[I2C] Timing can be hard coded

To avoid time spent to compute the I2C timing, it can be defined in the variant.h or build_opt.h or hal_conf_extra.h with: * I2C_TIMING_SM for Standard Mode (100kHz) * I2C_TIMING_FM for Fast Mode (400kHz) * I2C_TIMING_FMP for Fast Mode Plus (1000kHz) Example for a STM32F0xx using HSI clock as I2C clock source: #define I2C_TIMING_SM 0x00201D2B #define I2C_TIMING_FM 0x0010020A Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: fpistm

cores/arduino/stm32/twi.c

@@ -476,13 +476,25 @@ static uint32_t i2c_getTiming(i2c_t *obj, uint32_t frequency)
  switch (i2c_speed) {
  default:
  case 100000:
+#ifdef I2C_TIMING_SM
+ ret = I2C_TIMING_SM;
+#else
  ret = i2c_computeTiming(i2c_getClkFreq(obj->i2c), I2C_SPEED_FREQ_STANDARD);
+#endif
  break;
  case 400000:
+#ifdef I2C_TIMING_FM
+ ret = I2C_TIMING_FM;
+#else
  ret = i2c_computeTiming(i2c_getClkFreq(obj->i2c), I2C_SPEED_FREQ_FAST);
+#endif
  break;
  case 1000000:
+#ifdef I2C_TIMING_FMP
+ ret = I2C_TIMING_FMP;
+#else
  ret = i2c_computeTiming(i2c_getClkFreq(obj->i2c), I2C_SPEED_FREQ_FAST_PLUS);
+#endif
  break;
  }
  }

variants/board_template/variant.h

@@ -113,6 +113,14 @@ extern "C" {
 //#define PIN_WIRE_SDA 14 // Default for Arduino connector compatibility
 //#define PIN_WIRE_SCL 15 // Default for Arduino connector compatibility
 
+// I2C timing definitions (optional), avoid time spent to compute if defined
+// * I2C_TIMING_SM for Standard Mode (100kHz)
+// * I2C_TIMING_FM for Fast Mode (400kHz)
+// * I2C_TIMING_FMP for Fast Mode Plus (1000kHz)
+//#define I2C_TIMING_SM 0x00000000
+//#define I2C_TIMING_FM 0x00000000
+//#define I2C_TIMING_FMP 0x00000000
+
 // Timer Definitions (optional)
 //Do not use timer used by PWM pins when possible. See PinMap_PWM in PeripheralPins.c
 #define TIMER_TONE TIMx