Innovate Motorsports OT-2 SDK - Manual (Page 45)

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J1850
The general flow with J1850 Expert Mode (‘e’<2>), is:
1. Select a ‘rate’ (PWM or VPW, really selecting rate, voltage and encoding)
2. Setup filters for the J1850 packets you are interested in
3. Output a packet and (optionally) wait for a designated number of response packets
The export mode commands to accomplish these tasks are:
Command ‘R’ – Set the Protocol Rate
Sent: 2 bytes
{
U8 Cmd; // ‘R’
U8 Rate; // 1 = VPW
// 2 = PWM
}
Responds:
1 byte
{
U8 Result; // Should match ‘Rate’ requested
}
Notes:
J1850 has no default rate so you must set one. In addition,
this command CAN FAIL (result does not match request). The
reason is that the command checks if the required line(s)
ever go idle. If they don’t, the command is failed, because
attempting to transmit would hang.
Command ‘r’ – Get the Protocol Rate
Sent: 1 byte
{
U8 Cmd; // ‘r’
}
Responds:
1 byte
{
U8 Result; // Current rate
// 0 = none
// 1 = VPW
// 2 = PWM
}
Notes:
There is no default rate for J1850 and Set Rate (‘R’) can
fail (see above).