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099f3a4147
I2C slave might stil have something to send when ESP826 starts I2C, thus
keeping the bus stuck.
Happens e.g. when power failure/reset during transmission.
Thanks to work of drmpf there is a solution.
Implemented as separate method so as not to interfere with existing.
Usage:
Wire.begin();
if (Wire.status() != I2C_OK) Serial.writeln("Something wrong with I2C
bus that cannot be recovered. Perform power cycle or search for other
masters on bus.";
214 lines
6.4 KiB
C
214 lines
6.4 KiB
C
/*
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si2c.c - Software I2C library for esp8266
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Copyright (c) 2015 Hristo Gochkov. All rights reserved.
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This file is part of the esp8266 core for Arduino environment.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "twi.h"
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#include "pins_arduino.h"
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#include "wiring_private.h"
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unsigned char twi_dcount = 18;
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static unsigned char twi_sda, twi_scl;
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static uint32_t twi_clockStretchLimit;
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#define SDA_LOW() (GPES = (1 << twi_sda)) //Enable SDA (becomes output and since GPO is 0 for the pin, it will pull the line low)
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#define SDA_HIGH() (GPEC = (1 << twi_sda)) //Disable SDA (becomes input and since it has pullup it will go high)
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#define SDA_READ() ((GPI & (1 << twi_sda)) != 0)
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#define SCL_LOW() (GPES = (1 << twi_scl))
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#define SCL_HIGH() (GPEC = (1 << twi_scl))
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#define SCL_READ() ((GPI & (1 << twi_scl)) != 0)
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#ifndef FCPU80
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#define FCPU80 80000000L
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#endif
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#if F_CPU == FCPU80
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#define TWI_CLOCK_STRETCH_MULTIPLIER 3
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#else
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#define TWI_CLOCK_STRETCH_MULTIPLIER 6
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#endif
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void twi_setClock(unsigned int freq){
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#if F_CPU == FCPU80
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if(freq <= 100000) twi_dcount = 19;//about 100KHz
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else if(freq <= 200000) twi_dcount = 8;//about 200KHz
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else if(freq <= 300000) twi_dcount = 3;//about 300KHz
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else if(freq <= 400000) twi_dcount = 1;//about 400KHz
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else twi_dcount = 1;//about 400KHz
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#else
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if(freq <= 100000) twi_dcount = 32;//about 100KHz
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else if(freq <= 200000) twi_dcount = 14;//about 200KHz
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else if(freq <= 300000) twi_dcount = 8;//about 300KHz
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else if(freq <= 400000) twi_dcount = 5;//about 400KHz
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else if(freq <= 500000) twi_dcount = 3;//about 500KHz
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else if(freq <= 600000) twi_dcount = 2;//about 600KHz
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else twi_dcount = 1;//about 700KHz
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#endif
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}
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void twi_setClockStretchLimit(uint32_t limit){
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twi_clockStretchLimit = limit * TWI_CLOCK_STRETCH_MULTIPLIER;
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}
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void twi_init(unsigned char sda, unsigned char scl){
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twi_sda = sda;
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twi_scl = scl;
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pinMode(twi_sda, INPUT_PULLUP);
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pinMode(twi_scl, INPUT_PULLUP);
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twi_setClock(100000);
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twi_setClockStretchLimit(230); // default value is 230 uS
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}
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void twi_stop(void){
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pinMode(twi_sda, INPUT);
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pinMode(twi_scl, INPUT);
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}
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static void twi_delay(unsigned char v){
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unsigned int i;
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wunused-but-set-variable"
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unsigned int reg;
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for(i=0;i<v;i++) reg = GPI;
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#pragma GCC diagnostic pop
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}
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static bool twi_write_start(void) {
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SCL_HIGH();
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SDA_HIGH();
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if (SDA_READ() == 0) return false;
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twi_delay(twi_dcount);
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SDA_LOW();
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twi_delay(twi_dcount);
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return true;
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}
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static bool twi_write_stop(void){
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uint32_t i = 0;
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SCL_LOW();
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SDA_LOW();
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twi_delay(twi_dcount);
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SCL_HIGH();
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while (SCL_READ() == 0 && (i++) < twi_clockStretchLimit); // Clock stretching
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twi_delay(twi_dcount);
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SDA_HIGH();
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twi_delay(twi_dcount);
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return true;
