S32K148: Frequent UART_FRAMING_ERROR

zitong_zhang — Fri, 26 Feb 2021 08:54:47 GMT

Dear all,

I am having some trouble with the UART module where UART_FRAMING_ERROR occurs very frequently that only 20% of the payload is received successfully.

The project uses freeRTOS and the S32 SDK. A task receives UART packets from another chip (iMX6). The UART packet starts with 0xAE and has a fixed length of 88 bytes (RX_BUFF_LEN). It is sent to S32K148 at 100Hz with a baud rate of 460800.

I have used similar tasks to receive data from other devices before, which worked fine. The code also works when I send data from a Raspberry Pi to an S32K148_EVB (same data format as memtioned above). But when switching to the actual project, LPUART_DRV_GetReceiveStatus frequently returns UART_FRAMING_ERROR (as sample from FreeMaster). As a result, only 20% of the payload is received: a counter increases upon successful reception, and FreeMaster shows this counter only increases by 20 each second, instead of the expected 100Hz.

To add a few points:

1. The S32K148 uses CLK_SRC_SPLL_DIV2 as the clock source, process expert shows an actual baudrate of 465116, which doesn't look ridiculous;

2. I have also tried reducing the baudrate to 115200 with no success;

3. The iMX6 chip seems to receive data from S32K148 OK, at least much more smoothly;

I have inserted part of the code below. I wonder if you could share your thoughts on this issue.

Many thanks!

Zitong

LPUART_DRV_ReceiveData(INST_LPUART1, &u8RxBuffer[0], RX_BUFF_LEN); for (;;) { /* poll rx status */ eRxStat = LPUART_DRV_GetReceiveStatus(INST_LPUART1, &u32BytesLeft); if ( eRxStat == STATUS_BUSY ) { /* if rx in progress */ u16BytesReceived = RX_BUFF_LEN - (uint16_t)u32BytesLeft; if ( u16BytesReceived > 0 ) { /* if at least one byte received */ if (0xAE != u8RxBuffer[0]) { /* if packet header missed */ /* abort current receive since the packet is incomplete */ LPUART_DRV_AbortReceivingData(INST_LPUART1); /* restart receive after 2ms so that the current packet is flushed */ vTaskDelay(2); LPUART_DRV_ReceiveData(INST_LPUART1, u8RxBuffer, RX_BUFF_LEN); } } } else if ( eRxStat == STATUS_SUCCESS ) { /* if transfer successful */ /* handle received data */ /* restart receive */ LPUART_DRV_ReceiveData(INST_LPUART1, u8RxBuffer, RX_BUFF_LEN); vTaskDelay(1); } else { /* if error occurs */ /* restarts receive */ LPUART_DRV_ReceiveData(INST_LPUART1, u8RxBuffer, RX_BUFF_LEN); } vTaskDelay(1); }

Re: S32K148: Frequent UART_FRAMING_ERROR

danielmartynek — Fri, 26 Feb 2021 14:27:20 GMT

Hello Zitong,

Since the Framing Error is reported when the received char has 0 where a stop bit should be,

I would double check the baudrate.

Can you please scope the signal both from the S32K148 and the iMX6?

Please have a look at Section 53.4.2 Baud rate generation in the RM, rev12.1

Depending on the over sampling ratio, the receiver has an acquisition rate of 4 to 32 samples per bit time.

Regards,

Daniel

Re: S32K148: Frequent UART_FRAMING_ERROR

iysheng — Sun, 23 Jun 2024 09:23:58 GMT

I meet similar problem like you, and I fixed this by set rx pin pull up enable.Maybe you can try this too.

Re: S32K148: Frequent UART_FRAMING_ERROR

toipaz — Wed, 12 Feb 2025 23:45:26 GMT

1. The S32K148 uses CLK_SRC_SPLL_DIV2 as the clock source, process expert shows an actual baudrate of 465116, which doesn't look ridiculous;

--> the actual baudrate for 460800 in S32K148 can be updated to 460905 by using SPLLDIV2 Clock 112MHz for LPUART clock.

For this,

1) SPL_VCO set [ / 1 * 28 ] and output 224 MHz

2) SPL CLOCK set [ / 2 ] and output 112 MHz

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