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I2C: add timeout to send start condition 

sometimes the internal state f the I2C peripheral is confused,
and sending a start condition is not possible and the
corresponding registers will not be set.
see the errata for more details.
as workaround a timer is used, resetting the I2C is case it times
out
This commit is contained in:
King Kévin 2019-03-26 18:01:13 +01:00
parent 5e13d19bda
commit 396c7852e7
2 changed files with 37 additions and 10 deletions
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45
lib/i2c_master.c
View File

@ -15,7 +15,7 @@
/** library to communicate using I2C as master (code)
* @file i2c_master.c
* @author King Kévin <kingkevin@cuvoodoo.info>
* @date 2017-2018
* @date 2017-2019
* @note peripherals used: I2C
*/
@ -24,6 +24,7 @@
#include <stdlib.h> // general utilities
/* STM32 (including CM3) libraries */
#include <libopencm3/cm3/systick.h> // SysTick library
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/i2c.h> // I2C library
@ -288,24 +289,50 @@ enum i2c_master_rc i2c_master_start(uint32_t i2c)
while (true);
}
bool retry = true; // retry after reset if first try failed
enum i2c_master_rc to_return; // return code
try:
to_return = I2C_MASTER_RC_NONE; // return code
// send (re-)start condition
if (I2C_CR1(i2c) & (I2C_CR1_START|I2C_CR1_STOP)) { // ensure start or stop operations are not in progress
return I2C_MASTER_RC_START_STOP_IN_PROGESS;
}
// prepare timer in case the peripheral hangs on sending stop condition (see errata 2.14.4 Wrong behavior of I2C peripheral in master mode after a misplaced Stop)
systick_counter_disable(); // disable SysTick to reconfigure it
systick_set_frequency(500, rcc_ahb_frequency); // set timer to 2 ms (that should be long enough to send a start condition)
systick_clear(); // reset SysTick (set to 0)
systick_interrupt_disable(); // disable interrupt to prevent ISR to read the flag
systick_get_countflag(); // reset flag (set when counter is going for 1 to 0)
i2c_send_start(i2c); // send start condition to start transaction
while ((I2C_CR1(i2c) & I2C_CR1_START) && !(I2C_SR1(i2c) & (I2C_SR1_BERR|I2C_SR1_ARLO))); // wait until start condition has been accepted and cleared
if (I2C_SR1(i2c) & (I2C_SR1_BERR|I2C_SR1_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
bool timeout = false; // remember if the timeout has been reached
systick_counter_enable(); // start timer
while ((I2C_CR1(i2c) & I2C_CR1_START) && !(I2C_SR1(i2c) & (I2C_SR1_BERR|I2C_SR1_ARLO)) && !timeout) { // wait until start condition has been accepted and cleared
timeout |= systick_get_countflag(); // verify if timeout has been reached
}
while (!(I2C_SR1(i2c) & I2C_SR1_SB) && !(I2C_SR1(i2c) & (I2C_SR1_BERR|I2C_SR1_ARLO))); // wait until start condition is transmitted
if (I2C_SR1(i2c) & (I2C_SR1_BERR|I2C_SR1_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
to_return = I2C_MASTER_RC_BUS_ERROR;
}
if (!(I2C_SR2(i2c) & I2C_SR2_MSL)) { // verify if in master mode
return I2C_MASTER_RC_NOT_MASTER;
while (!(I2C_SR1(i2c) & I2C_SR1_SB) && !(I2C_SR1(i2c) & (I2C_SR1_BERR|I2C_SR1_ARLO)) && !timeout && I2C_MASTER_RC_NONE == to_return) { // wait until start condition is transmitted
timeout |= systick_get_countflag(); // verify if timeout has been reached
}
if (I2C_SR1(i2c) & (I2C_SR1_BERR|I2C_SR1_ARLO)) {
to_return = I2C_MASTER_RC_BUS_ERROR;
} else if (!(I2C_SR1(i2c) & I2C_SR1_SB)) { // the start bit has not been set although we the peripheral is not busy anymore
to_return = I2C_MASTER_RC_BUS_ERROR;
} else if (!(I2C_SR2(i2c) & I2C_SR2_MSL)) { // verify if in master mode
to_return = I2C_MASTER_RC_NOT_MASTER;
} else if (timeout) { // timeout has been reached, i.e. the peripheral hangs
to_return = I2C_MASTER_RC_NOT_MASTER;
}
return I2C_MASTER_RC_NONE;
if (I2C_MASTER_RC_NOT_MASTER == to_return && retry) { // error happened
retry = false; // don't retry a second time
I2C_CR1(i2c) |= I2C_CR1_SWRST; // assert peripheral reset
I2C_CR1(i2c) &= ~I2C_CR1_SWRST; // release peripheral reset
goto try;
}
systick_counter_disable(); // we don't need to timer anymore
return to_return;
}
enum i2c_master_rc i2c_master_select_slave(uint32_t i2c, uint16_t slave, bool address_10bit, bool write)

2
lib/i2c_master.h
View File

@ -15,7 +15,7 @@
/** library to communicate using I2C as master (API)
* @file i2c_master.h
* @author King Kévin <kingkevin@cuvoodoo.info>
* @date 2017-2018
* @date 2017-2019
* @note peripherals used: I2C
*/
#pragma once