generated from CubeCraft-Creations/Tracehound
101 lines
4.2 KiB
Markdown
101 lines
4.2 KiB
Markdown
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# ESP-01S firmware updates without a USB-UART adapter
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Status: **design / not yet implemented.** Interim mitigations (config-over-UART,
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GPIO reservation) are shipped; see "Shipped now" below.
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## Problem
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The ESP-01S camera bridge has no native USB. Today it is flashed with an external
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3.3 V USB-UART adapter and a `GPIO0 → GND` jumper held during reset. On an assembled
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field node that is impractical — we want to update it over the network.
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## Why not Wi-Fi OTA on the ESP-01S itself
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1. **Network topology.** The ESP-01S joins the *GoPro* AP (`10.5.5.1`), not the hub /
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travel-router network. The hub cannot reach it to push an OTA.
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2. **1 MB flash.** Standard ESP8266 OTA stages a second copy of the sketch alongside the
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running one. Our sketch is ~333 KB; a 1 MB module has no room for two copies plus FS
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and reserved areas.
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So updates must arrive **through the XIAO**, which is already UART-connected to the
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ESP-01S and sits on the hub network.
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## Approach: XIAO ESP32-C6 as the flasher (UART OTA)
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The XIAO plays the role the USB-UART adapter plays today, driving the ESP-01S's ROM
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serial bootloader over the existing UART.
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### Hardware — two added control lines
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| XIAO pin | → ESP-01S | purpose |
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|----------|-----------|---------|
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| `D8` (`ESP01_RST_PIN`) | `RST` | pulse low to reset the ESP-01S |
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| `D10` (`ESP01_PGM_PIN`) | `GPIO0` | hold low across reset → enter bootloader |
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| `D6` (TX) / `D7` (RX) | `RX` / `TX` | existing `Serial1` link (crossed) |
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| GND | GND | common ground |
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> **Confirm before committing the PCB/wiring:** verify `D8`/`D10` on the actual XIAO
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> ESP32-C6 variant do **not** map to ESP32-C6 strapping pins (`GPIO8`, `GPIO9`, `GPIO15`)
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> or the USB-JTAG pins. Pins are reserved in firmware (`ESP01_RST_PIN`, `ESP01_PGM_PIN`)
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> but not yet driven.
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### Bootloader entry
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`GPIO0 = LOW`, pulse `RST` low→high → ESP-01S enters the serial bootloader on the UART.
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After writing: `GPIO0 = HIGH`, pulse `RST` → run the new firmware. Always restore
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`GPIO0 = HIGH` on give-up so the ESP can boot normally.
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### Flash protocol
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Implement enough of the ESP8266 ROM bootloader / esptool SLIP protocol on the XIAO over
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`Serial1`:
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- `SYNC`, then `FLASH_BEGIN` / `FLASH_DATA` (≈1 KB blocks) / `FLASH_END` to write the app
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at offset `0x0`.
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- Start at 115200 baud; optionally raise after sync.
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- Verify with the ROM `SPI_FLASH_MD5` against the expected MD5.
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### Firmware delivery (hub → XIAO)
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Greenfield on the Go hub (only a `firmware_version` field exists today). Recommended:
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- **HTTP pull.** Hub exposes `GET /firmware/esp01s/<version>.bin` (+ MD5). XIAO is
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triggered by an MQTT command, e.g.
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`{"command":"update_esp01s","url":"http://<hub>/firmware/esp01s/0.4.0.bin","md5":"…"}`,
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fetches the `.bin` in chunks, and streams each chunk straight into a `FLASH_DATA` block.
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- Avoid buffering the whole image in RAM — stream HTTP chunk → flash block → repeat.
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- MQTT chunked transfer is possible but heavier on the broker; prefer HTTP.
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### Sequencing / safety
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- Pause the UART JSON status/command protocol while flashing (the link is busy with the
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bootloader protocol).
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- On failure leave the ESP recoverable and retry; report progress/result to the hub over
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MQTT.
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### XIAO self-update (separate, easy)
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The XIAO (4 MB flash, on the hub network) can use standard ESP32 OTA (`ArduinoOTA` or
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`httpUpdate`). No gymnastics required. Split: **XIAO = native OTA; ESP-01S = flashed by
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the XIAO over UART.**
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## Scope estimate
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- **XIAO firmware:** ESP8266 ROM-loader client over `Serial1` + `GPIO0`/`RST` control +
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HTTP fetch + MQTT trigger. Medium–large.
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- **Hub (Go):** firmware store + HTTP endpoint + MQTT trigger command. Small–medium.
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- **Hardware:** two control wires + confirm non-strapping pins. Small.
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## Shipped now (interim)
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- **Config-over-UART (`set_config`)** — change GoPro SSID/password/IP and poll interval
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with no reflash. Hub → `set_camera_config` (MQTT) → XIAO → `set_config` (UART) →
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ESP-01S persists to LittleFS.
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- **GPIO reservation** — `ESP01_RST_PIN = D8`, `ESP01_PGM_PIN = D10` reserved in the XIAO
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firmware for the flasher.
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## References
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- ESP8266 ROM serial bootloader protocol (esptool).
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- Wiring: Notion "XIAO ESP32-C6 Pin-to-Pin Wiring Diagram".
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