Cannot read CAN_FD frames through python API

[CANuser76]

Hello,

I have issues using PCANbasic API for CAN_FD for Python (I don't have any issues for normal CAN).
First of all, I don't have any issues through PCAN View, I can read and write CAN_FD frames.
But through my python script, I can send frames but when I try to read frames it doesn't work. I just receive three time a frame with these information :
ID = 1, DLC = 4, DATA = 0 (which looks like a status message)
After that, I receive a 0x20 status (empty queue).
Whereas, I should receive many frames every 100ms with different ID, not empty datas and DLC = 16.

Here's the configuration that work with PCAN view :

Code: Select all

Clock = 80MHz

Nominal : 
BR = 1M/s
Sample point = 87.5%
Prescaler = 1
TSEG1 = 69
TSEG2 = 10
SJW = 10
tqs = 12.5ns
Nq = 80

DATA: 

BR = 5M/s
Sample point = 87.5%
Prescaler = 1
TSEG1 = 13
TSEG2 = 2
SJW = 2
tqs = 12.5ns
Nq = 16

Here's the configuration used in the API :

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b"f_clock_mhz=80, nom_brp=1, nom_tseg1=69, nom_tseg2=10, nom_sjw=10, nom_sam=87.5, data_brp=5, data_tseg1=13, data_tseg2=2, data_sjw=2, data_ssp_offset=87.5"

I think the problem is coming from nom_sam and data_ssp_offset as it's not totaly the same thing but I tried with different value and it didn't work.
When I read my configuration all the parameters are good except nom_sam which is =1 and data_ssp_offset which is = 0.
Could you help me please.
Have a great day !

[K.Wagner]

Hello,

Here's the configuration used in the API :
b"f_clock_mhz=80, nom_brp=1, nom_tseg1=69, nom_tseg2=10, nom_sjw=10, nom_sam=87.5, data_brp=5, data_tseg1=13, data_tseg2=2, data_sjw=2, data_ssp_offset=87.5"
I think the problem is coming from nom_sam and data_ssp_offset as it's not totaly the same thing but I tried with different value and it didn't work.

The bit rate string parameter you posted represents 1MB nominal and 1 MB data (not 5 MB) - it also contains unknown/not_used values that are just ignored. If you connect two nodes with a different bit rate for the data phase and you send messages with bit rate switch, your bus will probably go bus-off, so you will receive nothing but error frames (if configuried to get them). A correct bit rate string for 1MB/5MB with 87,5% sample point for both nominal and data phase, will be:

Code: Select all

f_clock=80000000,nom_brp=1,nom_tseg1=69,nom_tseg2=10,nom_sjw=10,data_brp=1,data_tseg1=13,data_tseg2=2,data_sjw=2

For the furtue, if you want to get a correct bit rate string value, you can do this in two easy ways:

1. Connect the PCAN-View to the bit rate that works for you, and then copy the bit rate configuration to the clipboard. Then use that values within your PCAN-Basic connection (* see pitcutre bellow).
2. Use our Bit rate Calculation tool, that can be downloaded here.