topic Re: How to set LPC5516 CANFD sample point to more than 70% when baudrate more than 4M? in LPC Microcontrollers

How to set LPC5516 CANFD sample point to more than 70% when baudrate more than 4M?

wangyanjun — Sun, 14 May 2023 10:16:46 GMT

When set sample point more than 70%, there will be a Protocol error in data phase and an error frame will be transmitted. No such problem when data baudrate less than 4M.Sample point less than 70% works well.

MCU: LPC5516

CANFD transmitter: TJA1042/3

CANFD module clock: 80MHz

Comm interface: Kvaser Hybrid

BTW: LPC54616 with same configuration works well.

Re: How to set LPC5516 CANFD sample point to more than 70% when baudrate more than 4M?

xiangjun_rong — Mon, 15 May 2023 03:19:03 GMT

Hi,

For your application, you set the CAN baud rate as 4M, I suppose that it is a bit high.

For the CAN bit sampling point, it is complicated to select the sampling point,.

I attach the an1798.pdf, hope it can help you

XiangJun Rong

Re: How to set LPC5516 CANFD sample point to more than 70% when baudrate more than 4M?

wangyanjun — Mon, 15 May 2023 03:58:40 GMT

I use CAN FD, and data phase baudrate set to 4M, nominal baudrate set to 1M.

As SAE J2284-5, CAN FD baudrate can be set to 500K/5M.

In my application, when set to 500K/5M, sample point more than 75%, it can transmit and receive messages, but there are some error frames generated.

I want to confirm:

Is the LPC5516 support sample point >= 75%?

Re: How to set LPC5516 CANFD sample point to more than 70% when baudrate more than 4M?

xiangjun_rong — Wed, 17 May 2023 02:27:09 GMT

Hi,

Regarding your question, the sampling point of CAN receiver is dependent on the the cable length, the signal quality..., I suppose it is okay to set the sampling point more than 75%.

Hope it can help you

XiangJun Rong

Re: How to set LPC5516 CANFD sample point to more than 70% when baudrate more than 4M?

frank_m — Wed, 17 May 2023 10:23:21 GMT

> Regarding your question, the sampling point of CAN receiver is dependent on the the cable length, the signal quality...,

And proper termination.
The higher the baudrate, the more critical it becomes.
The bandwidth requirements are at least an order of magnitude higher than the nominal baudrate.