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i2c_master: improve flag check and add timeout

This commit is contained in:
King Kévin 2021-08-16 13:21:14 +02:00
parent 55b9e429fa
commit 2bd3c4c0b3
2 changed files with 163 additions and 103 deletions
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262
i2c_master.c
View File

@ -17,20 +17,36 @@
#include "main.h"
bool i2c_master_setup(bool fast)
// timeout for while loops (at least 100 us)
#define TIMEOUT 20000U
static uint16_t timeout;
bool i2c_master_setup(uint16_t freq_khz)
{
// configure I²C peripheral
I2C_CR1 &= ~I2C_CR1_PE; // disable I²C peripheral to configure it
/*
if (!i2c_master_check_signals()) { // check the signal lines
return false;
}
*/
I2C_FREQR = 16; // the peripheral frequency (must match CPU frequency)
if (fast) {
I2C_CCRL = 0x2; // set SCL at 320 kHz (for less error)
I2C_CCRH = (I2C_CCRH_FS | I2C_CCRH_DUTY); // set fast speed mode
I2C_CCRH = (1U << 7); // set fast speed mode
if (freq_khz > 100) {
uint16_t ccr = (I2C_FREQR * 1000) / (3 * freq_khz);
if (ccr > 0x0fff) {
ccr = 0x0fff;
}
I2C_CCRL = (ccr & 0xff); // set SCL at 320 kHz (for less error)
I2C_CCRH = ((ccr >> 8) & 0x0f) | (I2C_CCRH_FS); // set fast speed mode
I2C_TRISER = ((I2C_FREQR * 3 / 10) + 1); // set rise time
} else {
I2C_CCRL = 0x50; // set SCL at 100 kHz
I2C_CCRH = 0; // set standard speed mode
uint16_t ccr = (I2C_FREQR * 1000) / (2 * freq_khz);
if (ccr > 0x0fff) {
ccr = 0x0fff;
}
I2C_CCRL = (ccr & 0xff); // set SCL at 320 kHz (for less error)
I2C_CCRH = ((ccr >> 8) & 0x0f); // set fast speed mode
I2C_TRISER = (I2C_FREQR + 1); // set rise time
}
I2C_CR1 |= I2C_CR1_PE; // enable I²C peripheral
return true;
@ -48,10 +64,10 @@ bool i2c_master_check_signals(void)
GPIO_PB->DDR.reg |= (PB4 | PB5); // set SCL/SDA as output to test pull-up
GPIO_PB->ODR.reg |= PB4; // ensure SCL is high
GPIO_PB->ODR.reg &= ~PB5; // set SDA low (start condition)
for (volatile uint8_t t = 0; t < 10; t++); // wait 10 us
for (volatile uint8_t t = 0; t < 10; t++); // wait a bit to be sure signal is low
GPIO_PB->ODR.reg |= PB5; // set SDA high (stop condition)
for (volatile uint8_t t = 0; t < 10; t++); // wait 10 us for pull-up to take effect
GPIO_PB->DDR.reg &= ~(PB4 | PB5); // set SCL/SDA as input before it is used as alternate function by the peripheral
for (volatile uint8_t t = 0; t < 50; t++); // wait 10 us for pull-up to take effect
return ((GPIO_PB->IDR.reg & PB4) && (GPIO_PB->IDR.reg & PB5)); // test if both lines are up
}
@ -62,10 +78,10 @@ void i2c_master_reset(void)
// don't check if BUSY is cleared since its state might be erroneous
// rewriting I2C_CR2 before I2C_CR2_STOP is cleared might cause a second STOP, but at this point we don't care
I2C_CR2 |= I2C_CR2_SWRST; // reset peripheral, in case we got stuck and the dog bit
// be sure a watchdog is present as this can take forever
while ((0 == (GPIO_PB->IDR.reg & PB4) && (0 == (GPIO_PB->IDR.reg & PB5)))); // wait for SDA/SCL line to be released
I2C_CR2 &= ~I2C_CR2_SWRST; // release reset
I2C_CR1 &= ~I2C_CR1_PE; // disable I²C peripheral to clear some bits
I2C_CR1 |= I2C_CR1_PE; // re-enable I²C peripheral (must be done before any other register is written)
}
enum i2c_master_rc i2c_master_start(void)
@ -74,19 +90,25 @@ enum i2c_master_rc i2c_master_start(void)
if (I2C_CR2 & (I2C_CR2_START | I2C_CR2_STOP)) { // ensure start or stop operations are not in progress
return I2C_MASTER_RC_START_STOP_IN_PROGESS;
}
// don't check BUSY flag as this might be for a re-start
