Megasquirt CAN

Megasquirt Dashboard CAN broadcast

This CAN script enables integration with the simplified dashboard mode CAN stream. Refer to the Megasquirt documentation for enabling Dashboard mode CAN broadcast.

Channels enabled:

• Engine RPM (RPM)
• Throttle Position (TPS)
• Coolant Temperature (Coolant)
• Manifold Absolute Pressure (MAP)
• Air/Fuel Ratio (AFR)

Additional channels can be enabled by expanding the script.

CAN Database

CAN Bus database for Megasquirt

Megasquirt Wiring

MS3-Pro MS3-Pro wiring

CAN bus connections available on MS3-Pro white connector:

• CAN High: Pin 34
• CAN Low : Pin 33

Photos

--This example configured for Megasquirt Dashboard Mode

--how frequently we poll for CAN messages
tickRate = 30
--the CAN baud rate
CAN_baud = 500000
--CAN channel to listen on. 0=first CAN channel, 1=second
CAN_chan = 0
--1 for Big Endian (MSB) mode; 0 for Little Endian mode (LSB)
be_mode = 1

--add your virtual channels here
--addChannel(<name>, <sample rate>, [logging precision], [min], [max], [units label])
rpmId = addChannel("RPM", 10, 0, 0, 8000)
tpsId = addChannel("TPS", 10, 0, 0, 100, "%")
mapId = addChannel("MAP", 10, 0, 0, 105, "kPa")
cltId = addChannel("Coolant", 1, 0, 0, 250, "F")
afrId = addChannel("AFR", 10, 1, 0, 20)

--customize here for CAN channel mapping
--format is: [CAN Id] = function(data) map_chan(<channel id>, data, <CAN offset>, <CAN length>, <multiplier>, <adder>)
CAN_map = {
[1512] = function(data) map_chan(mapId, data, 0, 2, 0.1, 0) map_chan(rpmId, data, 2, 2, 1, 0) map_chan(cltId, data, 4, 2, 0.1, 0) map_chan(tpsId, data, 6, 2, 0.1, 0, filter_tps) end,
[1514] = function(data) map_chan(afrId, data, 1, 1, 0.1, 0) end
}

function onTick()
    processCAN(CAN_chan)
end

function filter_tps(value)
  --filter out overflow
  if value > 100 then value = 0 end
  return value

end

--===========do not edit below===========
function processCAN(chan)
    repeat
        local id, e, data = rxCAN(chan)
        if id ~= nil then
            local map = CAN_map[id]
            if map ~= nil then
                map(data)         
            end
        end
    until id == nil
end

--Map CAN channel, big endian format
function map_chan(cid, data, offset, len, mult, add, filter)
    offset = offset + 1
    local value = 0
    while len > 0 do
        value = (value * 256) + data[offset]
        offset = offset + 1
        len = len - 1
    end
    local cv = value * mult + add
    if filter ~= nil then cv = filter(cv) end
    setChannel(cid, cv)
end

initCAN(CAN_chan, CAN_baud)
setTickRate(tickRate)

References

• Full CAN bus mapping