To connect my PowMr solar inverter to Home Assistant, I needed some kind of adapter in between. I decided for ESP32C3 with Tasmota firmware.

• https://github.com/arendst/Tasmota

Tasmota was comparatively easy to download and translate on my PC. Tasmota comes with a universal interface for ModBus devices such as PowMr. However, the ModBus register names and formats must be given in a kind of script. Register and HW interface of my PowMr inverter was nicely analysed by

• https://github.com/odya/esphome-powmr-hybrid-inverter?tab=readme-ov-file

Recommended IDE for Tasmota is VS code. You need to install PlatformIO framework before opening Tasmota GIT repository. These settings in file platformio_override.ini were needed to translate Tasmota for my ESP32C3 on my Windows PC.

platformio_override.ini

[platformio]
; For best Gitpod performance remove the ";" in the next line. Needed Platformio files are cached and installed at 
  first run
core_dir = .platformio

All other changes I could concentrate in file ..\tasmota\user_config_override.h without really touching the Tasmota code.

user_config_override.h

#ifndef USE_SCRIPT
#define USE_SCRIPT
#endif
#define USE_SCRIPT_JSON_EXPORT
#ifndef USE_SML_M
#define USE_SML_M
#endif
#ifdef USE_RULES
#undef USE_RULES
#endif
 
#define USE_DISPLAY                          // Add Display Support (+2k code) display ON/OFF button
#define USE_UNIVERSAL_DISPLAY                // new driver with display.ini file 

Many FW upload tools failed for my ESP32C3, but the direct USB upload from VS Code worked well.

In the code base I also found the display driver SH1106_display.ini which I renamed to display.ini and uploaded it to the file area of my tasmotized ESP32C3. There is another magic setting you have to apply to any unused GPIO:

The display has another ON/OFF buttom on Tasmotas main screen. Now I started the display with the following commands on the console.

console commands

I2Cscan
displayaddress 0x3c
DisplayModel 17       (new driver with display.ini file and OptionA3)

I needed the script to access my Modbus based solar inverter PowMr. PowMr inverter are all very similar. Luckily

• https://github.com/leodesigner/powmr_comm

investigated already on the registers for these PowMr inverters.

This Tasmota Scripting was the most ugly part of the project.

1. Section >M needs to define Tx and Rx-Mask at different lines and locations which makes the code unreadable
2. Values from section >M can only be used in section >T, not in section >S or elsewhere
3. If values received from section >M are real values(e.g. 0.1), they cannot be used in section >T - only integer allowed
4. calculations in section >T are ignored by the script. Calculations must go into section >S
5. spaces in calculations and some other places are not allowed
6. once section >M is working, the defined units are missing in Home Assistance (due to missing key unit_of_measurement)

However, if you copy the following script, you will be able to - at least see all values in Home Assistant as Tasmota Integration. This script is copied directly into the HTML-script page of the Tasmota device.

Tasmota Script.txt

; GPIO's auf NONE stellen!
 
>D           ;defines
temp=0
AC_Voltage=0
PV_Voltage=0
Batt_Volt=0
Batt_Volt10=0
Chg_current=0
DChg_current=0
Batt_current=0
Batt_Asec=0
Batt_Ah=0
Chg_power=0
DChg_power=0
Batt_power=0
AC_freq=0
val2=0
val3=0
 
>B                 ; at boot
->DisplayText [zs1l1c1]Temperatur innen[s1l3c12]o[s2l2c7]C
->sensor53 r       ; d1 for debug, !!OR!! r for normal operation of ModBus driver
->sensor53 l3      ; LED3 blinken lassen
 
>T                 ; on Tele message
temp=DS18B20#Temperature    ; read temperature
->DisplayText [s2l2c2]%1temp%
;print %temp%
 
Batt_Volt10 = PowMr#Batt_Volt10 ; read values from section >M
Chg_current = PowMr#Chg_current
DChg_current= PowMr#DChg_current
 
