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espresso_frame/docs/hardware.md
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Firmware: OTA client, dual-board build (devkit/XIAO), version reporting, XIAO fixes
- version.txt + esp_app_desc_t version reporting (X-Frame-Version header);
  new ota_update.c checks the server's advertised version against the
  running one and streams+applies an update via esp_https_ota, gated by
  bootloader rollback (marks the image valid only after a full successful
  cycle, so a bad update can't brick a wall-mounted frame).
- Dual-OTA partition tables: partitions.csv (8MB dev board, 2MB slots) and
  new partitions_xiao.csv (4MB XIAO, 1.875MB slots -- the dev board's
  table doesn't fit the XIAO's flash). New build_for_board.sh gives each
  board its own build dir + generated sdkconfig via SDKCONFIG_DEFAULTS
  layering, so switching boards never clobbers the other's config.
- fetch_photo_info()/fetch_face_labels() were using the short
  reachability-check timeout even though the manage-menu path can be the
  first (cold, TLS-handshake-paying) request of a wake cycle -- switched
  to the longer fetch timeout to stop spurious ESP_ERR_HTTP_CONNECT
  failures.
- XIAO: the RF switch that selects onboard vs. external antenna
  (GPIO3/14) isn't initialized by plain ESP-IDF the way Seeed's Arduino
  package does it, leaving WiFi unable to reliably reach the antenna at
  all -- new board_antenna.c powers the switch and selects the onboard
  antenna, gated behind FRAME_XIAO_ANTENNA_INIT (on by default in
  sdkconfig.xiao). Also remaps the EPD DC/RST/BUSY pins, since the dev
  board's defaults (GPIO9/10/11) aren't physically exposed on the XIAO.
2026-07-20 22:24:15 -04:00

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Markdown

# Hardware
## Parts
- An ESP32-C6 dev board (e.g. ESP32-C6-DevKitC-1). Needs 8MB flash --
see [`firmware/sdkconfig.defaults`](../firmware/sdkconfig.defaults) and
[`firmware/partitions.csv`](../firmware/partitions.csv) if yours differs.
- [Waveshare 7.3" E Ink Spectra 6 (E6) panel](https://www.waveshare.com/7.3inch-e-paper-hat-e.htm) --
800x480, 6-color, SPI.
- A USB cable for flashing/power.
## Wiring
The panel connects over SPI plus three control lines (data/command, reset,
busy). Defaults below match the reference build and are set in
[`firmware/components/epd7in3e/Kconfig`](../firmware/components/epd7in3e/Kconfig) --
override via `idf.py menuconfig` under **E-Paper Display (epd7in3e)
Configuration** if your wiring differs.
| Panel pin | ESP32-C6 GPIO | Kconfig option |
| --------- | ------------- | ----------------- |
| CLK | 20 | `EPD_PIN_CLK` |
| DIN | 19 | `EPD_PIN_MOSI` |
| CS | 18 | `EPD_PIN_CS` |
| DC | 9 | `EPD_PIN_DC` |
| RST | 10 | `EPD_PIN_RST` |
| BUSY | 11 | `EPD_PIN_BUSY` |
| VCC | 3.3V | -- |
| GND | GND | -- |
Optionally, three buttons, all wired the same way -- momentary push button
between the GPIO and GND, no external resistor needed (the firmware
enables each pin's internal pull-up, so it idles high and reads low when
pressed):
- **Next photo (GPIO2)**: a normal press skips immediately to the next
photo; see
[`firmware/README.md`](../firmware/README.md#skipping-to-the-next-photo).
- **Back photo (GPIO0)**: a normal press returns to the previously-shown
photo; see
[`firmware/README.md`](../firmware/README.md#going-back-to-the-previous-photo).
- **Menu / reset (GPIO1)**: one button, three actions by hold duration --
a quick press overlays a "scan to manage" QR code on the current photo
for 30 seconds; holding ~3s then releasing soft-resets the device
(config kept); holding ~15s factory-resets it (clears WiFi/server
config, reprovisions); see
[`firmware/README.md`](../firmware/README.md#managing-the-queue-soft-resetting-and-factory-resetting).
All three pins were picked because they're within GPIO 0-7 -- the only
pins the ESP32-C6 can wake from deep sleep on -- aren't strapping pins,
and aren't already used by the panel wiring above. Also, not
incidentally, GPIO 0-7 is *all* the deep-sleep-wakeup-capable pins this
chip has (`SOC_RTCIO_PIN_COUNT` is 8) -- worth knowing if you're
targeting a compact board like the Seeed XIAO ESP32-C6, which only
breaks out 3 of them (GPIO0/1/2). These three buttons were deliberately
designed to fit exactly that budget: two dedicated pins for the
actions where instant, unambiguous response matters most (next, back),
and everything else folded onto the third pin via hold duration instead
of needing its own pin.
