Doubt with LPC1752 CAN peripheral interface

[gaoqiang]

I recently got a board of LPC1752FBD80. I checked the circuit diagram. The CAN transceiver used is TJA1040. The TXD and RXD of the transceiver are connected to The pin P2[0] and P2[1]. Checked the datasheet of LPC1752, the two pin multiplexing functions are TXD1 and RXD1 of the serial USART1, not the designated pins of the CAN peripheral;
I want to know how to config to achieve the CAN communication function of P2[0] and P2[1], thank you very much!

[soledad]

Hi, 

In my opinion, there is something wrong with the schematic file. The CAN-controller of the microcontroller should be connected to the transceiver via TXD and RXD. Pin STB is connected to an I/O pin of the host microcontroller for operation mode control. For this MCU the pins should be P0.0 and P0.1 according to the reference manual. 

Please check the following example circuit diagram. 

I hope this helps, have a nice day!

Regards

Soledad

[gaoqiang]

Today, when I checked the reference manual of the LPC1752, I found that the UART1 has this feature: RS-485 support. Is it use the 485 function of the UART1 through the TJA1040?

have a nice day!

Regards

gao

[soledad]

Hi, 

Unfortunately, I cannot determinate why these pins are connected to P2[0] and P2[1]. 

Please check the AN10211 application note, this appnote presents a typical application example for the TJA1040 and application hints dealing with the split termination concept and required external circuitry.

 https://www.nxp.com/docs/en/application-note/AN10211.pdf 

You can use it as a reference. 

Have a nice day!

Regards

Sol 

[gaoqiang]

Thank you very much for your reply!
This board is at my fingertips. I have confirmed it several times, but he did connect P2.0 and P2.1 to TJA1040's TXD and RXD. I am also very confused, his P0.0 and P0.1 connected to another CAN communication chip. Is the engineer who designed this circuit use ordinary IO port to simulate CAN communication? In that case, it is too difficult.

have a nice day!

Regards

gao