I'm making a methanol injection controller for my car. I need to split the analog reads of 6 sensors (Manifold Absolute Pressure sensor, Throttle Position Sensor, knock sensor, wide-band O2, methanol level, and a trim adjustment pot) between at least 2 chips. 60mS of delay for the analog to digital converter each time through the loop is a bit high for injector pulses of as little as 5mS. I would gladly use 6 chips if possible, where the master chip would measure the methanol level only until the injector was commanded on, at that point it would switch to a formula to estimate the level and a level switch would act as a safety in case of a leak. At about .7Gs from 0-75 MPH, a level sensor becomes very inaccurate anyway, especially with a manual transmission that has 2 shifts in that range. I've got 14 PSI boost and 10:1 compression with the goal of running 89 octane (R+M/2) pump gas, so methanol delivery will be critical to not sending a rod through the side of the block. I'd like to get this perfect on the first try, I do have a race engine built and ready to drop in if I fail (I'm replacing the current engine before summer anyway), but I'd like to have this engine intact to build up so I have a spare.
My first thought was to daisy-chain the chips (tx1 --> rx2/tx2 --> rx3/tx3 --> ... -->rx1) where the first chip would send a request and the subsequent chips would add their data to an array and pass that along to the next chip with a request for that chip's data to be sent to the next chip and so on until the master chip has all 5 of the other chips readings. Unless I've missed something, I can only send 8 bits at a time, making this idea seem... less good (at best)... maybe impossible. I'd also like to transmit/receive longs, as the .02V resolution of 8 bits is a bit low (no pun intended) for the MAP and O2 sensors. I think it would work with 8-bit, but if it's not a ton more work I'd really like to take advantage of the full capabilities. I know very little about serial communication, so "pretend" you're talking to a complete noob :)