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Nucleo 32 - Unable to reach high baud rates

Question asked by Florian Knorr on May 27, 2018
Latest reply on May 27, 2018 by Florian Knorr



i am using a Nucleo 32 board with STM32L432KC chipset. I need to transfer data from a mems microphone over USB to the pc continuously. To do this i need a baud rate with at least 1.5Mbaud. The MCU is supporting baud rates up to 10Mbit, so it should be possible. On the pc side i am measuring the data rate. E. g. at 9200 Baud i get 920 Bytes per second (approx.) and this is true for higher baud rate till to some point where the number of bytes per sec. i receive is not increasing anymore.


42700 Bytes / sec. is the maximum i can reach. Why?


I used different cables, different USB ports, different Operating Systems and different software to measure the speed. Same result every time.


To communicate with the PC i have go talk with the onboard debugger chip that is connect via USB. I don't know what this chip is doing during communication and if it is the bottleneck.


Code is very simple:


uint8_t* text = (uint8_t*)"012345678\n"; //This can be much bigger
while (1)
    HAL_UART_Transmit(&huart2, text, strlen((char*)text), 0xffff);



Does anyone know what i am doing wrong?

Can someone maybe provide an example that is working with higher transfer rates?

Do i have to build my on circuit to get rid of path over the debugger chip?