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}
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static bool twi_write_bit(bool bit) {
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uint32_t i = 0;
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SCL_LOW();
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if (bit) SDA_HIGH();
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else SDA_LOW();
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twi_delay(twi_dcount+1);
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SCL_HIGH();
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while (SCL_READ() == 0 && (i++) < twi_clockStretchLimit);// Clock stretching
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twi_delay(twi_dcount);
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return true;
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}
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static bool twi_read_bit(void) {
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uint32_t i = 0;
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SCL_LOW();
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SDA_HIGH();
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twi_delay(twi_dcount+2);
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SCL_HIGH();
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while (SCL_READ() == 0 && (i++) < twi_clockStretchLimit);// Clock stretching
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bool bit = SDA_READ();
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twi_delay(twi_dcount);
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return bit;
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}
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static bool twi_write_byte(unsigned char byte) {
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unsigned char bit;
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for (bit = 0; bit < 8; bit++) {
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twi_write_bit(byte & 0x80);
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byte <<= 1;
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}
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return !twi_read_bit();//NACK/ACK
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}
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static unsigned char twi_read_byte(bool nack) {
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unsigned char byte = 0;
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unsigned char bit;
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for (bit = 0; bit < 8; bit++) byte = (byte << 1) | twi_read_bit();
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twi_write_bit(nack);
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return byte;
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}
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unsigned char twi_writeTo(unsigned char address, unsigned char * buf, unsigned int len, unsigned char sendStop){
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unsigned int i;
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if(!twi_write_start()) return 4;//line busy
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if(!twi_write_byte(((address << 1) | 0) & 0xFF)) {
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if (sendStop) twi_write_stop();
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return 2; //received NACK on transmit of address
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}
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for(i=0; i<len; i++) {
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if(!twi_write_byte(buf[i])) {
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if (sendStop) twi_write_stop();
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return 3;//received NACK on transmit of data
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}
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}
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if(sendStop) twi_write_stop();
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i = 0;
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while(SDA_READ() == 0 && (i++) < 10){
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SCL_LOW();
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twi_delay(twi_dcount);
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SCL_HIGH();
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twi_delay(twi_dcount);
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}
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return 0;
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}
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unsigned char twi_readFrom(unsigned char address, unsigned char* buf, unsigned int len, unsigned char sendStop){
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unsigned int i;
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if(!twi_write_start()) return 4;//line busy
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if(!twi_write_byte(((address << 1) | 1) & 0xFF)) {
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if (sendStop) twi_write_stop();
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return 2;//received NACK on transmit of address
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}
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for(i=0; i<(len-1); i++) buf[i] = twi_read_byte(false);
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buf[len-1] = twi_read_byte(true);
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if(sendStop) twi_write_stop();
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i = 0;
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while(SDA_READ() == 0 && (i++) < 10){
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SCL_LOW();
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twi_delay(twi_dcount);
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SCL_HIGH();
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twi_delay(twi_dcount);
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}
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return 0;
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}
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uint8_t twi_status(){
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if (SCL_READ()==0) return I2C_SCL_HELD_LOW; //SCL held low by another device, no procedure available to recover
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int clockCount = 20;
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while (SDA_READ()==0 && clockCount>0){ //if SDA low, read the bits slaves have to sent to a max
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twi_read_bit();
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if (SCL_READ()==0) return I2C_SCL_HELD_LOW_AFTER_READ; //I2C bus error. SCL held low beyond slave clock stretch time
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}
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if (SDA_READ()==0) return I2C_SDA_HELD_LOW; //I2C bus error. SDA line held low by slave/another_master after n bits.
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if(!twi_write_start()) return I2C_SDA_HELD_LOW_AFTER_INIT; //line busy. SDA again held low by another device. 2nd master?
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else return I2C_OK; //all ok
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} |