ADS1X1X I2C

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mongoose-os-libs/ads1x1x-i2c	mgos_ads1x1x.h

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.

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mgos_ads1x1x_create

struct mgos_ads1x1x *mgos_ads1x1x_create(struct mgos_i2c *i2c, uint8_t i2caddr, enum mgos_ads1x1x_type type);

Initialize a ADS1X1X on the I2C bus i2c at address specified in i2caddr parameter (default ADS1X1X is on address 0x48). The device will be polled for validity, upon success a new struct mgos_ads1x1x is allocated and returned. If the device could not be found, NULL is returned.

mgos_ads1x1x_destroy

bool mgos_ads1x1x_destroy(struct mgos_ads1x1x **dev);

Destroy the data structure associated with a ADS1X1X device. The reference to the pointer of the struct mgos_ads1x1x has to be provided, and upon successful destruction, its associated memory will be freed and the pointer set to NULL and true will be returned.

mgos_ads1x1x_set_fsr

bool mgos_ads1x1x_set_fsr(struct mgos_ads1x1x *dev, enum mgos_ads1x1x_fsr fsr);
bool mgos_ads1x1x_get_fsr(struct mgos_ads1x1x *dev, enum mgos_ads1x1x_fsr *fsr);

Get or Set the Full Scale Range (FSR). All chips in the ADS1X1X family support the same settings. By default, 2.048V is used.

Note: ADS1x13 does not support this, and always has an FSR of 2.048V.

Returns true on success, false otherwise.

mgos_ads1x1x_set_dr

bool mgos_ads1x1x_set_dr(struct mgos_ads1x1x *dev, enum mgos_ads1x1x_dr dr);
bool mgos_ads1x1x_get_dr(struct mgos_ads1x1x *dev, enum mgos_ads1x1x_dr *dr);

Get or Set the Data Rate (in Samples per Second). If the supplied dr argument cannot be set on the chip, false is returned. Otherwise, the supplied dr is set. By default, ADS101X sets 1600SPS, ADS111X sets 128SPS.

Returns true on success, false otherwise.

mgos_ads1x1x_read

bool mgos_ads1x1x_read(struct mgos_ads1x1x *dev, uint8_t chan, int16_t *result);

Read a channel from the ADC and return the read value in result. If the channel was invalid, or an error occurred, false is returned and the result cannot be relied upon.

Returns true on success, false otherwise.

mgos_ads1x1x_read_diff

bool mgos_ads1x1x_read_diff(struct mgos_ads1x1x *dev, uint8_t chanP, uint8_t chanN, int16_t *result);

Read a 2-channel differential from the ADC and return the read value in result. If the channel pair invalid, or an error occurred, false is returned and the result cannot be relied upon. Upon success, true is returned.

Note: This is only available on ADS1X15 chips. Valid chanP/chanN pairs are : 0/1, 0/3, 1/3, 2/3.

Returns true on success, false otherwise.

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