Posted on September 08, 2015 at 12:27According to STM32F3 Reference Manual RM0316 and accelerometer/magnetometer LSM303DLHC Datasheet both these devices support I2C fast-mode at 400kHz, yet when I measure the GPIO PB6 with my oscilloscope, I only get about 82kHz.
We run the system clock from HSE (8 MHz) multiplied by 9 to 72 MHz.
When I specify to use the HSI at 8 MHz
I downloaded the stsw-stm32126 Excel sheet configuration tool to get the value for the `TIMINGR`register correct (also using Application Note AN4235), but no improvements can be detected. I use no filters and the fall/rise times are set to 300ns in the excel sheet.
If I use the HSI clock which only runs at 8 MHz, I get faster performance than with the SYSCLK.
RCC_PeriphClkInit.I2c1ClockSelection = RCC_I2C1CLKSOURCE_HSI or _SYSCLK;
Is there something I have completely missed or is this not supposed to work?
#i2c #lsm303dlhc #stm32f3
