From 396c7852e7fc8c5e95190a814cab7c590bc48242 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?King=20K=C3=A9vin?= Date: Tue, 26 Mar 2019 18:01:13 +0100 Subject: [PATCH] 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 --- lib/i2c_master.c | 45 ++++++++++++++++++++++++++++++++++++--------- lib/i2c_master.h | 2 +- 2 files changed, 37 insertions(+), 10 deletions(-) diff --git a/lib/i2c_master.c b/lib/i2c_master.c index fc392da..a47590e 100644 --- a/lib/i2c_master.c +++ b/lib/i2c_master.c @@ -15,7 +15,7 @@ /** library to communicate using I2C as master (code) * @file i2c_master.c * @author King Kévin - * @date 2017-2018 + * @date 2017-2019 * @note peripherals used: I2C */ @@ -24,6 +24,7 @@ #include // general utilities /* STM32 (including CM3) libraries */ +#include // SysTick library #include // real-time control clock library #include // general purpose input output library #include // 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) diff --git a/lib/i2c_master.h b/lib/i2c_master.h index f4e4933..65b4c98 100644 --- a/lib/i2c_master.h +++ b/lib/i2c_master.h @@ -15,7 +15,7 @@ /** library to communicate using I2C as master (API) * @file i2c_master.h * @author King Kévin - * @date 2017-2018 + * @date 2017-2019 * @note peripherals used: I2C */ #pragma once