i2c: increase the default clock strech timeout to 250msec.
This also redefines the timeout in FreeRTOS clock ticks, and implements a two stage wait: firstly spinning sampling frequently, and then falling back to a longer wait while sampling less frequently and yielding.
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2 changed files with 42 additions and 23 deletions
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@ -66,7 +66,7 @@ typedef struct i2c_bus_description
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bool started;
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bool flag;
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bool force;
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uint32_t clk_stretch;
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TickType_t clk_stretch;
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} i2c_bus_description_t;
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static i2c_bus_description_t i2c_bus[I2C_MAX_BUS];
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@ -183,7 +183,7 @@ int i2c_set_frequency_hz(uint8_t bus, uint32_t freq)
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return not_ok ? -EINVAL : 0;
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}
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void i2c_set_clock_stretch(uint8_t bus, uint32_t clk_stretch)
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void i2c_set_clock_stretch(uint8_t bus, TickType_t clk_stretch)
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{
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i2c_bus[bus].clk_stretch = clk_stretch;
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}
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@ -235,13 +235,46 @@ static inline void clear_sda(uint8_t bus)
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#endif
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}
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static inline void set_scl(uint8_t bus)
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#define I2C_CLK_STRETCH_SPIN 1024
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static void set_scl(uint8_t bus)
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{
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#if I2C_USE_GPIO16 == 1
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gpio_write(i2c_bus[bus].g_scl_pin, 1);
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#else
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GPIO.OUT_SET = i2c_bus[bus].g_scl_mask;
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#endif
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// Clock stretching.
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// Spin sampling frequently.
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uint32_t clk_stretch_spin = I2C_CLK_STRETCH_SPIN;
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do {
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if (read_scl(bus)) {
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return;
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}
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clk_stretch_spin--;
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} while (clk_stretch_spin);
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// Fall back to a longer wait, sampling less frequently.
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TickType_t clk_stretch = i2c_bus[bus].clk_stretch;
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TickType_t start = xTaskGetTickCount();
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do {
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vTaskDelay(20 / portTICK_PERIOD_MS);
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if (read_scl(bus)) {
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return;
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}
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TickType_t elapsed = xTaskGetTickCount() - start;
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if (elapsed > clk_stretch) {
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break;
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}
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} while (1);
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debug("bus %u clock stretch timeout", bus);
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}
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static inline void set_sda(uint8_t bus)
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@ -265,10 +298,7 @@ void i2c_start(uint8_t bus)
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// Set SDA to 1
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set_sda(bus);
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i2c_delay(bus);
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uint32_t clk_stretch = i2c_bus[bus].clk_stretch;
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set_scl(bus);
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while (read_scl(bus) == 0 && clk_stretch--)
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;
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// Repeated start setup time, minimum 4.7us
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i2c_delay(bus);
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}
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@ -286,14 +316,10 @@ void i2c_start(uint8_t bus)
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// Output stop condition
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bool i2c_stop(uint8_t bus)
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{
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uint32_t clk_stretch = i2c_bus[bus].clk_stretch;
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// Set SDA to 0
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clear_sda(bus);
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i2c_delay(bus);
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// Clock stretching
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set_scl(bus);
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while (read_scl(bus) == 0 && clk_stretch--)
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;
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// Stop bit setup time, minimum 4us
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i2c_delay(bus);
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// SCL is high, set SDA from 0 to 1
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@ -315,17 +341,13 @@ bool i2c_stop(uint8_t bus)
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// Write a bit to I2C bus
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static void i2c_write_bit(uint8_t bus, bool bit)
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{
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uint32_t clk_stretch = i2c_bus[bus].clk_stretch;
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if (bit) {
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set_sda(bus);
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} else {
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clear_sda(bus);
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}
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i2c_delay(bus);
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// Clock stretching
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set_scl(bus);
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while (read_scl(bus) == 0 && clk_stretch--)
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;
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// SCL is high, now data is valid
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// If SDA is high, check that nobody else is driving SDA
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if (bit && read_sda(bus) == 0) {
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@ -338,15 +360,11 @@ static void i2c_write_bit(uint8_t bus, bool bit)
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// Read a bit from I2C bus
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static bool i2c_read_bit(uint8_t bus)
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{
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uint32_t clk_stretch = i2c_bus[bus].clk_stretch;
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bool bit;
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// Let the slave drive data
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set_sda(bus);
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i2c_delay(bus);
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set_scl(bus);
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// Clock stretching
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while (read_scl(bus) == 0 && clk_stretch--)
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;
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// SCL is high, now data is valid
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bit = read_sda(bus);
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i2c_delay(bus);
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@ -32,6 +32,8 @@
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#include <stdint.h>
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#include <stdbool.h>
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#include <errno.h>
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#include <FreeRTOS.h>
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#include <task.h>
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#ifdef __cplusplus
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extern "C" {
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@ -51,7 +53,8 @@ extern "C" {
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#define I2C_USE_GPIO16 0
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#endif
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#define I2C_DEFAULT_CLK_STRETCH (10)
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/* Default clock strech waiting time, 250 msec. */
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#define I2C_DEFAULT_CLK_STRETCH (250 / portTICK_PERIOD_MS)
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/* SCL speed settings. 160 MHz sysclk frequency will result in improved
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* timing accuracy. Greater bitrates will have poorer accuracy. 1000K is the
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@ -86,7 +89,6 @@ typedef struct i2c_dev
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* @param scl_pin SCL pin for I2C
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* @param sda_pin SDA pin for I2C
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* @param freq frequency of bus (ex : I2C_FREQ_400K)
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* @param clk_stretch I2C clock stretch. I2C_DEFAULT_CLK_STRETCH would be good in most cases
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* @return Non-zero if error occured
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*/
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int i2c_init(uint8_t bus, uint8_t scl_pin, uint8_t sda_pin, i2c_freq_t freq);
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@ -97,7 +99,6 @@ int i2c_init(uint8_t bus, uint8_t scl_pin, uint8_t sda_pin, i2c_freq_t freq);
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* @param scl_pin SCL pin for I2C
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* @param sda_pin SDA pin for I2C
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* @param freq frequency of bus in hertz
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* @param clk_stretch I2C clock stretch. I2C_DEFAULT_CLK_STRETCH would be good in most cases
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* @return Non-zero if error occured
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*/
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int i2c_init_hz(uint8_t bus, uint8_t scl_pin, uint8_t sda_pin, uint32_t freq);
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@ -119,9 +120,9 @@ int i2c_set_frequency_hz(uint8_t bus, uint32_t freq);
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/**
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* Change clock stretch
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* @param bus I2C bus
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* @param clk_stretch I2C clock stretch. I2C_DEFAULT_CLK_STRETCH by default
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* @param clk_stretch I2C clock stretch, in ticks. I2C_DEFAULT_CLK_STRETCH by default
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*/
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void i2c_set_clock_stretch(uint8_t bus, uint32_t clk_stretch);
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void i2c_set_clock_stretch(uint8_t bus, TickType_t clk_stretch);
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/**
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* Write a byte to I2C bus.
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