Going from OEM tires to 37" Ridge Grapplers, without a change in diff gearing requires a 12% bump. The laptop shows a before and after with the above filter in place. To trial I setup a second RPi 4b to listen to the second channel. The code is not optimal as filtering is done within the software but I can tweak that as I learn the python-can library some more. If not, the message is passed unaffected onto the second channel. If found, the correction is applied, the message reconfigured, and then sent onto the second channel. The premise is that the CPU filters all messages looking for the speed arbitration ID of 0x00B4. Cut into the bus at the cluster and sent that to the first channel. Got the interceptor working with the onboard RPi 4b and a dual channel CAN card. Pretty slow process compared to internal CAN between the ECUs The OBD2 sends a signal asking for the Speed and then has to wait for the ECU to read its request and reply with the value. (On-board diagnostics Parameter IDs) or PIDs are literally universal commands to send into the OBD2 port asking for a value (ex. Big difference between OBD2 protocol PIDs for diagnostic monitoring and actual addresses and locations of data on the CAN Bus. "PIDs 12 and 13 in real time." Be careful here. It runs very fast (about 33 updates per second) and very accurate.įor reference the instrument cluster, Speed, Tach, Coolant Temp, Trans Temp as well as almost all warnings, lights, ect are run on the CAN Bus. I have been reading the CAN Speed signal and using it to run a digital speedometer for months with no problems. I am in the middle of a several month long project building a digital dash display that runs off the CAN Bus signals. The Cluster reads in the CAN signal, translates it and moves the Speedometer needle accordingly. It reads the pulses from the wheel speed sensors, determines the Speed and Distance using math and sends these signals along the CAN Bus. The Speed signal and Trip/Odometer signal are both broadcast by the Stability Control/ABS ECU. MY question is if it is also correcting the Distance signal that increments the Trip and Odometer. The rest of the CAN network is still seeing the old incorrect signal. The HyperTech and Rough County "Inline" Calibrators read the incorrect CAN bus signal for speed, does a conversion factor (based on your inputted new tire size ect), and then sends the newly corrected speed CAN signal to the Instrument cluster.
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