On Fri, 6 Jul 2012 15:41:32 -0500 (CDT), you wrote: >On Fri, July 6, 2012 3:15 pm, John Hansen wrote: >> I have been trying to decipher a communications protocol for some time n= ow >> with only limited success. It is used for communicating data between a >> microphone and the body of a radio transceiver (Kenwood D710 for amateur >> radio). All communication occurs on a single wire; there are not separat= e >> data and clock lines. In terms of the operation of the radio, there >> really >> isn't any need for bi-directional communication... data only needs to fl= ow >> from the microphone to the radio. >> >> I created a webpage that has the oscilloscope screen shots for the data >> captured flowing between the microphone and the radio. I have found how >> the data is encoded, but what I haven't been able to decipher is the >> handshaking that seems to be occurring between the two. >> >> If you have the time and inclination to take a look at this, I would >> appreciate any suggestions that you might have. Someone told me that th= ey >> have seen this before, but they are either unwilling or unable to tell m= e >> where or what it's called. They also suggested that a PIC lacked the >> horsepower needed to communicate using this protocol, but based on what >> I'm >> seeing on the scope, this seems to me to be very unlikely. >> >> The web page with the details is at: www.johnhansen.org >> >> Thanks in advance for any ideas! > >I have not seen this protocol before, but this sure seems like a good >application for the "logic" analyzer: This >has the combination of very deep memory and fast enough sampling so you >should be able to record and decode the protocol. I can loan you mine for >a short time if you're in the area (near Austin, TX), but the logic is >relatively cheap- just buy one! > >(just a happy user of the logic) > > > A very handy trick when looking at 1-wire protocols is to add some series r= esistance to the line (and pullups if it isn't open-drain) , so you can tell from slight differen= ces in voltage levels which end is talking at any time.=20 If things get really complex, you should be able to tweak the resistance, p= ullups and analyzer input thresholds in such a way that you can get a clean, seperate signal fo= r transmissions at each end.=20 Being able to tell who is talking when can go a long way to figuring out ha= ndshakes, acknowledges etc. over a 1-wire bus --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .