RS232 drop-out between SDC2 and M800 (WRX9-10)

Covers current and earlier Subaru and Mitsubishi Plug-In systems

RS232 drop-out between SDC2 and M800 (WRX9-10)

Postby mrsaturn7085 on Wed Sep 13, 2017 11:01 am

I've been having issues with communications drop-out between an SDC2 and WRX9-10 board. When this happens, the communications simply stop working, however the M800 and SDC2 still function independently of each other.

Live data on the SDC2 shows the manifold pressure data frozen at it's last received value, and all data points received by the M800 (wheel speed, yaw, lat-G, etc.) freeze, as well.

Normally this would just be an annoyance, but since the wheel speed data is tied to launch control, I need to figure out a way to get this fixed...

Any ideas?
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Re: RS232 drop-out between SDC2 and M800 (WRX9-10)

Postby mrsaturn7085 on Wed Sep 13, 2017 11:50 am

Power cycling the SDC2 (white plug pulled/reinstalled) repairs the communication bus (albeit, temporarily) - I'm almost sure the SDC2 is the issue. When first installed, I initially noted some issues with communications between the PC and the SDC2 using a UTC adapter. I'm starting to think all of this is related. A few notes about the SDC2 behavior:

1. 'Open matching config' hangs for a unspecified amount of time stating no device connected before detecting the SDC2; usually 3-5 sec.
2. 'Monitor channels' hangs for a few seconds before opening the monitoring window.
3. 'About' always says "(Device not found)" for device firmware version.
4. Uploading the most recent firmware is possible to do successfully, and when selected it will say 'firmware to upload matches installed firmware; continue?' or something similar.

Aside from this, a power cycling of only the M800 does NOT fix the RS232 connection - after power-cycling, the ECU shows zero for all RS232 received values and the SDC2 retains the last received manifold pressure value; all internal SDC2 values keep chugging along and diff. control still works... the SDC2 just gives up on performing it's RS232 duties.
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Re: RS232 drop-out between SDC2 and M800 (WRX9-10)

Postby SprinterTRD on Wed Sep 13, 2017 11:59 am

Bit hard to say what is wrong. Replace the pins, check wiring as a first item on the check list.

If you have a scope then check the RS232 out of the SDC
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Re: RS232 drop-out between SDC2 and M800 (WRX9-10)

Postby mrsaturn7085 on Wed Sep 13, 2017 12:39 pm

I'll be scoping the signal tomorrow after I snag an o-scope and logic analyzer from the office. At the moment, I don't think it's wiring related - a power cycle shouldn't fix that kind of thing.

I pulled the module and opened the case just to take a closer look - not that it ever helps with SMD stuff... but still - all conformal coating was intact, nothing burned, and the RS232 I/C appears to be a MAX202E which is ESD protected... so there goes that theory.
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Re: RS232 drop-out between SDC2 and M800 (WRX9-10)

Postby SprinterTRD on Wed Sep 13, 2017 1:30 pm

Since the RS232 is a single wire signal requiring the grounds of the ECU and SDC to be at the same potential, It is possible that wiring or grounding issues are causing your problem.

Unplugging the connector & re connection may improve the signal connection however can degrade to a point where it no longer functions.
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Re: RS232 drop-out between SDC2 and M800 (WRX9-10)

Postby mrsaturn7085 on Wed Sep 13, 2017 3:36 pm

The OEM DCCD controller and ECU function without issue, however. If wiring or grounds were the issue, the factory TCM has a tendency to throw codes and open the diff. in short order.
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Re: RS232 drop-out between SDC2 and M800 (WRX9-10)

Postby mrsaturn7085 on Fri Sep 15, 2017 5:28 am

With advice from MoTeC USA, I scoped the signals and the issue is between the SDC2 main microcontroller and MAX202E RS-232 I/C. While the MAX202E is the more common point of failure, it appears the core I/C is the problem and I will be submitting and RMA later today.
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