Toyota Bean Network Decode and building device to put data on bus. - Page 1
Forum section: electronics / projects

author: uvamosk
author_rank: Contributor
timestamp: November 08, 2016, 12:00:01 am
content: Hello Guys,Well I'll admit I am way over my head and barely know where to start. So I'll start from the top.I am doing an engine swap on a 2003 Mr2 spyder and have a few issues. The A/C, Temperature gauge and Alternator light are controlled by a system Called Multiplex.My Problem:The A/C system is controlled by the gauge cluster that takes the input from the user (A/C button pushed) and then sends that request over the Multiplex bus to the Engine computer that then turns on and off the A/C.The temperature gauge is controlled by the ECU sending data over Multiplex to the cluster which then moves the gauge needleThe Alternator light is controlled the same way the temperature gauge is but just turns it on and off.My Solution at the time:I built a module (micro controller) that takes the user inputs (A/C button pushed) Reads all the sensors from the dash (all analog) does calculations then provides ground signal to the Non-factory ecu's A/C pin which then turns on the A/CThis solution works but it is not the 1 wire dream I have had from the start. Though it does work and the car has A/C with the engine swap I am just not happy I can't do it with 1 wire and some code.So that leads to me asking for help. I have found only one place on the internet that anyone seems to have decoded it and figured it out.http://www.toymods.org.au/forums/threads/39361-Toyota-BEANs-Multiplex-etc/page3All the research I have done has brought me to the information I have below.Toyota BEAN (Body Electronics Area Network) is used by Toyota on early 2000 model cars and still used somewhat today.Access method: CSMA/CD with bit wise arbitrationError Detection: 8-bit CRCHeader Length: 25bitsData length: 1-11bytesBit rate: 10Kb/sEncoding Method: NRZ with bit stuffingUsing 1 wire communication on a BUSSays protocol can be used by 8bit general purpose MCUI have included 14 pages from SAE that give a large amount of information and at the time is way over my head.I have also Included a Picture of my Scope hooked up directly to the cluster with no ECU hooked up to the bus, so the cluster is putting out this message on the Multiplex bus on its own.My Goals:Is to be able to decode the messages on the bus and send the messages I need to Have my A/C function, Temp gauge work and alternator light go off. This will be done using a Atmega328 or Attiny84 or 85 any of the 3 are more than capable I believe the ATtiny85 could actually do the job at 8mhz.I really appreciate any help on this as I'm going to need it lolI'm going to keep this updated with anything new I figure out and try to keep this info open to everyone.

author: uvamosk
author_rank: Contributor
timestamp: November 08, 2016, 12:05:33 am
content: Rest of SAE paper and scope screen shot.

author: Vgkid
author_rank: Super Contributor
timestamp: November 08, 2016, 01:03:59 am
content: What are you going to swap in place of your 1zz ?

author: uvamosk
author_rank: Contributor
timestamp: November 08, 2016, 02:19:13 am
content: Quote from: Vgkid on November 08, 2016, 01:03:59 amK24a4 vtec killer with Type S cams, then once all my bugs are worked out I got a special K series build I want to do.I got two friends that have theirs already swapped and running both have fully built engines making in the 250whp N/A They are running my A/C module I built to test it for me ^_^One day when I finally pull the trigger on mine I'll be 100% ready to go.This car has been what keeps pushing me further and further down this electronics rabbit hole. About 6 months ago I barely knew anything (First year high school electronics) about Digital Electronics, Now I know a lot more and keep growing everyday lol. Now I'm pushed into this realm of mathematics I never knew existed and is so far above my head but I guess I'll chug away on it like I did not knowing anything about Digital Electronics.