Firmware-IEC

IEC 61131-3 Firmware for Poppy Logic Controller

The firmware in this directory allows writing control programs for the Poppy Logic Controller in the IEC 61131-3 textual language ST (Structured Text).

This is made possible by the matiec open-source 61131-3 compiler. This compiler is used to compile the ST code into the C language from where it is then linked against a Rust firmware which drives the I/O.

Running It

The build process is entirely driven by cargo. matiec is installed automatically on first build. The only dependency you need is, as for the Rust firmware, elf2uf2-rs:

cargo install elf2uf2-rs

Then, put the Pico into bootloader mode by first pressing the BOOTSEL button and then, while keeping it held down, pressing the reset button.

Now you can build and deploy your 61131-3 firmware:

cargo run

Programming Quickstart

You might want to read up on the basics of ST somewhere first. I am going to detail some matiec and Poppy Logic specific things in this section of the README.

The program is found in src/main.st. In contrast to a lot of PLC programming IDEs, the entire ST program must be written here, including the top-level program and configuration (which is usually handled in GUI). You can take the existing code as a basis. Your top-level code goes into the body of the PROGRAM.

Further tasks and function blocks can also be added to main.st. Alternatively, you can put them in separate files and include those using:

{#include "filename.st"}

For I/O, the following tags exist and map to the Poppy Logic Controllers 16 inputs and 16 outputs:

• Inputs: %IX00, %IX01, %IX02, %IX03, %IX04, %IX05, %IX06, %IX07, %IX08, %IX09, %IX10, %IX11, %IX12, %IX13, %IX14, %IX15
• Outputs: %QX00, %QX01, %QX02, %QX03, %QX04, %QX05, %QX06, %QX07, %QX08, %QX09, %QX10, %QX11, %QX12, %QX13, %QX14, %QX15

Byte-access or word-access to these tags is not possible.

Modbus

This firmware also comes with a Modbus RTU interface for interaction with other devices. The interface is available over USB, where the Poppy Logic Controller will announce itself as a serial port.

A few registers are mapped to Modbus for communication:

• Modbus Coils 0 - 15 of unit 1 are mapped to %MX00 - %MX15.
• Modbus Holding Registers 0 - 15 of unit 1 are mapped to %MW00 - %MW15. Holding registers are 16 bits wide.

Additionally, the state of all inputs and outputs is available read-only through Modbus discrete inputs:

• Inputs %IX00 - %IX15 are mapped to discrete inputs 0 - 15.
• Outputs %QX00 - %QX15 are mapped to discrete inputs 16 - 31.

(This may be useful for visualization purposes).

As a quick example, using the pymodbus REPL you can set coils or dump the state of inputs and outputs:

$ pymodbus.console serial --port /dev/ttyACM0

> # Set a coil
> client.write_coil unit=1 address=0 value=1
> # And reset it again
> client.write_coil unit=1 address=0 value=0

> # Or dump all physical inputs and outputs
> client.read_discrete_inputs unit=1 address=0 count=32
{
    "bits": [
        false,
        false,
        ...

Modbus Monitor GUI Example

To demonstrate the Modbus communication, I added a small GUI example: modbus_monitor.py