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209 lines
6.5 KiB
209 lines
6.5 KiB
/*
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I2C MODULE
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Copyright (C) 2017-2018 by Xose Pérez <xose dot perez at gmail dot com>
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*/
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#if I2C_SUPPORT
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unsigned int _i2c_locked[16] = {0};
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#if I2C_USE_BRZO
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#include "brzo_i2c.h"
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unsigned long _i2c_scl_frequency = 0;
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#else
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#include "Wire.h"
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#endif
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// -----------------------------------------------------------------------------
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// Private
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// -----------------------------------------------------------------------------
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int _i2cClearbus(int sda, int scl) {
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#if defined(TWCR) && defined(TWEN)
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// Disable the Atmel 2-Wire interface so we can control the SDA and SCL pins directly
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TWCR &= ~(_BV(TWEN));
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#endif
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// Make SDA (data) and SCL (clock) pins inputs with pullup
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pinMode(sda, INPUT_PULLUP);
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pinMode(scl, INPUT_PULLUP);
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delay(2500);
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// Wait 2.5 secs. This is strictly only necessary on the first power
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// up of the DS3231 module to allow it to initialize properly,
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// but is also assists in reliable programming of FioV3 boards as it gives the
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// IDE a chance to start uploaded the program
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// before existing sketch confuses the IDE by sending Serial data.
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// If it is held low the device cannot become the I2C master
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// I2C bus error. Could not clear SCL clock line held low
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boolean scl_low = (digitalRead(scl) == LOW);
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if (scl_low) return 1;
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boolean sda_low = (digitalRead(sda) == LOW);
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int clockCount = 20; // > 2x9 clock
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// While SDA is low for at most 20 cycles
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while (sda_low && (clockCount > 0)) {
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clockCount--;
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// Note: I2C bus is open collector so do NOT drive SCL or SDA high
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pinMode(scl, INPUT); // release SCL pullup so that when made output it will be LOW
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pinMode(scl, OUTPUT); // then clock SCL Low
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delayMicroseconds(10); // for >5uS
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pinMode(scl, INPUT); // release SCL LOW
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pinMode(scl, INPUT_PULLUP); // turn on pullup resistors again
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// do not force high as slave may be holding it low for clock stretching
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delayMicroseconds(10); // The >5uS is so that even the slowest I2C devices are handled
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// loop waiting for SCL to become high only wait 2sec
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scl_low = (digitalRead(scl) == LOW);
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int counter = 20;
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while (scl_low && (counter > 0)) {
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counter--;
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delay(100);
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scl_low = (digitalRead(scl) == LOW);
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}
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// If still low after 2 sec error
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// I2C bus error. Could not clear. SCL clock line held low by slave clock stretch for >2sec
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if (scl_low) return 2;
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sda_low = (digitalRead(sda) == LOW); // and check SDA input again and loop
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}
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// If still low
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// I2C bus error. Could not clear. SDA data line held low
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if (sda_low) return 3;
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// Pull SDA line low for "start" or "repeated start"
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pinMode(sda, INPUT); // remove pullup
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pinMode(sda, OUTPUT); // and then make it LOW i.e. send an I2C Start or Repeated start control
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// When there is only one I2C master a "start" or "repeat start" has the same function as a "stop" and clears the bus
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// A Repeat Start is a Start occurring after a Start with no intervening Stop.
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delayMicroseconds(10); // wait >5uS
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pinMode(sda, INPUT); // remove output low
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pinMode(sda, INPUT_PULLUP); // and make SDA high i.e. send I2C STOP control.
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delayMicroseconds(10); // wait >5uS
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pinMode(sda, INPUT); // and reset pins as tri-state inputs which is the default state on reset
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pinMode(scl, INPUT);
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// Everything OK
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return 0;
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}
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// -----------------------------------------------------------------------------
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// Utils
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// -----------------------------------------------------------------------------
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void i2cClearBus() {
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unsigned char sda = getSetting("i2cSDA", I2C_SDA_PIN).toInt();
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unsigned char scl = getSetting("i2cSCL", I2C_SCL_PIN).toInt();
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DEBUG_MSG_P(PSTR("[I2C] Clear bus (response: %d)\n"), _i2cClearbus(sda, scl));
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}
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bool i2cCheck(unsigned char address) {
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#if I2C_USE_BRZO
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brzo_i2c_start_transaction(address, _i2c_scl_frequency);
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brzo_i2c_ACK_polling(1000);
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return brzo_i2c_end_transaction();
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#else
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Wire.beginTransmission(address);
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return Wire.endTransmission();
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#endif
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}
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bool i2cGetLock(unsigned char address) {
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unsigned char index = address / 8;
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unsigned char mask = 1 << (address % 8);
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if (_i2c_locked[index] & mask) return false;
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_i2c_locked[index] = _i2c_locked[index] | mask;
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DEBUG_MSG_P(PSTR("[I2C] Address 0x%02X locked\n"), address);
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return true;
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}
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bool i2cReleaseLock(unsigned char address) {
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unsigned char index = address / 8;
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unsigned char mask = 1 << (address % 8);
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if (_i2c_locked[index] & mask) {
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_i2c_locked[index] = _i2c_locked[index] & ~mask;
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return true;
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}
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return false;
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}
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unsigned char i2cFind(size_t size, unsigned char * addresses, unsigned char &start) {
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for (unsigned char i=start; i<size; i++) {
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if (i2cCheck(addresses[i]) == 0) {
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start = i;
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return addresses[i];
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}
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}
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return 0;
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}
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unsigned char i2cFind(size_t size, unsigned char * addresses) {
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unsigned char start = 0;
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return i2cFind(size, addresses, start);
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}
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unsigned char i2cFindAndLock(size_t size, unsigned char * addresses) {
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unsigned char start = 0;
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unsigned char address = 0;
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while (address = i2cFind(size, addresses, start)) {
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if (i2cGetLock(address)) break;
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start++;
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}
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return address;
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}
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void i2cScan() {
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unsigned char nDevices = 0;
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for (unsigned char address = 1; address < 127; address++) {
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unsigned char error = i2cCheck(address);
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if (error == 0) {
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DEBUG_MSG_P(PSTR("[I2C] Device found at address 0x%02X\n"), address);
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nDevices++;
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}
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}
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if (nDevices == 0) DEBUG_MSG_P(PSTR("[I2C] No devices found\n"));
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}
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void i2cSetup() {
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unsigned char sda = getSetting("i2cSDA", I2C_SDA_PIN).toInt();
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unsigned char scl = getSetting("i2cSCL", I2C_SCL_PIN).toInt();
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#if I2C_USE_BRZO
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unsigned long cst = getSetting("i2cCST", I2C_CLOCK_STRETCH_TIME).toInt();
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_i2c_scl_frequency = getSetting("i2cFreq", I2C_SCL_FREQUENCY).toInt();
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brzo_i2c_setup(sda, scl, cst);
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#else
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Wire.begin(sda, scl);
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#endif
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DEBUG_MSG_P(PSTR("[I2C] Using GPIO%u for SDA and GPIO%u for SCL\n"), sda, scl);
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#if I2C_CLEAR_BUS
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i2cClearBus();
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#endif
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#if I2C_PERFORM_SCAN
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i2cScan();
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#endif
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}
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#endif
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