Documentation
Open CPU: your code on our hardware
Every Smart Meter Adapter can be ordered as an Open-CPU device. It runs an ESP32-S2 that you program freely — no NDA, no licence agreement, no surcharge.
A finished device
Enclosure, power supply, WiFi antenna, meter interface, CE marking and DIN-rail mounting are done. All that is left is your firmware.
Three extensions
M-Bus, Wireless M-Bus and P1/IR are available as interface boards and are detected automatically at runtime.
No strings attached
No NDA, no licence fee, no registration. You buy hardware and do what you like with it.
Pinout
The extension connector signals appear on the following ESP32-S2 pins.
| Signal | ESP32-S2 | Function |
|---|---|---|
BTN / IO0 |
IO0 | Button, also the boot strapping pin |
LED1 |
IO1 | Status LED, channel 1 |
PWR |
IO2 | Supply for the extension board |
LED2 |
IO3 | Status LED, channel 2 |
U1RTS |
IO4 | UART1 RTS; used as CC1101 CS on WMBUS |
U1CTS |
IO5 | UART1 CTS; switches the supply on IR and the enable signal on DSMR |
GPIO0 |
IO6 | Freely usable |
GPIO1 |
IO7 | Hold at 0 on DSMR (4.33 V supply); CC1101 GDO1 on WMBUS |
GPIO2 |
IO8 | Enables the voltage output on DSMR (Iskra meters only); CC1101 SI on WMBUS |
GPIO3 |
IO9 | CC1101 SCLK on WMBUS |
DETECT |
IO10 | ADC input identifying the extension board |
LED3 |
IO11 | Status LED, channel 3 |
U1TXD |
IO21 | UART1 TXD towards the meter; CC1101 GDO2 on WMBUS |
U1RXD |
IO22 | UART1 RXD from the meter |
Extension board detection
The DETECT signal is measured to identify the connected extension. Each board carries its own pulldown resistor for this.
| ADC value | Voltage | Pulldown | Extension |
|---|---|---|---|
| 2258 | 0.30 V | 10 kΩ | MBUS |
| 3526 | 0.43 V | 15 kΩ | WMBUS |
| 6718 | 0.82 V | 33 kΩ | P1 / IR |
Signal use per extension
MBUS- U1RXD and U1TXD carry the communication.
WMBUS- A CC1101 transceiver is driven over SPI: GPIO3 as SCLK, GPIO2 as SI, U1RTS as CS, GPIO1 as GDO1, U1CTS as GDO0 and U1TXD as GDO2.
IR- U1RXD and U1TXD carry the communication; U1CTS switches on the supply voltage for the reading head.
DSMR- U1RXD and U1TXD carry the communication; U1CTS drives the enable signal. GPIO2 switches on the voltage output, which is only needed for Iskra meters. GPIO1 must be held at 0 so that the supply is 4.33 V.
We flash your firmware
On request we ship the devices with your firmware and your configuration already installed.
€200.00 + €5.00 per unit
plus VAT