[Digi-Key Follow me Issue 3] + Supplement: ESP32C3 controls digital potentiometer and op amp to achieve programmable gain

dql2016

[Digi-Key Follow me Issue 3] + Supplement: ESP32C3 controls digital potentiometer and op amp to achieve programmable gain [Copy link]

 

The AD5270 is an excellent 1024-position, 5 ppm/°C temperature coefficient in rheostat mode, 1% resistor tolerance error, SPI interface, and 50-TP memory digital rheostat.

It combines industry-leading variable resistor performance with non-volatile memory (NVM) and provides 50-time programmable (50-TP) memory. Unlimited adjustments can be made before the resistance value is programmed into the 50-TP memory. These devices do not require any external voltage source to help blow the fuse and provide 50 permanent programming opportunities. During the 50-TP activation, a permanent blow fuse command will fix the wiper position. The SPI interface control timing is as follows:

ESP32C3 is programmed with Arduino and is easy to drive. The test code is as follows:

// AD5270 commands - new digital potentiometer
#define CMD_WR_RDAC        0x01
#define CMD_RD_RDAC        0x02
#define CMD_ST_RDAC        0x03
#define CMD_RST            0x04
#define CMD_RD_MEM         0x05
#define CMD_RD_ADDR        0x06
#define CMD_WR_CTRL        0x07
#define CMD_RD_CTRL        0x08
#define CMD_SHTDN          0x09

void vspi_write_word(const int chip_select, uint16_t data_to_send, const uint8_t bit_order, const uint8_t mode) {
  vspi->beginTransaction(SPISettings(SPI_FREQ_FAST, bit_order, mode));
  digitalWrite(chip_select, LOW);   //pull SS slow to prep other end for transfer
  vspi->transfer16(data_to_send);
  digitalWrite(chip_select, HIGH);  //pull ss high to signify end of data transfer
  vspi->endTransaction();
}

/* Write a 4-bit command and a 10-bit data word */
void AD5270_Write(const int chip_select, uint8_t cmd, uint16_t data){
  uint16_t data_word = ((cmd & 0x0F) << 10) | (data & 0x03FF);
  vspi_write_word(chip_select, data_word, MSBFIRST, SPI_MODE1);
}

/* Enable/disable rheostat value changes */
void AD5270_LockUnlock(const int chip_select, uint8_t lock){
  AD5270_Write(chip_select, CMD_WR_CTRL, lock ? 0 : 0x002);
}

/* Enable/disable hardware shutdown */
void AD5270_Shutdown(const int chip_select, uint8_t shutdown){
  AD5270_Write(chip_select, CMD_SHTDN, shutdown ? 1 : 0);
}

/* Set the value of the digital rheostat - range is 0-0x3FF (0-100kOhm) */
void AD5270_Set(const int chip_select, uint16_t val)
{
  AD5270_Write(chip_select, CMD_WR_RDAC, val);
}

#define CHIP_SEL_MEAS      10   // Chip select pin for measuring digital rheostat potentiometer

void setup() {
  // put your setup code here, to run once:
      // Set voltage measurement gain to 1 (maximum current (5V pk-pk) must be within ADC range)
    AD5270_Shutdown(CHIP_SEL_MEAS, 1);
  AD5270_Set(CHIP_SEL_MEAS, 100);

}

void loop() {
  // put your main code here, to run repeatedly:

}

Wiring diagram and test board:

Effect: