Move MFRC522 to dedicated SPI3_HOST bus (SCK16/MOSI17/MISO13/CS26) separate from display SPI2

README.md

@@ -46,18 +46,26 @@ All code is **pure ESP-IDF v5.x (C) / FreeRTOS** — no Arduino.
 
 | Peripheral | Function | ESP32 GPIO | Notes |
 | :--- | :--- | :---: | :--- |
-| **Shared SPI** | SCK | **18** | SPI2_HOST (VSPI), 1 MHz modules |
-| | MOSI | **23** | |
-| | MISO | **19** | |
-| **MFRC522** | SDA (CS) | **5** | dedicated chip select |
-| | RST | **22** | hard reset |
-| | 3.3V / GND | — | feed from board 3.3V rail |
-| **ST7789** (7-pin) | CS | **15** | dedicated chip select |
+> **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 |
 | | RST | **4** | panel reset |
-| | SDA | **23** | shared MOSI (data) |
-| | SCL | **18** | shared SCK (clock) |
 | | VCC / GND | 3.3V / GND | panel power (no separate LED pin) |
+| **MFRC522** — SPI3_HOST | SCK | **16** | SPI3 (HSPI) clock (own bus) |
+| | MOSI | **17** | SPI3 data out |
+| | MISO | **13** | SPI3 data in |
+| | SDA (CS) | **26** | dedicated chip select |
+| | RST | **22** | hard reset |
+| | 3.3V / GND | — | feed from board 3.3V rail |
 | **EC11** | CLK | **32** | interrupt input, pull-up |
 | | DT | **33** | quadrature B |
 | | SW | **25** | button, active low, pull-up |
@@ -69,23 +77,26 @@ All code is **pure ESP-IDF v5.x (C) / FreeRTOS** — no Arduino.
 ```
         ESP32-WROOM-32
   ┌────────────────────────────┐
-  │ 3V3  18 ── SCK ──┐         │
-  │ GND  23 ── MOSI ─┼─────┐   │
-  │       19 ── MISO ─┘     │   │
-  │        5 ── SDA ───────┤ MFRC522 22 ── RST
-  │       22 ── RST ───────┤        3V3/GND
-  │       15 ── CS ────────┤ ST7789 (7-pin)
-  │        2 ── DC ────────┤   SDA <-> MOSI, SCL <-> SCK
-  │        4 ── RST ───────┤   VCC = 3V3, GND = GND
+  │ 3V3  16 ── SCK ────────┐   │
+  │ GND  17 ── MOSI ────┐  │   │
+  │       13 ── MISO ────┼──┘   │
+  │       26 ── SDA(CS) ─┘      │
+  │       22 ── RST ─┐          │
+  │       15 ── CS ──┼───────┤ ST7789 (7-pin)
+  │        2 ── DC ──┤       │   SCL = 18, SDA = 23
+  │        4 ── RST ─┘       │   VCC = 3V3, GND = GND
+  │       18 ── SCL ─────────┘
+  │       23 ── SDA ─────────  (display = SPI2)
   │       32 ── CLK ────────┤ EC11   33 ── DT  25 ── SW/GND
   │       27 ── Din ────────┤ WS2812B  (5V + GND)
   │       14 ── SIG ────────┤ Buzzer   (GND)
   └────────────────────────────┘
 ```
 
-> **7-pin ST7789 wiring recap:** connect the display's **SCL → ESP32 GPIO 18**,
-> **SDA → GPIO 23**, **CS → 15**, **DC → 2**, **RST → 4**, **VCC → 3.3V**,
-> **GND → GND**. The MFRC522 taps the same SCL/SDA lines (its own CS is GPIO 5).
+> **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.
 
 - 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.

main/hw_pins.h

@@ -11,17 +11,23 @@
 #include "hal/gpio_types.h"
 #include "driver/spi_master.h"
 
-/* Shared SPI2_HOST (VSPI) bus.
- * NOTE: on 7-pin ST7789 modules, the display labels these SDA (MOSI) and
- * SCL (SCK) - they tap the SAME shared bus as the MFRC522. */
+/* SPI2_HOST (VSPI): dedicated to the ST7789 display.
+ * On 7-pin ST7789 modules the display labels these SDA (MOSI) and
+ * SCL (SCK). */
 #define HW_SPI_HOST        (SPI2_HOST)
-#define HW_SPI_SCK_GPIO    (GPIO_NUM_18)   /* display SCL + MFRC522 SCK */
-#define HW_SPI_MOSI_GPIO   (GPIO_NUM_23)   /* display SDA + MFRC522 MOSI */
-#define HW_SPI_MISO_GPIO   (GPIO_NUM_19)   /* MFRC522 MISO only */
+#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 */
 
-/* MFRC522 RFID reader */
-#define HW_RC522_CS_GPIO   (GPIO_NUM_5)
-#define HW_RC522_RST_GPIO  (GPIO_NUM_22)
+/* MFRC522 RFID reader - OWN SPI3_HOST (HSPI) bus, separate from the display.
+ * Using a independent controller avoids any bus interference between the
+ * panel and the reader. */
+#define HW_RFID_SPI_HOST     (SPI3_HOST)
+#define HW_RFID_SCK_GPIO     (GPIO_NUM_16)
+#define HW_RFID_MOSI_GPIO    (GPIO_NUM_17)
+#define HW_RFID_MISO_GPIO    (GPIO_NUM_13)
+#define HW_RC522_CS_GPIO     (GPIO_NUM_26)
+#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). */

main/rfid_manager.c

@@ -63,10 +63,18 @@ static void on_picc_state_changed(void *arg, esp_event_base_t base, int32_t even
 
 esp_err_t rfid_manager_init(void)
 {
+    /* Dedicated SPI3_HOST (HSPI) bus for the reader - independent controller
+     * so the display (SPI2_HOST) and the RFID never share bus timing. The
+     * rc522 driver will call spi_bus_initialize() itself on this host. */
+    static spi_bus_config_t rfid_bus_cfg = {
+        .sclk_io_num = HW_RFID_SCK_GPIO,
+        .mosi_io_num = HW_RFID_MOSI_GPIO,
+        .miso_io_num = HW_RFID_MISO_GPIO,
+    };
+
     rc522_spi_config_t driver_config = {
-        .host_id = HW_SPI_HOST,
-        /* Bus already owned by spi_bus_manager: attaching as an extra device. */
-        .bus_config = NULL,
+        .host_id = HW_RFID_SPI_HOST,
+        .bus_config = &rfid_bus_cfg,
         .dev_config = {
             .spics_io_num = HW_RC522_CS_GPIO,
             .clock_speed_hz = RC522_SPI_CLK_HZ,