MoTeC Global Forum

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

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.

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

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.