### Wiring on the Seeed XIAO ESP32-C6
The XIAO only breaks out 11 GPIOs (0, 1, 2, 16, 17, 18, 19, 20, 21, 22,
23), so the dev-board defaults above don't fit -- DC/RST/BUSY (GPIO 9,
10, 11) aren't exposed on this board at all. Built with
[`build_for_board.sh xiao`](../firmware/README.md#building-for-the-seeed-xiao-esp32-c6-production-board),
which layers [`firmware/sdkconfig.xiao`](../firmware/sdkconfig.xiao) on
top of the dev-board defaults, remapping DC/RST/BUSY onto three of the
remaining free pins:
| Panel pin | XIAO GPIO | XIAO silkscreen label | Kconfig option |
| --------- | --------- | ---------------------- | --------------- |
| CLK | 20 | D9 | `EPD_PIN_CLK` (unchanged) |
| DIN | 19 | D8 | `EPD_PIN_MOSI` (unchanged) |
| CS | 18 | D10 | `EPD_PIN_CS` (unchanged) |
| DC | 16 | D6 | `EPD_PIN_DC` |
| RST | 17 | D7 | `EPD_PIN_RST` |
| BUSY | 21 | D3 | `EPD_PIN_BUSY` |
| VCC | 3.3V | 3V3 | -- |
| GND | GND | GND | -- |
The XIAO's silkscreen labels its pins D0-D10, not raw GPIO numbers --
the table above gives both.
Buttons (unchanged from the table above -- the XIAO's only three
ADC/deep-sleep-capable pins, GPIO 0/1/2, are exactly the ones already
used): next=GPIO2/**D2**, back=GPIO0/**D0**, menu/reset=GPIO1/**D1**.
That leaves GPIO22/**D4** and GPIO23/**D5** free, e.g. for the optional
VBUS mains-sense divider described under
[Battery](#battery-optional-xiao-esp32-c6) below.
`sdkconfig.xiao` also sets `FRAME_XIAO_ANTENNA_INIT=y`, which powers
the XIAO's onboard RF switch and selects its ceramic antenna at boot
(GPIO3/14, internal to the board -- not part of the wiring above).
Without it, WiFi doesn't reliably work on this board at all: the radio
comes up and logs look normal (e.g. the softAP starts and prints its
SSID/password) but the switch's control pins are left floating, so
nothing actually reaches the antenna -- the AP never becomes visible to
a scan, and a station connection would fail to associate the same way.
Seeed's own Arduino board package does this automatically; plain
ESP-IDF (what this firmware uses) doesn't, hence the explicit init.
A couple of things worth knowing if you pick different pins:
- **Avoid the ESP32-C6's strapping pins** (GPIO 4, 5, 8, 9, 15) and the
USB-JTAG pins (12, 13) where possible -- strapping pins are sampled at
reset to select boot mode. The reference wiring above already uses
GPIO9 for DC, which *is* a strapping pin; it's only sampled during
power-on/reset, so it's safe once the app is running, but if
flashing/boot ever misbehaves on your board, check whether the panel is
pulling that line low during reset.
- The panel's SPI interface is rated well above the firmware's default
4MHz clock (`EPD_SPI_CLOCK_HZ`), but breadboard/dupont-wire connections
are often unreliable much past a few MHz. Raise it once your physical
wiring is confirmed solid.
## Battery (optional, XIAO ESP32-C6)
For a battery-powered build on the Seeed XIAO ESP32-C6 (which has
BAT+/BAT- charge pads on its underside and charges over USB-C):
- A 1S 3.7V LiPo **with an integrated protection circuit** (the board
does no low-voltage cutoff of its own), soldered or JST-PH-pigtailed
to the BAT pads. JST-PH polarity is not standardized -- verify with a
multimeter before connecting.
- Battery level sense: 2x200k divider from BAT+ to GND, midpoint to
GPIO0/A0 (shared with the back button -- deliberate, see
[`firmware/README.md`](../firmware/README.md#battery-xiao-esp32-c6)).
- Optional mains detection: 2x100k divider from the 5V pin to GND,
midpoint to a spare GPIO (e.g. 22).
Both features are off by default in firmware
(`FRAME_BATTERY_ADC_GPIO`/`FRAME_VBUS_SENSE_GPIO` = -1).
## Power
The device spends nearly all its time in deep sleep, waking briefly once
an hour (configurable, see the server's web UI) to fetch and display a
photo. A full-color refresh on this panel takes 15-30+ seconds and draws
more current than deep sleep by a wide margin -- expect battery life (if
not running from USB power) to be dominated by refresh frequency, not
sleep current.