AutoXer

iTrader: (1)

I know MUTIII runs 15,625bps at the default rate. I also know that you can alter the ROM to make it run at 65200bsp. But, what is the actual throughput? How long does it take on average to send/rec one Request/Response pair at the default rate? The max I can get using ecuEdit is ~31ms logging 1 parameter.

Am I correct in assuming the following?
Request = 8 bits
Response(echo) = 8 bits
Response(data) = 8 bits

Are there start, stop and parity bits in there?

MalibuJack

iTrader: (5)

Yep in general every byte replies with 2 bytes (actually its an echo and a byte, but same difference)

No parity, no flow control, framing markers don't really exist as its not a true RS232 protocol, ECU Latency is the only thing you'll experience. It will be approximately 4x faster than the 15kbps setting. basically its 8n1 setting for standard RS232.

Not every logger actually can log at that speed though. I have verified Mitsulogger can though.

jcsbanks

Evoscan can do about 150-180 items per second, Mitsubishi logger seems similar, just that Evoscan displays it so you're aware.

However, at 15625 with 2x10 bits for each item (echo is at the same time as the send), if there was continual transfer we should expect 781 items logged per second. I think there is a timer in the ECU that only processes MUT requests so often, but the baud rate isn't really the hold up I think.

I have been wondering about just running 57.6kbps (a very common baud rate) on a new custom protocol that doesn't need fancy init procedures so it connects immediately, and just has two basic commands in 7 byte packets:

Command, Address0, Address1, Address2, Address3, Data0, Data1

One command is read, the other is write. On a read, Data0 and Data1 will be the word reply, on a write, Data0 and Data1 will be the sent items.

If running continuously the rate would be 823 items per second.

There is a DMA function that can work with the serial port on the ECU as well which would keep the overheads down off the CPU.

Presently for reading large maps the data transfer rate is a little bit of a limit, and for road dyno functions the frequency of reading items like RPM and the resolution of them at only 31.25 RPM is lacking.

MalibuJack

iTrader: (5)

That correlates with my observations, I get 7-8 lines per second logged when there are 10-15 MUT items per line at the 15625bps rate.

jcsbanks

Is the Echo a hardware feature that is just because the Rx and Tx lines are tied together? If I connect the terminal emulator at 9600 or 19200 baud on 8N1 to COM1 which the Tactrix cable appears on I get an echo of what I type with the ignition off, but not with the ignition on. Also 57600 doesn't echo at all...

MalibuJack

iTrader: (5)

I just assumed the echo was due to the lines tied together.. I'd guess the echo at 57600 is probably not working because its clobbered, without any handshake speeds above 19200bps tend to lose data..