topic LPC55S16 - UART Framing Error - How To Recover? in LPC Microcontrollers

LPC55S16 - UART Framing Error - How To Recover?

JK_265 — Thu, 31 Oct 2024 16:30:40 GMT

Using an LPC55S16 to communicate via UART. Unfortunately, the system has some noise, and the RX line is occasionally pulled low momentarily, which the UART interprets as a start bit. This ultimately leads to a framing error.

What is the suggested methodology for recovering from a framing error? I'd was thinking just vector on a framing error, reset some flags, and throw out the byte. But this is just a high level concept. Can I please get a detailed description of what should be done in this situation?

Thanks!

Re: LPC55S16 - UART Framing Error - How To Recover?

Harry_Zhang — Fri, 01 Nov 2024 09:04:47 GMT

Hi @JK_265

I think you can refer to lpc55s16_usart_interrupt example.

But you need change some code.

USART_EnableInterrupts(DEMO_USART, kUSART_RxLevelInterruptEnable | kUSART_RxErrorInterruptEnable);

change to

USART_EnableInterrupts(DEMO_USART, kUSART_RxLevelInterruptEnable | kUSART_RxErrorInterruptEnable | kUSART_FramingErrorInterruptEnable);

And you also need to change DEMO_USART_IRQHandler function.

void DEMO_USART_IRQHandler(void) { uint8_t data; /* If new data arrived. */ if ((kUSART_RxFifoNotEmptyFlag | kUSART_RxError) & USART_GetStatusFlags(DEMO_USART)) { data = USART_ReadByte(DEMO_USART); /* If ring buffer is not full, add data to ring buffer. */ if (((rxIndex + 1) % DEMO_RING_BUFFER_SIZE) != txIndex) { demoRingBuffer[rxIndex] = data; rxIndex++; rxIndex %= DEMO_RING_BUFFER_SIZE; } } if (kUSART_FramingErrorInterruptEnable & USART_GetStatusFlags(DEMO_USART)) { uint8_t discard = USART_ReadByte(DEMO_USART); errorCounter++; } SDK_ISR_EXIT_BARRIER; }

Hang

Re: LPC55S16 - UART Framing Error - How To Recover?

JK_265 — Fri, 15 Nov 2024 21:56:26 GMT

@Harry_Zhang I am currently working in a polling mode where this issue occurs when using USART_READBlocking( which returns 0x5711, framing error). What to do in this situation? Thanks.

Re: LPC55S16 - UART Framing Error - How To Recover?

Harry_Zhang — Fri, 29 Nov 2024 02:00:32 GMT

Hi @JK_265

This means that the received frame is incorrect.

I suggest you use this example to automatically discard frames when they are received incorrectly, and receive frames when they are received correctly.

Harry