jatgomaja avatar image
jatgomaja asked over rs232 connection not working properly

Hi there,

I am trying to get the ve.Text mode to work, for parsing the data which my SmartSolar MPPT 75/10 is sending out.

I have a setup consisting of a SmartSolar MPPT 75/10, a 100W panel and a 12ah Lifepo4 battery. Connected to it (via a dc-dc adapter) is a raspberry pi zero w with a MA3232 converter (converting the RS232 signal to ttl) which is connected to the port on the charger.

I am trying to keep the hardware footprint as small as possible, which is why I would like to use the raspberry pi serial console and a custom made (short) cable.
Another point is that sometimes drivers from chips connected to the usb-hub affect the dwc-otg driver of the hub. Causing it to hang, which is bad, since the wifi is also connected via the usb-hub...

So to avoid these problems I want to use the uart console of the pi.
Therefor I made my own to RS232 cable as specified in the documentation.

But if I connect from the pi to the serial console (with the help of the MAX3232 converter) I do not get a nice textual representation of the values, as I would expect.

Instead I get this:

I also checked with a usb-to-rs232 converter on my laptop, but the output was the same.

When I tried with an usb-to-ftdi converter I got the desired text output, so what is the difference between the MAX3232 and the FTDI chip?

Does the FTDI do something else with the data?

On the protocol faq page I saw a reference implementation of a framehandler, do I need to run the data through this one first?

I am a little lost here, since all implementations of parsers I was able to find online rely on a usb serial interface...

Help anybody?

SmartSolar MPPT 75/10 Firmware: v1.46
Bluetooth Interface FW: v2.23

MPPT ControllersBMV Battery MonitorVE.Direct
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1 Answer
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jatgomaja answered ·

Ok, no answer in over a month, time to answer my own question then...

Seems to me like I am the only one wanting to use RS232 for communicating with an MPPT?

Anyways, while waiting for an answer I kept scouring the forum and found this post.

which brought me on the right track...

@Victron: I am very grateful that you share that much information about your products and how to interface with them, but if you put in your faq that one can use RS232 to access the protocol (even if you just reference your RS232 Interface cable) you could also mention that it is NOT a standard RS232 communication, but an INVERTED signal. Which would have saved me a lot of time and worries...

When I looked at the RS232 Interface cable I thought it was just an expensive adapter, but it turns out it has some additional circuitry inside the RS232 connector housing (can be seen in this post). This circuit seems to invert the signal, as well as provide galvanic isolation between the charger and the PC side (which is why you would need to power the circuit inside the connector housing via pin 4 and/or pin 7).

I got it working now, using an inverter (74HC14D see here and here for details) before my MAX3232 converter.

I do not get the nice textual representation with this one, but now using a modified parser (thank you Jesse Collis ! ) I can decode the received messages and convert them back to process them.

I hope somebody else will find this information useful.

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joanspark avatar image joanspark commented ·

Just for completeness.. the signal coming out of the VE.Direct port is RS232-TTL compatible and not inverted IMHO.
The logic (high/low) resembles RS232 logic, while the signal levels are 0V and 5V.

The VE.Direct RS232 cable does galvanic isolation (ADuM1201AZR) and then some either very smart power harvesting with a LM555CM timer chip that provides +5V for the ADuM and +/-15V for the TX towards the RS232 connection OR the version I got here is some oddball that is not properly manufactured/designed.

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