Running Zephyr on ESP32
Two weeks ago I started toying around with a development version of SumUp Solo card reader and learning more about embed and hardware in general. Recently, we have launched a new reader, Solo Lite which runs on Zephyr and seemed like an easier entry-point. I don’t have a development Solo Lite at hand but I found a couple unused ESP32 microcontrollers at home. The task for the weekend was simple: get zephyr up and running on and esp32.
First, I followed the official Getting started guide. I only diverged in the dependencies installation step, using Nix instead of Homebrew. In my home-manager config I added the necessary packages:
{ inputs
, outputs
, lib
, config
, pkgs
, unstable
, bleeding-edge
, ...
}:
let
username = "matousdzivjak";
homeDir = "/Users/${username}";
in
{
...
home.packages = [
pkgs.minicom # Modem control and terminal emulation program
pkgs.wget
pkgs.python3
pkgs.ninja # Small build system with a focus on speed
pkgs.gperf
pkgs.ccache # Device Tree Compiler
pkgs.dtc
];
}
(I switched to nix + home-manager quite recently. If you are interested in my whole config checkout github.com/matoous/nix-home)
Next, I update the binary blobs needed for ESP32:
west blobs fetch hal_espressif
With that, the development setup is done and what was left was getting something running on the esp and what’s easier than a hello world. Zephyr comes with a hello world sample application, we don’t even have to write anything ourselves. The sample hello world app can be build using:
west build -p always -b esp32_devkitc_wroom zephyr/samples/hello_world
Resulting into an output ending with:
Generating files from /Users/matousdzivjak/code/github.com/matoous/esp32-zephyr/build/zephyr/zephyr.elf for board: esp32_devkitc_wroom
esptool.py v4.5
Creating esp32 image...
Merged 5 ELF sections
Successfully created esp32 image.
I flashed the ESP32 which was as simple as connecting it to the laptop with and USB-C cable and running:
west flash
The esp blinks a few times and the flashing is done in a couple of seconds. Theoretically, we have the hello world sample app up and running, but better confirm. For that, I connected to the esp using serial port to check the logs. First, minicom needed tweeking as the last device I worked with had a different setup:
sudo minicom -s
This pops up the configuration menu:
+-----[configuration]------+
| Filenames and paths |
| File transfer protocols |
| Serial port setup |
| Modem and dialing |
| Screen |
| Keyboard and Misc |
| Save setup as dfl |
| Save setup as.. |
| Exit |
| Exit from Minicom |
+--------------------------+
Here one needs to configure the Serial port setup:
+-----------------------------------------------------------------------+
| A - Serial Device : /dev/modem |
| B - Lockfile Location : /var/lock |
| C - Callin Program : |
| D - Callout Program : |
| E - Bps/Par/Bits : 115200 8N1 |
| F - Hardware Flow Control : No |
| G - Software Flow Control : No |
| H - RS485 Enable : No |
| I - RS485 Rts On Send : No |
| J - RS485 Rts After Send : No |
| K - RS485 Rx During Tx : No |
| L - RS485 Terminate Bus : No |
| M - RS485 Delay Rts Before: 0 |
| N - RS485 Delay Rts After : 0 |
| |
| Change which setting? |
+-----------------------------------------------------------------------+
Fist, A to modify the Serial device. We need to specify the tty of the connected esp. For me this was /dev/tty.usbserial-0001. I think this might differ for others, so the quick way to check which serial device to use one can run ls /dev | grep 'tty.*usb' and unless there are multiple devices with serial port connected via an USB cable there should be exactly one result.
Once that’s done, Exit, and here it is:
Welcome to minicom 2.9
OPTIONS: I18n
Compiled on Jan 1 1980, 00:00:00.
Port /dev/tty.usbserial-0001, 22:07:30
Press CTRL-A Z for help on special keys
0020 vaddr=00000020 size=0001ch ( 28)
I (113) esp_image: segment 1: paddr=00010044 vaddr=3ffb0000 size=00104h ( 260) load
I (122) esp_image: segment 2: paddr=00010150 vaddr=3�NG early entropy source...
*** Booting Zephyr OS build v3.6.0-1966-g3f218c6cdae0 ***
Hello World! esp32_devkitc_wroom/esp32/procpu
A beautiful, rewarding, and underwhelming Hello World!.
Next I think I will try to run Hello World! with hubris which upon initial investigation seems to be way more complex as esp32 board isn’t supported out of the box. Alternatively, I might try to get Zephyr up and running on a Solo instead. Either way, enough for one evening and more to come.