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Post Info TOPIC: Serial port 3 protocol on sh7052 ecus to read RAM ?


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Serial port 3 protocol on sh7052 ecus to read RAM ?

Having found that the busa ecu can read RAM variables using the serial port 3. Would be interesting to hear if that is possible on other sh7052 based ECU:s ?

The protocol looks like following, but I am not a really specialist in Renesas so this needs much more work:

if sending 0x10, 0x10, 0x10.... you should get a return:
 0x10, 0x05, 0x14, 0x53, checksum

This I am a bit unsure, but something along this:
If sending 0x13, how many variables(max 10), ramvar, ramvar, ramvar
where ramvar is the number of which of the 0x53 first ram variable addresses you should get in return the ram variable 0xFFFF8xxx contents. If value of ramvar is more than 0x53 you should get the ROM ID string (8 bytes) ????

Looks like busa ecu has tuning tools built in - i.e. ability to see the TPS position and various compensations values just sending values to the serial port. This is interesting if we can find out the details. Makes dyno tuning much more easier as there is no need to notch the ecu for reading key values.

If it exists in Busa ECU I would think that Denso has implemented something alike to other ecus too - if the hardware is connected. The only problem is that I have not been able to find how the RS232 speed is set. And at the end of the call there is somekind of reset of timers ... maybe to autoset the protocol speed ???


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Couple of findings:

- The Txd3 speed seems to be around 7500baud, that gives the most consistent results. So I assume Rxd3 is about 7500 as well.
- The interrupts that are set at the end are just resetting the gauge data stream output interval on Txd3.
- In earlier models the harness connector 56, Code, was conencted to receive for alike purpose. In this 32 bit sh7052 ecu its has parts missing and its connected to Rxd2. There is no interrupt subroutines for Rxd2 either.
- The Rxd3 goes to IC102 and without knowing that circuit I can not further trace the signal.

It is possible that Rxd3 is somehow related to the AFC IC801 (air fuel computer) which is missing from USA ecu models.

Anyway for tuning purposes its propably best to use rxd1/txd1 like RR said earlier ...


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