What are the correct pins for ISP over CAN on the 5534?

[dlayne_i2]

Hi,

I am working on a project which requires performing software updates in the field via the CAN interface using a LPC5534 processor.  According to the documentation this should be supported.  However, there is an apparent contradiction as to what the correct pin assignments should be.  I am consulting the following two documents:

LPC553x Reference Manual, Rev. 4, 2024-11-21
LPC55S3x Product data sheet Rev. 5.0 — 7 March 2024

According to the data sheet:

So, the data sheet wants us to use PIO0_29 for RX and PIO0_30 for TX.

But, the manual says this:

So, the manual agrees on the TX pin, but wants us to use PIO1_22 for RX.

Which is correct?  I have been experimenting trying to get the chip into CAN ISP mode and communicating with blhost, but so far nothing has worked.

Thanks,
-David Layne

[luis_maravilla]

Hello,

The pin for CAN_RXD is PIO1_22;
In LPC553x Product data sheet Rev. 5.0 — 7 March 2024 table 3 page 43; description indicate that the PIO1_22 contains CAN0_RD, this confirms information with table 119 in Reference Manual.

Best Regards, Luis

[dlayne_i2]

Hi Luis, thanks for getting back to me.  While the data sheet does say what you quoted, the same language is also present for all of the following pins:

PIO1_3 function 1, page 32
PIO0_4 function 1, page 14

and PIO0_29 contains the remark about the pin being used specifically in ISP mode.

This makes me nervous as we are finalizing our schematic and it will be difficult to change pins if it turns out we cannot get ISP working over CAN on that pin.

[luis_maravilla]

Hello,

Above Table 119. ISP Assignments in Reference Manual, comment about that the descriptions show in table are the default pin assignment used by the ROM code that cannot be changed.

Could you help us confirm if using the PIO1_22 for CAN_RXD and maintaining PIO0_30 for CAN_TXD can communicate with blhost?

Please, let me know your findings.

Best Regards, Luis