/*
* ads1115.c:
* Extend wiringPi with the ADS1115 I2C 16-bit ADC
* Copyright (c) 2016 Gordon Henderson
***********************************************************************
* This file is part of wiringPi:
* https://projects.drogon.net/raspberry-pi/wiringpi/
*
* wiringPi is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* wiringPi is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with wiringPi.
* If not, see .
***********************************************************************
*/
/*
*********************************************************************************
* We're going to work in a hybrid mode to fit in with the wiringPi way of
* doing things, so there will be 4 analog pin which read the 4 single-ended
* channels as usual, also some fake digitalOutputs - these are the control
* registers that allow the user to put it into single/diff mode, set the
* gain and data rates.
*********************************************************************************
*/
#include
#include
#include
#include
#include
#include "ads1115.h"
// Bits in the config register (it's a 16-bit register)
#define CONFIG_OS_MASK (0x8000) // Operational Status Register
#define CONFIG_OS_SINGLE (0x8000) // Write - Starts a single-conversion
// Read 1 = Conversion complete
// The multiplexor
#define CONFIG_MUX_MASK (0x7000)
// Differential modes
#define CONFIG_MUX_DIFF_0_1 (0x0000) // Pos = AIN0, Neg = AIN1 (default)
#define CONFIG_MUX_DIFF_0_3 (0x1000) // Pos = AIN0, Neg = AIN3
#define CONFIG_MUX_DIFF_1_3 (0x2000) // Pos = AIN1, Neg = AIN3
#define CONFIG_MUX_DIFF_2_3 (0x3000) // Pos = AIN2, Neg = AIN3 (2nd differential channel)
// Single-ended modes
#define CONFIG_MUX_SINGLE_0 (0x4000) // AIN0
#define CONFIG_MUX_SINGLE_1 (0x5000) // AIN1
#define CONFIG_MUX_SINGLE_2 (0x6000) // AIN2
#define CONFIG_MUX_SINGLE_3 (0x7000) // AIN3
// Programmable Gain Amplifier
#define CONFIG_PGA_MASK (0x0E00)
#define CONFIG_PGA_6_144V (0x0000) // +/-6.144V range = Gain 2/3
#define CONFIG_PGA_4_096V (0x0200) // +/-4.096V range = Gain 1
#define CONFIG_PGA_2_048V (0x0400) // +/-2.048V range = Gain 2 (default)
#define CONFIG_PGA_1_024V (0x0600) // +/-1.024V range = Gain 4
#define CONFIG_PGA_0_512V (0x0800) // +/-0.512V range = Gain 8
#define CONFIG_PGA_0_256V (0x0A00) // +/-0.256V range = Gain 16
#define CONFIG_MODE (0x0100) // 0 is continuous, 1 is single-shot (default)
// Data Rate
#define CONFIG_DR_MASK (0x00E0)
#define CONFIG_DR_8SPS (0x0000) // 8 samples per second
#define CONFIG_DR_16SPS (0x0020) // 16 samples per second
#define CONFIG_DR_32SPS (0x0040) // 32 samples per second
#define CONFIG_DR_64SPS (0x0060) // 64 samples per second
#define CONFIG_DR_128SPS (0x0080) // 128 samples per second (default)
#define CONFIG_DR_475SPS (0x00A0) // 475 samples per second
#define CONFIG_DR_860SPS (0x00C0) // 860 samples per second
// Comparator mode
#define CONFIG_CMODE_MASK (0x0010)
#define CONFIG_CMODE_TRAD (0x0000) // Traditional comparator with hysteresis (default)
#define CONFIG_CMODE_WINDOW (0x0010) // Window comparator
// Comparator polarity - the polarity of the output alert/rdy pin
#define CONFIG_CPOL_MASK (0x0008)
#define CONFIG_CPOL_ACTVLOW (0x0000) // Active low (default)
#define CONFIG_CPOL_ACTVHI (0x0008) // Active high
// Latching comparator - does the alert/rdy pin latch
#define CONFIG_CLAT_MASK (0x0004)
#define CONFIG_CLAT_NONLAT (0x0000) // Non-latching comparator (default)
#define CONFIG_CLAT_LATCH (0x0004) // Latching comparator
// Comparitor queue
#define CONFIG_CQUE_MASK (0x0003)
#define CONFIG_CQUE_1CONV (0x0000) // Assert after one conversions
#define CONFIG_CQUE_2CONV (0x0001) // Assert after two conversions
#define CONFIG_CQUE_4CONV (0x0002) // Assert after four conversions
#define CONFIG_CQUE_NONE (0x0003) // Disable the comparator (default)
#define CONFIG_DEFAULT (0x8583) // From the datasheet
static const uint16_t dataRates [8] =
{
CONFIG_DR_8SPS, CONFIG_DR_16SPS, CONFIG_DR_32SPS, CONFIG_DR_64SPS, CONFIG_DR_128SPS, CONFIG_DR_475SPS, CONFIG_DR_860SPS
} ;
static const uint16_t gains [6] =
{
CONFIG_PGA_6_144V, CONFIG_PGA_4_096V, CONFIG_PGA_2_048V, CONFIG_PGA_1_024V, CONFIG_PGA_0_512V, CONFIG_PGA_0_256V
} ;
/*
* analogRead:
* Pin is the channel to sample on the device.
