STM32nucleo development board, mcu is STM32L053R8, LPUART uses external 32.768kHz crystal oscillator (LSE), baud rate 9600. In STOP mode, the error rate of the first byte of received data is very high (30%~40%). For example, the PC sends a character string "sleep" (73 6C 65 65 70 0D 0A), and the MCU receives "髄eep" ((F3 6C 65 65 70 0D 0A). If the baud rate is changed to 4800, there will be no Question. What is the reason for this and is there any way to solve it?
Mana Posted on January 29, 2021
See how big the crystal frequency is selected in stop mode. Generally speaking, sleep will reduce the speed, which will affect the baud rate.
Suzy Posted on January 29, 2021
It should be caused by the crystal frequency error.
The 32.768kHz crystal frequency division 9600 should be very accurate. It is estimated that the crystal oscillator you choose is not good.
Kevan Posted on January 29, 2021
The latter is right, the crystal frequency should be no problem, if the first few bytes are always wrong, you can try to delay
