how to use MB for transmit in FlexCAN when RXFIFO is active?

[Ahmad_bozorgi]

Hi.

in s32k1xx, we deal with 32 MB that can be used for receive or transmit. when we want to use RXFIFO, we can set the "Message buffers occupied by Rx FIFO and ID filter table" with CTRL2[RFFN] field. 

A. let assume we set "RFFN[3:0] = 0x9", so MB 0-25 will be used as RX FIFO & ID filter. remained MB can use for TX buffer? we should use these buffers for transmit data?

B. if we use maximum MB (which is 32) for RX FIFO & ID filter, how we should use MB for transmit?

C. for implementation TTCAN, should be there any hardware or it can be done by software? if YES, anybody has sample code form NXP?

Thsnks.

[enwei]

Hi，

For your questions,

1. if Remaining Available Mailboxes is not zero after RxFIFO enabled, you can use them as individaul MB for CAN 2.0 A/B message frame transmit or received( RxFIFO does not support CAN-FD on S32K1xx FlexCAN). For example code, you can refer to  S32K144_CAN_PAL_SamplePrj_Basic_TxRx_ID_FiltersConfig_SDKRTM3P0 from below link:

https://community.nxp.com/t5/S32K-Knowledge-Base/S32K1xx-SDK-FlexCAN-sample-projects-to-demonstrate-...

2. if all MB are configured and used for RX FIFO & ID filter, no MB for transmit.

3. NO hardware TTCAN support feature on S32K1xx FlexCAN module, you should SW ti implement the TTCAN if needed,  but sorry for no TTCAN example avialable for your reference.

Best Regard,

Enwei Hu.