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Author Topic: Trace/Xantrex SWCA comms protocol  (Read 2763 times)
clivejo
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« on: July 11, 2012, 12:42:14 PM »

I've been looking into trying to connect my RPi up to my Trace SW series inverter.  The instructions recommend using a special interface which is too expensive for my budget.  But after reading a bit about it, apparently its just serializes the data from a remote display/control.  I had a wee look and sure enough the remote connector on the inverter is just a second display output.

I have a burnt out internal display I had to replace a while ago and it looks pretty simple.  Basically an LCD and some latches to manage the inputs.  Anyone able to help me build an interface?

Basically it needs to read the raw LCD data, to feed into the Pi then issue the button presses to control the inverter.

PS : The soldering on the latch, bottom-right was my attempt at fixing, using a soldering iron too big for the job!  Please ignore my sloppy work!



* TraceDisplay.jpg (84.19 KB, 977x447 - viewed 401 times.)
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jonesy
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« Reply #1 on: July 11, 2012, 02:49:41 PM »

Don't know this inverter, but know quite a lot about displays.  It *looks* like a generic type.  All the ones I've used follow the Hitachi HD44780 protocol.(http://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controller)  Assuming that the custom graphic option was not enabled, you should 'just' be able to catch the 8 bit (ascii) data (it could be configured in 4 bit mode) using the clock input.  I'd probably use a PIC say a smallish 16f874 to then squirt it to serial usb converter that Rpi could catch.  If you fancied a challenge you could use the 18f4550 with a built in usb controller, but then you'd need the linux driver.  Sounds painful.  KISS.

Do you have a good photo of the proper interface to get chip numbers off?  SMA published such good quality ones for their interface, you could almost trace the PCB!

So that hasn't really answered your question.  What kind of help d'you need?

Thinking about Rpi myself..
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clivejo
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« Reply #2 on: July 11, 2012, 03:24:12 PM »

I read that the LCD is just an 8 bit ASCII stream.  Each menu item normally has a code for example 3.1.  If the RPi held a MIB detailing the menus, its could use the first few characters to navigate the menus providing I find a way for the RPi to manipulate the button presses.  This is what I need help with!

Here is an example MIB for the menu structure - http://www.welcomehome.org/senecass/software/powerguru/XANTREX-MIB.txt
« Last Edit: July 11, 2012, 03:30:06 PM by clivejo » Logged



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jonesy
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« Reply #3 on: July 12, 2012, 09:28:36 PM »

I think I am very quickly out of my depth! I can see what the mib does but that's it. I note it's got a reference to SNMP - is that significant? Don't think I can help you.  Sorry
AN
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clivejo
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« Reply #4 on: July 12, 2012, 09:42:41 PM »

I think I am very quickly out of my depth! I can see what the mib does but that's it. I note it's got a reference to SNMP - is that significant? Don't think I can help you.  Sorry
AN

No, dont worry about that!  That's just software, its how I propose decoding the ASCII stream within software and perform the logging, control etc

Can you explain the 8bit latches and how they encode the input from the 8 buttons and also the 8 output LED's?
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