Support multiple parallel PZEM004T sensort - older gen

[sle118]

Describe the problem you have/What new integration you would like

I am designing a circuit which will allow connecting up to 8 PZEM004T sensors in parallel and communicate individually to them using their unique address. Each device has a unique address that is set beforehand using a TTL adapter or some other method of sending the "set address" command.

Please describe your use case for this integration and alternatives you've tried:

I am looking to get detailed/whole house energy usage breakdown from a large electrical panel and feed these into Home Assistant so I can better understand the energy usage patterns and see where I could reduce it. There's a number of possible alternative to using esphome (for example ESPURNA), but the esphome platform seems really mature and diverse enough that I wish to use it going forward. Alternatively, I could probably setup a single ESP8266/ESP32 for each PZEM004T, but this would be quite a bit wasteful.

Additional context

I'm very familiar with embedded development and I am willing to implement the feature myself and eventually send a PR for upstream merging. However, I'd need some guidance on the best way to achieve my goal from a design perspective. For instance:

• Would it be better to wrap the existing PZEM004T class that would orchestrate the interactions and minimize the impact to the existing class, or should I extend the existing class and implement an array of readings for it?
• The end goal is to be able to identify individual circuits with a name that makes sense, for example water heater, which will lead to havnig current, voltage, energy, tracked for the water heater. Each circuit will be uniquely identified by its "address". For example, the water heater sensor could have been pre-configured with 1.1.1.1, whereas the clothes dryer would be configured with 1.1.1.2, etc.
• To simplify configuration, I would want to organize the setup of each circuit with a name, an address, along with the existing PZEM004T object configuration. The name should be used as a prefix to the reported data, but overwriting each reading name would also be possible, just like it is today.
• Finally, I'd like to know what is the shortest development path for this. My current setup is a supervised instance of home assistant running on a RPi 4, and my main dev box is Windows 10 on VS-Code. I'm used to working bare-bone on the esp-idf, but I also have a bit of experience using PlatformIO, which I believe is the platform that this project uses.

The parallel communication to older gen units was tested on espurna and known to be working. More specifically, the author of the code has provided some starting ideas for a communication bus using Schottky diodes.

// Needed when connecting multiple PZEM004T devices on the same UART
// *You must set the PZEM004T device address prior using this configuration*
//
// +---------+
// | ESPurna |                                             +VCC
// |   Node  |                                               ^
// | G  T  R |                                               |
// +-+--+--+-+                                               R (10K)
//   |  |  |                                                 |
//   |  |  +-----------------+---------------+---------------+
//   |  +-----------------+--|------------+--|------------+  |
//   +-----------------+--|--|---------+--|--|---------+  |  |
//                     |  |  |         |  |  |         |  |  |
//                     |  |  V         |  |  V         |  |  V
//                     |  |  -         |  |  -         |  |  -
//                   +-+--+--+-+     +-+--+--+-+     +-+--+--+-+
//                   | G  R  T |     | G  R  T |     | G  R  T |
//                   |PZEM-004T|     |PZEM-004T|     |PZEM-004T|
//                   |  Module |     |  Module |     |  Module |
//                   +---------+     +---------+     +---------+
//
// Where:
// ------
//     G = GND
//     R = ESPurna UART RX
//     T = ESPurna UART TX
//     V = Small Signal Schottky Diode, like BAT43,
//         Cathode to PZEM TX, Anode to Espurna RX
//     R = Resistor to VCC, 10K

https://github.com/xoseperez/espurna/blob/dev/code/espurna/sensors/PZEM004TSensor.h

I have attempted to connect more units in parallel, but quickly came to realize that the ESP8266's poor GPIO's would just be unable to drive the leds of 8 opto couplers. So I came with possible solution for the Tx side of the ESP32, which I'll be using for this project: (edit: changed the Tx MOSFET to N Connector Type)

I will be able to confirm (or not) when I get my boards from JLCPCB in a few weeks (hopefully).

Thank you for helping me getting started with coding the enhancement!

Below is the circuit design that I have sent to production yesterday. My intention is to make the design publicly available when I have debugged all the hardware issues (this is the 1st batch of the design and I expect some magic smoke to come out of at least one of the units or, at best, to see that something is wrong and that I have to do some rework/changes).

edit: Updated board rendering to new version

[sle118]

So I've received my boards.

Any inputs here would be appreciated.

[sle118]

I ended up purchasing pzem004t v3, which can be configured with multiple sensors each with its own address. I'll edit the final MOSFET connection which works great now