Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> · Tue, 30 Aug 2022 08:03:03 -0700

On 8/30/22 02:52, Florian Feldbauer via Tech-talk wrote:

Hey all,

for a small side project I'm working with a board featuring an ESP32-WROOM-32E module [1].
The module itself has WiFi and an EMAC core which is connected to an ethernet PHY on the board (10/100Mbps).
Also there are some sensors connected to the module.

With 448 KB ROM and 520 KB RAM, this chip seems a bit small
to run much of a "regular" IOC.  You might make it work by
manually striping down to just the CA server and DB core.

fyi. a point of rough comparison for RTEMS/powerpc32

$ size bin/RTEMS-mvme3100/softIoc
   text    data     bss     dec     hex filename
2426405  567300  212745 3206450  30ed32 bin/RTEMS-mvme3100/softIoc

At the moment I have a small program running on the board, that connects to ethernet, gets it's IP via DHCP and starts listening on a TCP port.
If a message is received the corresponding sensor data is send as an answer.

The chip is running a modified FreeRTOS kernel and I started to wonder, if it would be possible to port EPICS on that module.

I looked into FreeRTOS ~recently for an unrelated project.
It is a very bare bones OS.  The main surprise I found is that
there is only an abstraction API covering basic threading
and CPU exception handling.  Not I/O devices.  So eg. no
common UART API.  Certainly no sockets API.  Rather, the
various examples I found were using various SoC vendor
libraries directly.

So as it stands now, you would end up with a FreeRTOS+EspressIF
port rather than a generic FreeRTOS port.

Does anyone have experience with the ESP32 and tried running EPICS on it already?
If not, anyone has an idea for a good starting point for such a project?
A CA server that provides the sensor data as PVs would be enough.

A CA server is a complicated/stateful beast by comparison
with most other protocols.

Maybe start with a Modbus TCP server for it?

https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/protocols/modbus.html

Cheers,
Florian

[1] https://www.espressif.com/sites/default/files/documentation/esp32-wroom-32e_esp32-wroom-32ue_datasheet_en.pdf

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System