* Channels 0-3 are single ended inputs,
* channels 4-7 are the various differential combinations.
*********************************************************************************
*/
static int myAnalogRead (struct wiringPiNodeStruct *node, int pin)
{
int chan = pin - node->pinBase ;
int16_t result ;
uint16_t config = CONFIG_DEFAULT ;
chan &= 7 ;
// Setup the configuration register
// Set PGA/voltage range
config &= ~CONFIG_PGA_MASK ;
config |= node->data0 ;
// Set sample speed
config &= ~CONFIG_DR_MASK ;
config |= node->data1 ;
// Set single-ended channel or differential mode
config &= ~CONFIG_MUX_MASK ;
switch (chan)
{
case 0: config |= CONFIG_MUX_SINGLE_0 ; break ;
case 1: config |= CONFIG_MUX_SINGLE_1 ; break ;
case 2: config |= CONFIG_MUX_SINGLE_2 ; break ;
case 3: config |= CONFIG_MUX_SINGLE_3 ; break ;
case 4: config |= CONFIG_MUX_DIFF_0_1 ; break ;
case 5: config |= CONFIG_MUX_DIFF_2_3 ; break ;
case 6: config |= CONFIG_MUX_DIFF_0_3 ; break ;
case 7: config |= CONFIG_MUX_DIFF_1_3 ; break ;
}
// Start a single conversion
config |= CONFIG_OS_SINGLE ;
config = __bswap_16 (config) ;
wiringPiI2CWriteReg16 (node->fd, 1, config) ;
// Wait for the conversion to complete
for (;;)
{
result = wiringPiI2CReadReg16 (node->fd, 1) ;
result = __bswap_16 (result) ;
if ((result & CONFIG_OS_MASK) != 0)
break ;
delayMicroseconds (100) ;
}
result = wiringPiI2CReadReg16 (node->fd, 0) ;
result = __bswap_16 (result) ;
// Sometimes with a 0v input on a single-ended channel the internal 0v reference
// can be higher than the input, so you get a negative result...
if ( (chan < 4) && (result < 0) )
return 0 ;
else
return (int)result ;
}
/*
* digitalWrite:
* It may seem odd to have a digital write here, but it's the best way
* to pass paramters into the chip in the wiringPi way of things.
* We have 2 digital registers:
* 0 is the gain control
* 1 is the data rate control
*********************************************************************************
*/
static void myDigitalWrite (struct wiringPiNodeStruct *node, int pin, int data)
{
int chan = pin - node->pinBase ;
chan &= 3 ;
if (chan == 0) // Gain Control
{
if ( (data < 0) || (data > 6) ) // Use default if out of range
data = 2 ;
node->data0 = gains [data] ;
}
else // Data rate control
{
if ( (data < 0) || (data > 7) ) // Use default if out of range
data = 4 ;
node->data1 = dataRates [data] ; // Bugfix 0-1 by "Eric de jong (gm)" - Thanks.
}
}
/*
* analogWrite:
* We're using this to write to the 2 comparitor threshold registers.
* We could use a digitalWrite here but as it's an analog comparison
* then it feels better to do it this way.
*********************************************************************************
*/
static void myAnalogWrite (struct wiringPiNodeStruct *node, int pin, int data)
{
int chan = pin - node->pinBase ;
int reg ;
int16_t ndata ;
chan &= 3 ;
reg = chan + 2 ;
/**/ if (data < -32767)
ndata = -32767 ;
else if (data > 32767)
ndata = 32767 ;
else
ndata = (int16_t)data ;
ndata = __bswap_16 (ndata) ;
wiringPiI2CWriteReg16 (node->fd, reg, data) ;
}
/*
* ads1115Setup:
* Create a new wiringPi device node for an ads1115 on the Pi's
* I2C interface.
*********************************************************************************
*/
int ads1115Setup (const int pinBase, int i2cAddr)
{
struct wiringPiNodeStruct *node ;
int fd ;
if ((fd = wiringPiI2CSetup (i2cAddr)) < 0)
return FALSE ;
node = wiringPiNewNode (pinBase, 8) ;
node->fd = fd ;
node->data0 = CONFIG_PGA_4_096V ; // Gain in data0
node->data1 = CONFIG_DR_128SPS ; // Samples/sec in data1
node->analogRead = myAnalogRead ;
node->analogWrite = myAnalogWrite ;
node->digitalWrite = myDigitalWrite ;
return TRUE ;
}