I want to write my own software to log data using the CAN network on my 2007 Ford F150. I have bought a CANUSB and I managed to get one of the programs that comes with it to display some "random" data that are being transmitted on the network. However, when I send a request for specific data I get nothing back or it seems I am getting nothing back.
From the reading that I have done it seems that I need to send a normal CAN frame with 7DF in the address field and the mode(SID) and PID in the data field. Is this the case or am I missing anything.
Is there some sort of special initialization sequence that I need to follow in order to access the diagnostic functionality?