The right side of my (2011 level II) steering wheel has five buttons: Trip, Dist, air recirc, temp +/-. All but Trip and Dist are duplicates of nice big buttons on the climate console, so are rather redundant. I was hoping to repurpose those buttons for BT phone control etc. But according to Metra tech support, the Prius right-side steering wheel buttons are on a completely different interface bus and are invisible to the Metra. Can anyone confirm this? Quite sad if true. I may have to purchase a Head Unit with sufficient physical buttons so I can repurpose my left-side buttons as needed
I'd imagine to change their function, you'd have to undertake a serious rewiring project - not worth it.
All the steering wheel buttons work by switching resistors, so the only way to change the function is to either rewire all the resistors, or insert a ucontroller in the two wires (the buttons are divided into two sections) and convert the apparent resistance from each button to a new value (this is pretty much what the after market steering wheel interface units do).
Per the electric section of the shop manual, there is a resister network attached to the right hand switches that is connected to the AC amplifier (the AC display is part of that). So much for Metra and their bus. There is a microprocessor that supplies power to the resistor network and it is connected to the combination meter assembly CPU. I suspect the CPU connection is to light up the display that shows which button you pressed. A knowledgeable person could probably figure out how to make a standard adapter read the resistor network resistance on the wire that now goes to the AC amplifier and do something else with that information. The problem is getting both resistor networks (the radio control and the AC controls) read and fed into your radio. Jeremy Harris might know how practical that is.
It's possible to do it, but you'd need to be happy with writing code for a simple ucontroller and wiring some hardware to do it. I've only looked at one after market steering wheel adapter, and that had a ucontroller that was permanently coded, so couldn't easily be hacked. Not hard to do, but not something I'd want to try unless I was really desperate to get the buttons doing different things. BTW, the second connection to the buttons is the "touch tracer" system, the thing that lights up the panel when you brush a finger over the buttons. It would also need to be modded if you wanted to change the function of the buttons, else it would display the wrong thing up on the panel (it's independent from the resistor network that sends the button commands).
Not worth it. I happen to be familiar with embedded systems, microcode, etc... but why bother At this point, I simply want to find out if aftermarket HU's (particularly the Sony at this point) can understand BT Phone commands from a reconfigured steering wheel. I've not seen any documentation yet of what the various HU's understand. Doesn't appear to be part of either install guides or user guides, nor part of the documentation at the SWC sites -- they simply advertise that they are compatible with the various HU brands. Anyone seen such lists?
Real easy. Call Metra technical (or email). Tell them you have a technical presale question. They'll tell you what steering wheel controls work with what car/aftermarket HU. Meta has a list of possible command. Contact them and they'll tell you what works with whatever major brand HU (and model) you're considering. PTT (push to talk) isn't supported by many HU but 13 (on hook) may be adequate for your needs.. 1. Volume Up 2. Volume Down 3. Seek Up/Next 4. Seek Down/Prev 5. Source/Mode 6. Mute 7. Preset Up 8. Preset Down 9. Power 10. Band 11. Play/Enter 12. PTT (Push To Talk) 13. On Hook 14. Off Hook 15. Fan Up 16. Fan Down 17. Temp Up 18. Temp Down People don't want to hear this but people who want maximum integration with the car, and a true factory look, might want a real factory unit. BT mic placement BT steering wheel buttons. Voice commands
Unfortunately, here's the answers I've received: Metra -- we know that for #12 PTT, the Panasonic high end VIC HU's are the only ones we've seen that support this. We don't have any information on whether Sony supports onhook/offhook. You'll have to call Sony. Sony -- "Maybe. We don't guarantee whether it will work or not." He could not even confirm whether or not the Sony unit would support it if the external controller does things correctly. Crutchfield -- Initial response: the Metra ASWC is incompatible with Prius. On further 'push'... they have no information on ANY S/W adapter that works with Prius. BUT they absolutely confirm that the ASWC+Sony works nicely, including BT/Phone controls. Based on that minimal info, I will go ahead and assemble my order. Time to get this show on the road!
