USART1_IRQHandler ISR routine not been called?

Enable ISR routine? What is this - enable NVIC or UART interrupts? Both are needed. Do you use ST's HAL or LL library or something home rolled?

-- pa

I believe I did both. See below. Thx

In startup_stm32f407xx.s -

 .word   USART1_IRQHandler         /* USART1            */          

 .word   USART2_IRQHandler         /* USART2            */          

 .word   USART3_IRQHandler         /* USART3            */ 

In uart.c -

  /* USART1 interrupt Init */

  HAL_NVIC_SetPriority(USART1_IRQn, 0, 0);

  HAL_NVIC_EnableIRQ(USART1_IRQn);

do you use the cube ?

I had to enable the DMA and the Uart interrupt,

please check my posts, here:

https://community.st.com/s/question/0D50X00009sVTZFSA4/haluartreceivedma-calls-rxcpltcallback-but-receives-no-data

Check for framing, parity and noise type errors, and clear them.

Could just be it's not receiving anything properly. RX not enabled, wrong pin, noisy signals, inversion.

If you use HAL_UART_Receive_IT or HAL_UART_Transmit_IT - these functions enable needed UART interrupts (*), so you're done. Check other reasons why interrupt does not arrive. Functions without _IT in their name simply do not use interrupts, if you use these functions, it is normal that no UART interrupts occur.

-- pa

(*) for example: https://github.com/pavel-a/stm32f4_libs/blob/c4560650ddaea6ee33de171027d801a31109565a/STM32Cube_FW_F4/Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_usart.c#L736

I do get into USART1_IRQHandler() for TX just not for RX when I have input from teraterm through Prolific USB to serial Comm port. Thx

Kind of hard to debug with no code, no schematic, and no scope traces.

Make sure the status register isn't flagging errors, that the interrupt for RXNE is enabled. Check peripheral registers in debugger. Check wiring and pin numbers. Probe signal at pin.

Got it now, need enable RX interrupt in CR1. Thx

 // RXNE Interrupt Enable

 SET_BIT(huart1.Instance->CR1, USART_CR1_RXNEIE);