Move display CS/DC off strapping pins (CS=21, DC=19) so flashing works with display connected

README.md

@@ -44,20 +44,16 @@ All code is **pure ESP-IDF v5.x (C) / FreeRTOS** — no Arduino.
 
 ### Pin map
 
-| Peripheral | Function | ESP32 GPIO | Notes |
-| :--- | :--- | :---: | :--- |
 > **Display and reader are on two separate SPI controllers:** the ST7789 on
 > **SPI2_HOST (VSPI)**, the MFRC522 on **SPI3_HOST (HSPI)** — so the panel and
 > the RFID reader never share bus timing.
 
-### Pin map
-
 | Peripheral | Function | ESP32 GPIO | Notes |
 | :--- | :--- | :---: | :--- |
 | **ST7789** (7-pin) — SPI2_HOST | SCL | **18** | SPI2 (VSPI) clock |
 | | SDA | **23** | SPI2 MOSI (data) |
-| | CS | **15** | dedicated chip select |
-| | DC | **2** | data/command |
+| | CS | **21** | dedicated chip select (non-strapping pin) |
+| | DC | **19** | data/command (non-strapping pin) |
 | | RST | **4** | panel reset |
 | | VCC / GND | 3.3V / GND | panel power (no separate LED pin) |
 | **MFRC522** — SPI3_HOST | SCK | **16** | SPI3 (HSPI) clock (own bus) |
@@ -82,8 +78,8 @@ All code is **pure ESP-IDF v5.x (C) / FreeRTOS** — no Arduino.
   │       13 ── MISO ────┼──┘   │
   │       26 ── SDA(CS) ─┘      │
   │       22 ── RST ─┐          │
-  │       15 ── CS ──┼───────┤ ST7789 (7-pin)
-  │        2 ── DC ──┤       │   SCL = 18, SDA = 23
+  │       21 ── CS ──┼───────┤ ST7789 (7-pin)
+  │       19 ── DC ──┤       │   SCL = 18, SDA = 23
   │        4 ── RST ─┘       │   VCC = 3V3, GND = GND
   │       18 ── SCL ─────────┘
   │       23 ── SDA ─────────  (display = SPI2)
@@ -96,7 +92,11 @@ All code is **pure ESP-IDF v5.x (C) / FreeRTOS** — no Arduino.
 > **MFRC522 (own SPI3/HSPI bus):** SCK→16, MOSI→17, MISO→13, SDA(CS)→26,
 > RST→22, VCC→3.3V, GND→GND. It shares **no lines** with the display.
 >
-> **ST7789 (SPI2/VSPI):** SCL→18, SDA→23, CS→15, DC→2, RST→4, VCC→3.3V, GND→GND.
+> **ST7789 (SPI2/VSPI):** SCL→18, SDA→23, CS→21, DC→19, RST→4, VCC→3.3V, GND→GND.
+>
+> CS (GPIO21) and DC (GPIO19) are deliberately **not** strapping pins, so the
+> panel can stay connected during `idf.py flash`. (The old GPIO15/GPIO2
+> assignment made the panel hold boot-strap lines and block flashing.)
 
 - Keep SPI signal runs short (< 10 cm) for reliable 20 MHz display transfers.
 - NTAG213/215 FPC stickers need to sit flat and close to the MFRC522 antenna.
@@ -319,12 +319,12 @@ time (`littlefs_create_partition_image`), so a fresh flash already contains
 | Display = black / garbage | Check CS/DC/RST wiring; try toggling `esp_lcd_panel_invert_color` and `LCD_RGB_ELEMENT_ORDER_*` in `display_manager.c` |
 | Colors inverted | Same toggle as above — panel clones differ |
 | No UID printed on scan | Verify MFRC522 wiring, tag type (ISO14443A), antenna positioning; confirm `rfid: RC522 polling task pinned to Core 0` in the log |
-| Boot log: `rc522: FIFO length missmatch` / `RTOS: RFID unavailable` | Reader self-test failed. Check the MFRC522 has 3.3V power (many clones have a separate power pin), CS=GPIO5 / RST=GPIO22, and SCK/MOSI/MISO=18/23/19. Try lowering `RC522_SPI_CLK_HZ` in `rfid_manager.c` (e.g. `2000000`); some clones need a slower clock on a shared bus |
+| Boot log: `rc522: FIFO length missmatch` / `RTOS: RFID unavailable` | Reader self-test failed. Check the MFRC522 has 3.3V power (many clones have a separate power pin), CS=GPIO26 / RST=GPIO22, SCK/MOSI/MISO=16/17/13 on its own SPI3 bus. Try lowering `RC522_SPI_CLK_HZ` in `rfid_manager.c` (e.g. `1000000`); the skip-self-test option (`CONFIG_MTG_RFID_SKIP_SELFTEST`) lets scanning start anyway |
 | Wi-Fi never connects | Re-run `idf.py menuconfig`, confirm you replaced the `YOUR_...` placeholders |
 | Scryfall autocomplete shows nothing | The AP has no internet passthrough — the phone needs its own mobile data connection, or type the card name manually |
 | Can't reach 192.168.4.1 | Ensure your phone joined `MTG-Companion`, not a cached network |
-| Flash fails: `Serial data stream stopped` / must unplug the display to flash | Disconnect the ST7789 (or power it down) during `idf.py flash`: this board's display shares strapping pins GPIO2/GPIO15 and the panel can pull the 3.3V rail / strap pins at reset, corrupting the serial link mid-write. Flash, then reconnect the display. |
-| RFID step of boot log: `Buffers content missmatch`, buffer2 = `13 33 37` | The reader now answers (SPI OK) but glitches on the write/read race. `RC522_SPI_CLK_HZ` is already 2 MHz; lower further to `1000000` in `rfid_manager.c`, or check the MFRC522's separate power header gets a clean 3.3V and confirm MISO=GPIO19 is actually connected |
+| Flash fails: `Serial data stream stopped` | If the ST7789 is wired with CS=GPIO15 / DC=GPIO2 (the old strap-pin assignment), disconnect/power-down the display during `idf.py flash` — the panel holds the boot-strap lines at reset and corrupts the serial link. With the current recommended wiring (CS=GPIO21, DC=GPIO19, both non-strapping) the display can stay connected. |
+| RFID step of boot log: `Buffers content missmatch`, buffer2 = `13 33 37` | The reader answers (SPI OK) but the PCD self-test is flaky on clones. RST can stay unconnected (`-1`), the clock is already 1 MHz; confirm the MFRC522's dedicated power header gets a clean 3.3V and that MISO=GPIO13 is actually connected |
 | Card renders but no art | Card not cached yet — check `scryfall` log lines; art downloads are best-effort |
 | App grows near 2MB | mbedTLS + HTTP pulls are large; if needed, enable `CONFIG_MBEDTLS_CERTIFICATE_BUNDLE` (smaller) |
 

