Detect header W25Q16 on unified RAK firmware

docs/ota_easy.md

@@ -334,6 +334,14 @@ occupied. See the
 [nRF52 QSPI guide](ota_nrf52_qspi.md#one-w25q16-wiring-for-rak4631-or-rak3401--rak13302)
 before installing either image.
 
+For a build that uses only the 2.54 mm headers, use the unified
+`RAK_4631_repeater_unified_lora_ota` or
+`RAK_3401_repeater_unified_lora_ota` image with its matching adaptive
+OTAFIX 2.4.8 bootloader. Wire `CLK` to J10 `TX1`, `DO` to J10 `RX1`, `DI` to
+J11 `IO1`, and `CS` to J11 `AIN1`; keep the `CS` pull-up and J12 power wiring.
+This gives up UART1 GPS/PPS but leaves I2C sensors and the RAK3401 radio
+available. See the [header-only wiring table](ota_nrf52_qspi.md#header-only-w25q16-wiring-for-the-unified-rak-images).
+
 ### 4. Build and check the in-place delta
 
 ```bash

docs/ota_nrf52_qspi.md

@@ -143,6 +143,30 @@ core:
 The physical flash wiring is identical, but the two application and
 bootloader pairs are not interchangeable.
 
+### Header-only W25Q16 wiring for the unified RAK images
+
+The unified RAK repeater images and matching OTAFIX 2.4.8 adaptive bootloaders
+also support a W25Q16 through the RAK19007 2.54 mm headers. This arrangement
+does not need an IO-connector interposer or underside SPI solder points:
+
+| W25Q16 breakout | RAK19007 header | nRF52840 / Arduino pin |
+| --- | --- | --- |
+| `CLK` | J10 `TX1` | P0.16 / `16` |
+| `DO` / MISO | J10 `RX1` | P0.15 / `15` |
+| `DI` / MOSI | J11 `IO1` | P0.17 / `17` |
+| `CS` | J11 `AIN1` | P0.31 / `31` |
+| `VCC` | J12 `VDD` | regulated 3.3 V |
+| `GND` | J12 `GND` | ground |
+
+Keep the approximately 10 kOhm `CS`-to-`VDD` pull-up. This mapping gives up
+the UART1 GPS and PPS pins while the flash is fitted. The unified firmware
+detects the exact `EF4015` device before GPS discovery and leaves I2C sensor
+pins `SDA` and `SCL` available. RAK4631 can still use its UART2 bridge; its
+UART1 bridge is unavailable with header flash. RAK3401 retains its 1 W radio
+and shared sensor/radio power rail. Do not substitute `SCL` for flash clock or
+use `SWCLK`, which is the debug clock. The older dedicated W25Q16 images above
+expect the WisBlock SPI connector wiring and do not use this header mapping.
+
 ## One-time prerequisite
 
 Install a QSPI-capable OTAFIX 2.4.1 preview.9 or newer bootloader for the exact

docs/ota_user_guide.md

@@ -104,6 +104,11 @@ power the flash from VBAT. The three SPI signals require underside pads or an
 IO-connector interposer; the easy J10/J11/J12 headers do not expose them. The
 flash consumes no WisBlock slot, so a supported GPS can remain in slot A.
 
+The unified RAK repeater images additionally support a header-only W25Q16
+layout, using J10 `TX1`/`RX1` and J11 `IO1`/`AIN1`. This layout needs the
+matching adaptive OTAFIX 2.4.8 bootloader and gives up UART1 GPS/PPS; I2C
+sensors remain available. See the [pin table](ota_nrf52_qspi.md#header-only-w25q16-wiring-for-the-unified-rak-images).
+
 The ordinary full-sensor `RAK_4631_repeater` image remains too large for the
 safe internal in-place update limit. Without external flash, use
 `RAK_4631_repeater_lora_ota_no_external_sensors`; it trims selected optional