ADS1X1X I2C Driver

A Mongoose library for various I2C speaking ADCs from Texas Instruments:

• ADS1115 - 16bit, 860 Samples/sec, 2 differential / 4 single-ended, programmable gain
• ADS1114 - 16bit, 860 Samples/sec, 1 differential / 1 single-ended, programmable gain
• ADS1113 - 16bit, 860 Samples/sec, 1 differential / 1 single-ended, no gain
• ADS1015 - 12bit, 3300 Samples/sec, 2 differential / 4 single-ended, programmable gain
• ADS1014 - 12bit, 3300 Samples/sec, 1 differential / 1 single-ended, programmable gain
• ADS1013 - 12bit, 3300 Samples/sec, 1 differential / 1 single-ended, no gain.

The most common are the ADS1115 and ADS1015 chips.

Implementation details

The driver takes care of exposing the correct fuctionality based on which type is created. Differential measurements can be taken on all devices, but only ADS1x15 has multiple options.

API Description

First, create a device using mgos_ads1x1x_create() by specifying the type of chip you're using. Take some measurements using mgos_ads1x1x_read(), and clean up the driver by using mgos_ads1x1x_destroy().

mgos_ads1x1x_set_fsr() is used to set the full scale range (FSR) of the ADC. Each chip supports ranges from 6.144 Volts down to 0.256 Volts. You can read the current FSR with mgos_ads1x1x_get_fsr().

mgos_ads1x1x_set_dr() is used to set the data rate of continuous measurements. The support differs between ADS101X (the 12-bit version, which is faster), and ADS111X (the 16-bit version, which is slower). You can read the current DR with mgos_ads1x1x_get_dr().

mgos_ads1x1x_read() starts a singleshot measurement on the given channel (which takes 1ms for ADS101X and 8ms for ADS111X), and returns a 16 bit signed value. The datasheet mentions that with input voltages around GND, a negative value might be returned (ie -2 rather than 0).

mgos_ads1x1x_read_diff() starts a singleshot measurement of the differential voltage between two channels, typically Chan0 and Chan1. Several channel pairs are allowed, see the include file for details. Note, that this function is only available on ADS1X15 chips.

Example application

#include "mgos.h"
#include "mgos_config.h"
#include "mgos_ads1x1x.h"

void timer_cb(void *data) {
  struct mgos_ads1x1x *d = (struct mgos_ads1x1x *)data;
  int16_t res[4];

  if (!d) return;

  for(int i=0; i<4; i++) {
    if (!mgos_ads1x1x_read(s_adc, i, &res[i])) {
      LOG(LL_ERROR, ("Could not read device"));
      return;
    }
  }
  LOG(LL_INFO, ("chan={%6d, %6d, %6d, %6d}", res[0], res[1], res[2], res[3]));
}

enum mgos_app_init_result mgos_app_init(void) {
  struct mgos_ads1x1x *d = NULL;

  if (!(d = mgos_ads1x1x_create(mgos_i2c_get_global(), 0x48, ADC_ADS1115))) {
    LOG(LL_ERROR, ("Could not create ADS1115"));
    return MGOS_APP_INIT_ERROR;
  }

  mgos_set_timer(100, true, timer_cb, d);

  return MGOS_APP_INIT_SUCCESS;
}

Disclaimer

This project is not an official Google project. It is not supported by Google and Google specifically disclaims all warranties as to its quality, merchantability, or fitness for a particular purpose.