The DCI does read the voltage on the dash switch wire, but the voltage comes from the DCI, or in the case of the stock HU, from the HU.

The dash switch circuit puts various resistors to ground. Without the DCI or stock HU to provide the voltage, you won't read any voltage.

Try setting the meter to read resistance, put one meter lead on ground and the other on the dash switch wire and see what you get. You should see a different resistance for each dash switch pressed.

 

Here's the diagram of the S2000 dash controls. Inside the stock HU (or the DCI) is a 1k resistor from the output of the circuit to +5v.

 

Thanks! I'll go and check that, but I'm sure it will be correct since it works with the stock HU. I couldn't find that diagram in my search and was under the impression from others in general chat that the voltage was supplied by the vehicle, not head unit, to the resistor ladder network. At least I know that my car is working properly.

For the record, I should know better and am getting my own copy of the service manual, I thought I was going to have to wait for my manual to arrive to answer this one

I almost feel bad getting help from you Modifry, since the reason I was asking this is that I've ported some code from an IR communication robot I made last year to a new uC I'm playing with to mimic the stock dash button functionality as well and I wanted to get real values as input for my simulations.

Thanks again,
Mike

 

Why buy one? I think there is one posted on here somewhere....cant remember which forum, though.

John

 

One of my friends has the manual on CD and was just going to mail me a copy. I didn't realize this sort of thing could be posted freely... but I will now search and save on postage.

Thanks.

 

Oddly enough the schematic is in the Electrical Troubleshooting manual but with no resistor values. The values of the resistors are in the Mechanical service manual, but no schematic. Go figure.

As for doing your own thing, if you're smart enough to build uC circuit to control a HU then telling you how the resistors work ain't exactly giving away the store.

 

Well I do appreciate saving me the time of diagnosing my incorrect assumption. I placed a 1K resistor across the uC power and dash wire pins and everything works perfect, well almost too perfect. I need to delay after transmitting a code since there is only a few cycle delay from a change in voltage until the IR code start sequence begins and I use that time to put the actual code bit timings in queue so that there is not a wasted cycle. The joys of assembly. Anyway, I need to slow it down.

I've also used the mute button to multiplex the button combinations so that I can have more options when mute is enabled. I still have 3 of 8 I/O pins open for something and almost 70% of the code space left, but I haven't thought of anything else I want to do. For now I may try and migrate to all surface mount to try and get the board area to 100mm^2 2 layer from 400mm^2 1 layer as it is now. That, and remove the almost completely unneccessary optoisolation chip I used just because on the mute wire

Mike

 

They can not be posted freely as they violate Honda's copyright.

Also, I find it to be very bad form to ask for help from someone as to how their unit works when you're attempting to build a competing product. But what the hell do I know