_ms(100); UART1_Write_Text( "Starting\r\n" ); // Initialize UART module at 9600 bps // Wait for UART module to stabilize //ADC //ADC1_Init(); //For direct analog values Delay_ms(200); UART1_Write_Text( "UART Initialized\r\n" ); SPI3_Init_Advanced( _SPI_FPCLK_DIV4, _SPI_MASTER | _SPI_8_BIT | _SPI_CLK_IDLE_LOW | _SPI_SECOND_CLK_EDGE_TRANSITION | _SPI_MSB_FIRST | _SPI_SS_DISABLE | _SPI_SSM_ENABLE | _SPI_SSI_1, &_GPIO_MODULE_SPI3_PC10_11_12 ); Delay_ms( 200 ); UART1_Write_Text( "SPI Initialized\r\n" ); } r_meter_init(); UART1_Write_Text( "R Meter Initialized\r\n" ); Code examples that demonstrate the usage of R Meter click with MikroElektronika hardware, written for mikroC for ARM, AVR, dsPIC, FT90x, PIC and PIC32 are available on Libstock (http://libstock.mikroe.com/projects/view/1905/r-meter-click). Resources - R Meter click Libstock example (http://libstock.mikroe.com/projects/view/1905/r-meter-click) - mikroBUS™ standard specifications (http://download.mikroe.com/documents/standards/mikrobus/mikrobus-standard-specification-v200.pdf) http://docs.mikroe.com/R_Meter_click 9/15/2016