MCAN of LPC5516 cannot filter IDs

[1318614689]

I configured MCAN's extended ID filter as shown below

I thought MCAN would receive frames with IDs 60 to 65 and reject others,But MCAN sends ACK for IDs outside the filter range。

Is there a way to make MCAN not send ACKs to IDs outside the filter range?

[xiangjun_rong]

Hi,

For the CAN reception Filter data format of LPC551x, pls refer to the section 41.12 Standard message ID filter element in UM11295.pdf

Both the SFEC bits and SFT bits define the Filter feature. For example, If the SFT=0x0, range filter is used.

Hope it can help you

BR

XiangJun Rong

[frank_m · Accepted solution]

I think you need to study the CAN/filter section for the LPC55xx. While I don't know that specific MCU, this is not how other MCUs and CAN filter settings work.

You settings contradict each other. When rejecting IDs 0 to 7FF, there will be nothing left to process.

But more important, these filters do not stop the CAN peripheral from receiving such frames on the bus, nor do they stop it from acknowledging frames. This is a CAN bus requirement.

The filter settings only affect what messages will be copied to the internal message buffer(s) and create interrupts. In other words, the core only notices those messages you set to accept.