I2C_CR2 |= I2C_CR2_START; // sent start condition
while ((I2C_CR2 & I2C_CR2_START) && !(I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) && !(I2C_CR2 & I2C_CR2_STOP)); // wait until start condition has been accepted and cleared
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (!(I2C_SR1 & I2C_SR1_SB)) { // the start bit has not been set
return I2C_MASTER_RC_BUS_ERROR;
}
if (!(I2C_SR3 & I2C_SR3_MSL)) { // verify if in master mode
return I2C_MASTER_RC_NOT_MASTER;
// in theory, when the START condition is sent, CR2_START is cleared, SR1_SB is set, and SR3_MSL is sent
// in practice this is not synchronous, and the TRM doesn't document it
I2C_SR2 = 0; // clear error flags
timeout = TIMEOUT; // start timeout count
while ((I2C_CR2 & I2C_CR2_START) || !(I2C_SR1 & I2C_SR1_SB) || !(I2C_SR3 & I2C_SR3_MSL)) { // wait until start condition has been accepted, send, and we are in aster mode
if (0 == timeout--) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
}
return I2C_MASTER_RC_NONE;
@ -97,9 +119,15 @@ enum i2c_master_rc i2c_master_start(void)
*/
static enum i2c_master_rc i2c_master_wait_stop(void)
{
while ((I2C_CR2 & I2C_CR2_STOP) && !(I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO))); // wait until stop condition is accepted and cleared
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
I2C_SR2 = 0; // clear error flags
timeout = TIMEOUT; // start timeout counter
while (I2C_CR2 & I2C_CR2_STOP) { // wait until stop condition is accepted and cleared
if (0 == timeout--) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
}
// this time we can't use I2C_CR2_STOP to check for timeout
if (I2C_SR3 & I2C_SR3_MSL) { // ensure we are not in master mode anymore
@ -108,9 +136,11 @@ static enum i2c_master_rc i2c_master_wait_stop(void)
if (I2C_SR3 & I2C_SR3_BUSY) { // ensure bus is released
return I2C_MASTER_RC_BUS_ERROR;
}
/*
if (!i2c_master_check_signals()) { // ensure lines are released
return I2C_MASTER_RC_BUS_ERROR;
}
*/
return I2C_MASTER_RC_NONE;
}
@ -145,52 +175,12 @@ enum i2c_master_rc i2c_master_select_slave(uint16_t slave, bool address_10bit, b
I2C_SR2 &= ~(I2C_SR2_AF); // clear acknowledgement failure
if (!address_10bit) { // 7-bit address
I2C_DR = (slave << 1) | (write ? 0 : 1); // select slave, with read/write flag
while (!(I2C_SR1 & I2C_SR1_ADDR) && !(I2C_SR2 & (I2C_SR2_AF | I2C_SR2_BERR | I2C_SR2_ARLO)) && !(I2C_CR2 & I2C_CR2_STOP)); // wait until address is transmitted (or error)
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // address has not been acknowledged
return I2C_MASTER_RC_NAK;
}
} else { // 10-bit address
// send first part of address
I2C_DR = 11110000 | (((slave >> 8 ) & 0x3) << 1); // send first header (11110xx0, where xx are 2 MSb of slave address)
while (!(I2C_SR1 & I2C_SR1_ADD10) && !(I2C_SR2 & (I2C_SR2_AF | I2C_SR2_BERR | I2C_SR2_ARLO)) && !(I2C_CR2 & I2C_CR2_STOP)); // wait until address is transmitted (or error)
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // address has not been acknowledged
return I2C_MASTER_RC_NAK;
}
// send second part of address
I2C_SR2 &= ~(I2C_SR2_AF); // clear acknowledgement failure
I2C_DR = (slave & 0xff); // send remaining of address
while (!(I2C_SR1 & I2C_SR1_ADDR) && !(I2C_SR2 & (I2C_SR2_AF | I2C_SR2_BERR | I2C_SR2_ARLO)) && !(I2C_CR2 & I2C_CR2_STOP)); // wait until address is transmitted (or error)
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // address has not been acknowledged
return I2C_MASTER_RC_NAK;
