> Don't use the mid range reference manual for detailed electrical specs. Depending on the process used in the PIC you have, these details can change, you should always use the datasheet for these values. I hadn't found it before, but an electronic search of the datasheet turned it up. > Also, you have looked at the maximum voltage on Vref+, but you haven't checked the minimum voltage which is rather more important for your application. This is typicaly AVdd-2.5v so you would be out of spec with a 5volt supply. The midrange only had maximums, the actual 'F87XA has minimums too and you're right, the minimum for Vref+ is AVdd-2.5v so in my case 2.5 volts (Vdd is 5v) > Thirdly, you should be able to get a fixed separation between the buttons irrespective of the reference voltage, by selcting suitable resistors. Unfortunatly the resistors are selected for me by the car manufacturer, I cannot change them (I will need to restore the stock radio at some point) If it was left to me I'd either implement a bus protocol of some kind or use a simple R/2R ladder to get maximum spread. Thanks for your help with this, I guess it's back to the thinking room on this for a while, I was really hoping to see if I could get a wider spread by taking Vref lower. -- Anthony Toft I'm Anton, and I approve this message -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist