All major components have arrived, including the ELM327, ATmega644P, and RN-41 bluetooth module. Shwetak provided a 3-axis accelerometer for us to use. (4/20/10)
Assembly of a prototype has been started on a breadboard. Still need to built a 3.3V power supply as of 4/21/10.
3.3V power supply is complete! Everything is wired up and should be ready to communicate except the memory module. (4/22/10)
Obtained list of data that needs to be collected from the car:
Store the following measures, at fixed time intervals, from the OBDII port (via the device)* the corresponding PIDs can be found online at a variety of sources including the following: http://en.wikipedia.org/wiki/OBD-II_PIDs
- VIN #
- Vehicle speed every second
- Engine speed (RPM) every second
- Air Flow Rate every second
- Coolant Temperature every second
- Short Term Fuel Trim (B1)
- Short Term Fuel Trim (B2)
- Long Term Fuel Trim (B1)
- Long Term Fuel Trim (B2)
- O2 Sensor Voltage (B1, S1)
- O2 Sensor Voltage (B1, S2)
- O2 Sensor Voltage (B2, S1)
- O2 Sensor Voltage (B2, S2)
- Intake Manifold Pressure
- Intake Air Temp.
- Fuel Pressure
- Engine Load
The bluetooth module is able to transmit data from the microcontroller to a bluetooth enabled computer. It also is able to receive data from the computer. It was discovered that the 1MHz clock within our microcontroller has trouble with placing a higher baud rate for the bluetooth module. According to the data sheet, 38400 bps should work just fine. However, it wasn't until the baud rate was lowered to 9600 bps that the data made it through. This will limit us to transmitting 1 Kbyte of data per second unless we place an external clock on the microcontroller. Our Elm chip uses a baud rate of 38400. This error might only effect bluetooth communications, but we should make sure that communication with the elm chip is possible at this rate.
Changed ELM baud rate to 9600 for testing. I have not been able to get communication working. The OBD connector has arrived and the CAN and ISO pins (along with power and the power conversion circuitry) have been wired up. Installed and started playing around with the simulator software. I still need to wire up the memory, but I figure that can wait until we can get information from the ELM. I need to look through the datasheet a little further to make sure all of the settings are correct. -Ben (4/24/10)