Sending CAN data to PDM

[Martin]

Hi,

I would like to send Lateral Gforce to the PDM from an M800 via CAN

How would negative G`s be seen on the PDM?


Thanks
Martin

[DarrenR]

Hi Martin,

Unfortualtly the PDM is a simple device and doesn't deal with negitive numbers. You need to offset the calibration of the G sensor in the ECU. So for example, in the G force custom calibration, set 10 for 0G, 5 for -5G and 15 for +5G. Recieve the value in the PDM as 16bit and set a divisor of 100. In the PDM this will give you a value of 100 for 0G, 50 for -5G and 150 for +5G.
if you need better resolution than 0.1G you can divide by say 10 to give 0.01G resolution but you will have to calibrate the G sensor in ECU manager with an offset of 1.28G. This would give a range of -1.28G (value of 0) to + 1.27G (value of 255) 0G would have a value of 128 in the PDM.

Since the G force logged value will have an offset, just minus the offset away in i2 to make it back to the correct numbers. I know it is not ideal so we are looking to make improvements in this area.

If sending the G force from a dash, the channel values in the dash can remain correct but the values in the PDM still come out the same.

[Martin]

Thanks for your prompt reply


Ive got it...Ill just keep the G force channel original in the Dash and also log it there. Ill offset the Gforce channel in the ECU when it receves G force over CAN and then transmit the offset channel to the PDM.

One more thing...
If the ECU sends 4 channels on HEX 118 (dec 280) on a custom template....does this mean that HEX 119(dec 281) is not occupied and that i can set up an ADL template to send data on 119 (281) to the PDM?


Cheers
Martin

[DarrenR]

Yes sure that is fine.
However if you were to add one more item to the custom data set in the M800 then the ECU would also transmit a message on 0x119 which causes problems.

I would suggest to transmit on address 0x11A from the dash, rather than 0x119, which leaves room for up to 8 channels sent from the M800 if you want to add more down the track.