main/hw_pins.h

@@ -13,11 +13,12 @@
 
 /* SPI2_HOST (VSPI): dedicated to the ST7789 display.
  * On 7-pin ST7789 modules the display labels these SDA (MOSI) and
- * SCL (SCK). */
+ * SCL (SCK). MISO is unused (the display never reads the bus; the RFID
+ * reader lives on its own SPI3 bus). */
 #define HW_SPI_HOST        (SPI2_HOST)
 #define HW_SPI_SCK_GPIO    (GPIO_NUM_18)   /* display SCL */
 #define HW_SPI_MOSI_GPIO   (GPIO_NUM_23)   /* display SDA */
-#define HW_SPI_MISO_GPIO   (GPIO_NUM_19)   /* unused by display; kept for bus */
+#define HW_SPI_MISO_GPIO   (GPIO_NUM_NC)   /* unused */
 
 /* MFRC522 RFID reader - OWN SPI3_HOST (HSPI) bus, separate from the display.
  * Using a independent controller avoids any bus interference between the
@@ -30,9 +31,14 @@
 #define HW_RC522_RST_GPIO    (GPIO_NUM_22)
 
 /* ST7789 display - 7-pin breakout: CS / DC / RST / SDA / SCL / GND / VCC.
- * SDA and SCL share the SPI bus above (SCL=HW_SPI_SCK, SDA=HW_SPI_MOSI). */
-#define HW_LCD_CS_GPIO     (GPIO_NUM_15)
-#define HW_LCD_DC_GPIO     (GPIO_NUM_2)
+ * SDA and SCL share the SPI bus above (SCL=HW_SPI_SCK, SDA=HW_SPI_MOSI).
+ *
+ * IMPORTANT: CS and DC are on NON-STRAPPING pins (GPIO21, GPIO19) so the
+ * panel never interferes with the ESP32 boot/flash. Keeping these on
+ * GPIO15/GPIO2 (strapping pins) blocks flashing while the display is
+ * connected, because the panel holds the strap lines at reset. */
+#define HW_LCD_CS_GPIO     (GPIO_NUM_21)
+#define HW_LCD_DC_GPIO     (GPIO_NUM_19)
 #define HW_LCD_RST_GPIO    (GPIO_NUM_4)
 
 /* EC11 rotary encoder */

main/main.c

@@ -20,9 +20,9 @@ void app_main(void)
     ESP_ERROR_CHECK(spi_bus_manager_init());
     ESP_ERROR_CHECK(storage_manager_init());
 
-    /* RFID comes BEFORE the display: the panel's init traffic plus the strap
-     * load on GPIO15/GPIO2 can glitch the shared SPI bus and make the MFRC522
-     * self-test flake. Starting the reader on a quiet bus yields a clean test. */
+    /* RFID comes BEFORE the display: the reader lives on its own SPI3 bus now
+     * (display owns SPI2), but initializing it before the panel's init traffic
+     * still gives the self-test the quietest possible bus timing. */
     esp_err_t ret = rfid_manager_init();
     if (ret != ESP_OK || rfid_manager_start() != ESP_OK) {
         ESP_LOGW(TAG, "RFID unavailable (%s) - continuing without card scanning", esp_err_to_name(ret));