I’m interfacing an ESP8266 with an NUCLEO-L073RZ using UART1 `PA9`, `PA10` for communication with the ESP and UART2 for communication with a PC for debugging. I also used a CP2102 USB to TTL converter to tap the Tx signal from UART1 and monitor AT commands sent from the STM32

The STM32 sends the first AT command correctly, but when I send the second command `AT+RST`, only part of it is received by the ESP8266. After debugging, I found that `HAL_UART_Transmit` returns `HAL_ERROR`, and the cause seems to be an overrun error.
See how I set things up:

_Baud rate : 115200 for both STM32 and ESP8266

_Buffer size: 256 bytes

_Communication method: Polling for UART communication

_Power supply: 5V regulated power source for ESP8266

Using `HAL_MAX_DELAY` as the timeout fixed the issue, but I’m unsure why. Increasing the delay in `HAL_Delay()` didn’t resolve the issue, so I’m still confused about what’s causing the overrun error.

Here’s the code I’m using to send AT commands;