GND-Connection between ESP and Mara? about marax_timer HOT 6 CLOSED

Well, I can't explain, but I think you can connect the ground as well, if you know what is the GND pin on the MaraX

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I've been trying to find out what the GND pin is, but no luck so far... ;-)
You don't happen to know that, do you? ;-)

My guess is that it works because the communication is only half-duplex. But it still is just sheer luck.

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Yeah, I have no idea what the GND pin is

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Hi ShuzzDE,

I'm also wondering what type of connection it is. Watching LelitInsider's video I've seen that he is connecting a 4-wire-cable, so it looks like a standard full duplex serial connection (see https://youtu.be/9NL6yeq7sMM )

In all projects on github pin 3 is assumed as RX and pin 4 as TX (see https://github.com/bancbanus/marax_monitor/blob/main/hardware/marax_control_box.png). I've seen that Alexrus is sending data to the RX pin, but in my tests this doesn't have any effect. Maybe pin 3 is the GND pin?

You said that you were trying to find out the GND pin? Can you tell me how you did it? Did you use the multimeter? A logic analyzer or an oscilloscope?

I didn't want to brick the coffee machine (and upset my wife), that's why I didn't do any further investigations. I would be pleased if you can share your insights :-)

I would also like to know if there is a Vout pin which can be used to power the ESP32. Maybe the first pin? Because all V+ pins are labelled as squares on the control box' schematic.

Best regards!

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Actually I think it should be easy to find out.

MaraX has a 6 pin connector, we are using pins 3&4 for RX or TX (but not sure if 3 is RX or TX, depends if you start left to right or right to left)

The standard pinout is 5V, GND, RX, TX, RTS, CTS. So GND should be next to RX

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Hi Alex,

thank you for your answer and yes, you're right :-)

The pinout (from the center to the edge) is most probably 5V, GND, RX, TX, RTS, CTS

BTW it has also been confirmed by larszi who realized a very impressive mod: https://github.com/larszi/marax-pressure-mod

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