question

oli-1 avatar image
oli-1 asked

Logic level of Phoenix 12/500 VE.Direct to connect to an ESP32/ESP8266

Hello,


I want to read out my Phoenix 12/500 with an ESP32 e.g. via https://github.com/cterwilliger/VeDirectFrameHandler or https://github.com/RalfJL/VE.Direct2MQTT

I wonder if I need a level converter or if the VE.Direct port of the inverter is already using a TTL voltage 3.3V.

Did anyone already connect the Phoenix via an ESP8266 or ESP32?



Thanks

Oli


PS: https://www.victronenergy.com/live/vedirect_protocol:faq#q4is_the_vedirect_interface_33_or_5v doesn't answer this question for the Phoenix inverters:


Q4: Is the VE.Direct interface 3.3 or 5V ?

It depends on the product: some are 5v, others 3.3.
The circuits in our panels and USB interfaces work on both voltages. And they automatically adapt their TX voltage to the voltage level coming from the VE.Direct product (bmv/mppt/inverter/etc).

List of the products:
BMV-700: 3v3
MPPT all models: 5v
Newer MPPTs (as now under development) will remain 5V.
Phoenix InverterVE.DirectMQTTarduino
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I have moved this question to the "Modifications" space so it can be seen and possibly addressed by other users experimenting with non-expressly-supported systems/interfacing.

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2 Answers
wkirby avatar image
wkirby answered ·

I'm pretty sure it's 5V TTL. I'll see what I can find out.

Having said that, it's a good idea to isolate the signals anyway and this will deal with the level shifting at the same time. Use something like a Si8422 for digital isolation and level shifting. The VE.Direct port can power its side of the Si8422 directly.

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mtnscott avatar image mtnscott commented ·

I'm looking for a quad isolator and I see SiLabs has a newer quad version - Si8642. It comes in two versions (Default High or Low output) and the one you specified Si8422 is a default High output. Could you confirm that we want the default High output version of the quad chip - Si8642ET-IS?

https://www.silabs.com/isolation/digital-isolators/si86xxt-digital-isolators

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wkirby avatar image wkirby ♦♦ mtnscott commented ·

I have actually used the Si8422 when interfacing with Victron VE.Direct products in the past, so I would suggest the default high version.

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muelli avatar image
muelli answered ·

I have a similar question. As the si8422 is only available as a SMD package, I thought about using some cheapo optocouplers like the 4N33 for that purpose and wondered, if the TX pin can drive the LED for transmit (5mA should work OK).

As this will invert the signal, it will later be inverted again using a N-Channel Mosfet (BS170) so it won't mess up the serial connection. Hope everything is fast enough for 19k2 :D


edit: 4N33 could actually be too slow. 4N25 switches twice as fast with 2µs ON/OFF, so this would actually be much better and give some reserve for the invert later on.

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