}
// go into receive mode if necessary
if (!write) {
enum i2c_master_rc rc = i2c_master_start(); // send start condition
if (I2C_MASTER_RC_NONE != rc) {
return rc;
I2C_SR2 = 0; // clear error flags
timeout = TIMEOUT; // start timeout counter
while (!(I2C_SR1 & I2C_SR1_ADDR)) { // wait until address is transmitted (or error)
if (0 == timeout--) {
return I2C_MASTER_RC_TIMEOUT;
}
// send first part of address with receive flag
I2C_SR2 &= ~(I2C_SR2_AF); // clear acknowledgement failure
I2C_DR = 11110001 | (((slave >> 8) & 0x3) << 1); // send header (11110xx1, where xx are 2 MSb of slave address)
while (!(I2C_SR1 & I2C_SR1_ADDR) && !(I2C_SR2 & (I2C_SR2_AF | I2C_SR2_BERR | I2C_SR2_ARLO)) && !(I2C_CR2 & I2C_CR2_STOP)); // wait until address is transmitted (or error)
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
@ -201,8 +191,74 @@ enum i2c_master_rc i2c_master_select_slave(uint16_t slave, bool address_10bit, b
return I2C_MASTER_RC_NAK;
}
}
} else { // 10-bit address
// send first part of address
I2C_DR = 11110000 | (((slave >> 8 ) & 0x3) << 1); // send first header (11110xx0, where xx are 2 MSb of slave address)
I2C_SR2 = 0; // clear error flags
timeout = TIMEOUT; // start timeout counter
while (!(I2C_SR1 & I2C_SR1_ADD10)) { // wait until address is transmitted (or error)
if (0 == timeout--) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // address has not been acknowledged
return I2C_MASTER_RC_NAK;
}
}
// send second part of address
I2C_SR2 &= ~(I2C_SR2_AF); // clear acknowledgement failure
I2C_DR = (slave & 0xff); // send remaining of address
I2C_SR2 = 0; // clear error flags
timeout = TIMEOUT; // start timeout counter
while (!(I2C_SR1 & I2C_SR1_ADDR)) { // wait until address is transmitted (or error)
if (0 == timeout--) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // address has not been acknowledged
return I2C_MASTER_RC_NAK;
}
}
// go into receive mode if necessary
if (!write) {
enum i2c_master_rc rc = i2c_master_start(); // send start condition
if (I2C_MASTER_RC_NONE != rc) {
return rc;
}
// send first part of address with receive flag
I2C_SR2 &= ~(I2C_SR2_AF); // clear acknowledgement failure
I2C_DR = 11110001 | (((slave >> 8) & 0x3) << 1); // send header (11110xx1, where xx are 2 MSb of slave address)
I2C_SR2 = 0; // clear error flags
timeout = TIMEOUT; // start timeout counter
while (!(I2C_SR1 & I2C_SR1_ADDR)) { // wait until address is transmitted (or error)
if (0 == timeout--) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // address has not been acknowledged
return I2C_MASTER_RC_NAK;
}
}
}
}
// I2C_SR3_TRA should be set after I2C_SR1_ADDR is cleared (end of address transmission), but this is not the case and the TRM/errata does not provide more info
// verify if we are in the right mode
// final check
if (write && !(I2C_SR3 & I2C_SR3_TRA)) {
return I2C_MASTER_RC_NOT_TRANSMIT;
} else if (!write && (I2C_SR3 & I2C_SR3_TRA)) {
@ -225,17 +281,23 @@ enum i2c_master_rc i2c_master_read(uint8_t* data, uint16_t data_size)
}
// read data
I2C_CR2 |= I2C_CR2_ACK; // enable ACK by default
I2C_SR2 = 0; // clear error flags
for (uint16_t i = 0; i < data_size; i++) { // read bytes
IWDG->KR.fields.KEY = IWDG_KR_KEY_REFRESH; // reset watchdog
// set (N)ACK (EV6_3, EV6_1)
if (1 == data_size - i) { // prepare to sent NACK for last byte
if (1 == (data_size - i)) { // prepare to sent NACK for last byte
I2C_CR2 &= ~(I2C_CR2_ACK); // disable ACK
I2C_CR2 |= I2C_CR2_STOP; // prepare to send the stop
} else {
