Adafruit GP8403

This is the Adafruit GP8403 dual-channel 12-bit voltage-output DAC library.

Tested and works great with the Adafruit GP8403 Breakout Board.

The GP8403 provides two analog voltage outputs with selectable 0-5 V and 0-10 V ranges. This chip uses I2C to communicate, so two pins are required to interface.

Adafruit invests time and resources providing this open source code. Please support Adafruit and open-source hardware by purchasing products from Adafruit!

Written by Limor Fried for Adafruit Industries.

MIT license, check LICENSE for more information.

All text above must be included in any redistribution.

To install, use the Arduino Library Manager and search for "Adafruit GP8403".

Dependencies

This library depends on Adafruit BusIO. Arduino Library Manager will install it automatically.

Wiring

Connect the GP8403 SDA and SCL pins to the corresponding I2C pins on your Arduino, and connect the grounds. The default I2C address is 0x58. Pass a different address to begin() if required by your hardware.

Warning: The GP8403 outputs can reach 10 V. Protect low-voltage ADCs and other downstream inputs with a correctly sized voltage divider or another suitable interface. The library never selects 10 V mode automatically.

Basic use

#include <Adafruit_GP8403.h>

Adafruit_GP8403 gp8403;

void setup() {
  if (!gp8403.begin()) {
    while (1) {
      delay(10);
    }
  }

  gp8403.setOutputRange(GP8403_RANGE_5V);
  gp8403.setVoltage(0, 2.5);
}

void loop() {}

See the examples folder for single-output, dual-output, waveform, 5 V, 10 V, and nonvolatile-memory examples.

begin() checks for the selected I2C address, selects the 5 V range, and sets both outputs to 0 V. Changing the output range also clears both outputs before sending the range command. This prevents an existing DAC code from unexpectedly producing twice the voltage when changing from 5 V to 10 V mode.

getOutputRange(), getRaw(), and getVoltage() return the library's cached requested state. They are not hardware readback because the GP8403 does not provide readable registers.

Invalid channels, raw values above 4095, non-finite voltages, negative voltages, and voltages above the selected range are rejected without an I2C write.

Nonvolatile memory

saveToNVM(SDA, SCL) asks the GP8403 to save its current hardware output state. Saving is never automatic. Do not call it repeatedly or from a loop; the datasheet does not specify the nonvolatile-memory endurance.

Release the I2C peripheral before saving, then restore it afterward. ESP8266 is the exception because its software I2C core does not provide Wire.end():

#ifndef ESP8266
Wire.end();
#endif
bool saved = gp8403.saveToNVM(SDA, SCL);
Wire.begin();

On ESP8266, saveToNVM() takes control of SDA and SCL directly.

If your application uses custom pins, speed, or other bus settings, restore the same configuration instead of using the parameterless Wire.begin() shown above.

The GP8403 uses a special open-drain waveform for nonvolatile-memory programming; it cannot be sent as a normal Wire transaction. The library generates that waveform on the supplied SDA and SCL pins and uses the datasheet's fixed 0x58 programming address. A true result confirms that the programming waveform and acknowledgments completed. Verify persistence after an actual power cycle.

The saved output voltage is restored as soon as the GP8403 powers up. Calling begin() afterward intentionally replaces it by selecting the 5 V range and setting both outputs to 0 V. Applications that need the restored output must use or inspect it before calling begin().