topic Re: LPC55S16 USART erroneous at 921600 baud rate in LPC Microcontrollers

LPC55S16 USART erroneous at 921600 baud rate

NaveenGS — Wed, 05 Apr 2023 11:30:43 GMT

Hi,

We are using LPC55S16 microcontroller running at 150MHz and using it to communicate with our sensor via USART(12MHz clock source) and is working good at the supported baud rates till 460800.
Does it really supports 921600 baud rate? We are able to get data at that rate but it seems under sampled and erroneous and CRC of the data always fails here.

As per UM11295.pdf, page no. 227(Also attached screenshot) we are missing 921600 baud rate in the supported list. Is it true?

Thank You,
Naveen G S

Re: LPC55S16 USART erroneous at 921600 baud rate

kef2 — Wed, 05 Apr 2023 12:16:41 GMT

Your screenshot is about UART ISP.

Look in 34,6,6

A 16-bit value allows producing standard baud rates from 300 baud and lower at the
highest frequency of the device, up to 921,600 baud from a base clock as low as 14.7456
MHz
Typically, the baud rate clock is 16 times the actual baud rate.

921600 * 16 =14,7456MHz, not 12MHz

Re: LPC55S16 USART erroneous at 921600 baud rate

NaveenGS — Wed, 05 Apr 2023 14:13:17 GMT

Hi,

Thank you for your response.

As per driver, if srcClk is 12Mhz and Baud rate expected is 921600 it should return kStatus_USART_BaudrateNotSupport. Isn't it? Is these kind of errors not handled in the driver?(Even in peripheral configurations, at least we expect it to raise minimal warning).

Thank You,

Naveen G S

Re: LPC55S16 USART erroneous at 921600 baud rate

xiangjun_rong — Thu, 06 Apr 2023 05:36:35 GMT

Hi,

Regarding the baudrate of usart, I suppose that you use traditional uart protocol, in other words, you connect TX, RX and GND between LPC55S16 USART and host USART, whether you can communicate between two USART reliably is only dependent on the the match degree of the driving clock of two USART modules, give an extreme example, if the two USART module(one is transmitter, another is receiver) use the same driving clock, in other words, the two USART module driving clock is 100% match, you can get very high baud rate.

Hope it can help you

XiangJun Rong