I2C_CR2 |= I2C_CR2_ACK; // enable ACK
}
while (!(I2C_SR1 & I2C_SR1_RXNE) && !(I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO))); // wait until data is received (or error)
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
timeout = TIMEOUT; // start timeout counter
while (!(I2C_SR1 & I2C_SR1_RXNE)) { // wait until data is received (or error)
if (0 == timeout--) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
}
data[i] = I2C_DR; // read the received byte
}
@ -246,7 +308,7 @@ enum i2c_master_rc i2c_master_read(uint8_t* data, uint16_t data_size)
enum i2c_master_rc i2c_master_write(const uint8_t* data, uint16_t data_size)
{
if (NULL == data || 0 == data_size) { // no data to read
return I2C_MASTER_RC_NONE; // we don't indicate an error because the stop is done seperatly
return I2C_MASTER_RC_NONE; // we don't indicate an error because the stop is done separately
}
if (!(I2C_SR3 & I2C_SR3_MSL)) { // I²C device is not in master mode
return I2C_MASTER_RC_NOT_MASTER;
@ -259,27 +321,25 @@ enum i2c_master_rc i2c_master_write(const uint8_t* data, uint16_t data_size)
// write data
for (uint16_t i = 0; i < data_size; i++) { // write bytes
I2C_SR2 &= ~(I2C_SR2_AF); // clear acknowledgement failure
(void)(I2C_SR1 & I2C_SR1_BTF); // clear BTF (when followed by write) in case the clock is stretched because there was no data to send on the next transmission slot
I2C_DR = data[i]; // send byte
while (!(I2C_SR1 & I2C_SR1_TXE) && !(I2C_SR2 & (I2C_SR2_AF | I2C_SR2_BERR | I2C_SR2_ARLO)) && !(I2C_CR2 & I2C_CR2_STOP)); // wait until byte has been transmitted
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
I2C_SR2 = 0; // clear error flags
timeout = TIMEOUT; // start timeout counter
while (!(I2C_SR1 & I2C_SR1_TXE)) { // wait until byte has been transmitted
IWDG->KR.fields.KEY = IWDG_KR_KEY_REFRESH; // reset watchdog
if (0 == timeout--) {
return I2C_MASTER_RC_NOT_MASTER;
}
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // data has not been acknowledged
return I2C_MASTER_RC_NAK;
}
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // data has not been acknowledged
return I2C_MASTER_RC_NAK;
}
}
while (!(I2C_SR1 & I2C_SR1_BTF) && !(I2C_SR2 & (I2C_SR2_AF | I2C_SR2_BERR | I2C_SR2_ARLO)) && !(I2C_CR2 & I2C_CR2_STOP)); // wait until last byte has been transmitted
if (I2C_SR2 & (I2C_SR2_BERR | I2C_SR2_ARLO)) {
return I2C_MASTER_RC_BUS_ERROR;
}
if (I2C_CR2 & I2C_CR2_STOP) {
return I2C_MASTER_RC_TIMEOUT;
}
if (I2C_SR2 & I2C_SR2_AF) { // data has not been acknowledged
return I2C_MASTER_RC_NAK;
}
return I2C_MASTER_RC_NONE;
@ -417,12 +477,12 @@ enum i2c_master_rc i2c_master_address_write(uint16_t slave, bool address_10bit,
}
}
rc = i2c_master_stop(); // sent stop condition
if (I2C_MASTER_RC_NONE != rc) {
goto error;
}
rc = I2C_MASTER_RC_NONE; // all went fine
error:
if (I2C_MASTER_RC_NONE != rc) {
i2c_master_stop();
} else {
rc = i2c_master_stop(); // sent stop condition
}
return rc;
}

4
i2c_master.h
View File

@ -21,10 +21,10 @@ enum i2c_master_rc {
};
/** setup I²C peripheral
* @param[in] fast if Standard mode (Sm) is used for frequencies at 100 kHz, and Fast mode (Fm) is used for frequencies at 320 kHz
* @param[in] freq_khz desired clock frequency, in kHz
* @return if I²C bus is ready to be used (same as i2c_master_check_signals)
*/
bool i2c_master_setup(bool fast);
bool i2c_master_setup(uint16_t freq_khz);
/** release I²C peripheral */
void i2c_master_release(void);
/** reset I²C peripheral, fixing any locked state