# ESP32 Serial Swiss Army Knife

![ESP32 Serial Swiss Army Knife logo](/images/logo.png "ESP32 Serial Swiss Army Knife")

Universal wireless serial adaptor firmware for the ESP32-S3.

## Initial hardware target

- ESP32-S3-DevKitC-1-compatible development board
- ESP32-S3-WROOM-1-N16R8 module
- 16 MB flash
- 8 MB octal PSRAM
- Adafruit MAX3243 full-pinout RS-232 breakout, product 5988

The current firmware is a command-driven **Phase 0 hardware-characterization harness**. It validates the MAX3243 breakout, its three drivers, its five receivers, valid-signal detection, active-low shutdown, and UART1 loopback before development of the wireless serial firmware begins. Tests run only when explicitly requested at the console; booting the board does not start an electrical test.

## Hardware wiring

See [`wiring.md`](wiring.md) for the hardware profile, GPIO assignments, loopback diagrams, safety notes, and the recommended test sequence. The initial profile covers the ESP32-S3-DevKitC-1 N16R8 and the Adafruit MAX3243 full-pinout RS-232 breakout.

## Build

```sh
pio run
```

## Upload and monitor

Connect the board's USB-to-UART port, then run:

```sh
pio run --target upload
pio device monitor -b 115200
```

The firmware starts an interactive console on UART0. Type `help` to display command descriptions. The Phase 0 commands are:

```text
status
transceiver <enable|disable>
drivers <tx 0|1> <dtr 0|1> <rts 0|1>
loopback-a
loopback-b
valid-test
uart-loopback <baud> [8N1|8E1|8O1|8N2|7E1|7O1] [bytes]
uart-suite
```

`uart-loopback` defaults to `8N1` and 256 bytes. Its accepted payload range is 1–512 bytes. `uart-suite` covers 300 through 250000 baud and all supported frame formats. Follow the applicable loopback wiring in [`wiring.md`](wiring.md) before invoking a test.

The onboard RGB LED reports the most recent test-harness state:

| Color | Meaning |
|---|---|
| Blue | Idle; waiting for a command |
| Yellow/orange | Test running |
| Green | Last test passed |
| Red | Last test failed |

This hardware profile uses the onboard RGB LED on GPIO48. Official ESP32-S3-DevKitC-1 v1.1 boards commonly use GPIO38 instead, and compatible boards or clones may vary. A different board revision requires an adjusted board pin profile before running this firmware.

## License

This project is licensed under the [GNU General Public License version 3 only](LICENSE) (`GPL-3.0-only`). This is compatible with using the GPLv3 releases of wolfSSL and wolfSSH later. Third-party components remain subject to their respective licenses.