>S                 ; 1sec
Batt_Volt=Batt_Volt10/10
Batt_current=(Chg_current-DChg_current)
Batt_power=(Batt_current*Batt_Volt)
Chg_power=Chg_current*Batt_Volt 
DChg_power=DChg_current*Batt_Volt
Batt_Asec+=Batt_current                   ; each second!
Batt_Asec=mp(Batt_Asec <0 0 >(250*3600) (250*3600))  ; 250Ah Battery limit
Batt_Ah=Batt_Asec/3600
print %Batt_Volt%V, %Chg_current%A, %DChg_current%A, %Batt_current%A, %Batt_power%W, %Batt_Ah%Ah
 
=>Publish tele/%topic%/SENSOR {"Batt":{"Chg_power":%0Chg_power%,"DChg_power":%0DChg_power%,"power":%0Batt_power%,"current":%0Batt_current%}}
=>publish stat/%topic%/RESULT {"Batt":{"Chg_power":%0Chg_power%,"DChg_power":%0DChg_power%,"power":%0Batt_power%,"current":%0Batt_current%,"level_Ah":%0Batt_Ah%}}
 
>M 1               ; using 1 meter
; +<No>,<rxGPIO>,<type>,<flag>,<parameter>,<jsonPrefix>,<txGPIO>,<n x 100msec>,i x <hex Telegrams>
+1,20,m,0,2400,PowMr,21,3,05031196,05031198,0503119A,0503119C,0503119E,050311A0,050311A2,050311A4,050311A6,05031195,050311B6,050311B8,050311C8,050311CA,050311CC
1,050304uuUUxxxx@i0:10,AC Voltage,V,AC_Voltage,1
1,050304xxxxuuUU@i0:10,AC Frequenz,Hz,AC_Freq,1
1,050304uuUUxxxx@i1:10,PV Voltage,V,PV_Voltage,1
1,050304xxxxuuUU@i1:1,PV Power,W,PV_Power,0
1,050304uuUUxxxx@i2:10,Battery Voltage,V,Batt_Voltage,1
1,050304uuUUxxxx@i2:1,Battery Voltage10,V,Batt_Volt10,0
1,050304xxxxuuUU@i2:1,Batt Percent,%%,Batt_Percent,0
1,050304uuUUxxxx@i3:1,Batt Charge Current,A,Chg_current,0
1,050304xxxxuuUU@i3:1,Batt DisCharge Current,A,DChg_current,0
1,050304uuUUxxxx@i4:10,Load Voltage,V,Out_Volt,1
1,050304xxxxuuUU@i4:10,Load Frequ,Hz,Out_Freq,1
1,050304uuUUxxxx@i5:1,Load Power VA,VA,Out_PowerVA,0
1,050304xxxxuuUU@i5:1,Load Power,W,Out_Power,0
1,050304uuUUxxxx@i6:1,Efficiency1,%%,Eff1,0
1,050304xxxxuuUU@i6:1,Efficiency2,%%,Eff2,0
1,050304uuUUxxxx@i7:1,Stat4516,dec,Stat4516,0
1,050304xxxxuuUU@i7:1,Stat4517,dec,Stat4517,0
1,050304uuUUxxxx@i8:1,Stat4518,dec,Stat4518,0
1,050304xxxxuuUU@i8:1,Stat4519,dec,Stat4519,0
1,050304uuUUxxxx@i9:1,Stat4501 SBU,dec,Stat4501,0
1,050304uuUUxxxx@i10:1,Stat4534,dec,Stat4534,0
1,050304xxxxuuUU@i10:1,Stat4535,dec,Stat4535,0
1,050304uuUUxxxx@i11:1,Stat4536,dec,Stat4536,0
1,050304xxxxuuUU@i11:1,Stat4537,dec,Stat4537,0
1,050304uuUUxxxx@i12:1,Stat4552,dec,Stat4552,0
1,050304xxxxuuUU@i12:1,Stat4553,dec,Stat4553,0
1,050304uuUUxxxx@i13:1,Stat4554,dec,Stat4554,0
1,050304xxxxuuUU@i13:1,Stat4555,dec,Stat4555,0
1,050304uuUUxxxx@i14:1,Stat4556,dec,Stat4556,0
1,050304xxxxuuUU@i14:1,Temperatur,°C,Stat4557,0
#

PowMr inverter lacks the AC input power measurement. For this reason I added a PZEM004 module for power measurement, which is already fully supported by Tasmota - simply by selecting Rx and Tx-PZEM004 in the Tasmota pin configuration menue.