diff --git a/src/boards/boards.c b/src/boards/boards.c
index f12e459bd..fe319760a 100644
--- a/src/boards/boards.c
+++ b/src/boards/boards.c
@@ -159,7 +159,7 @@ void board_teardown(void) {
   neopixel_teardown();
 #endif
 
-#ifdef DISPLAY_PIN_SCK
+#ifdef BOARD_HAS_DISPLAY
   board_display_teardown();
 #endif
 
@@ -238,7 +238,7 @@ static void tft_cmd(uint8_t cmd, uint8_t const* data, size_t narg) {
   tft_cs(true);
 }
 
-void board_display_init(void) {
+bool board_display_init(void) {
   //------------- SPI init -------------//
   // highspeed SPIM should set SCK and MOSI to high drive
   nrf_gpio_cfg(DISPLAY_PIN_SCK, NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_CONNECT,
@@ -277,6 +277,9 @@ void board_display_init(void) {
 #endif
 
   tft_controller_init();
+
+  // A soldered-on TFT is always present; nothing here can fail.
+  return true;
 }
 
 void board_display_teardown(void) {
@@ -928,4 +931,215 @@ static void tft_controller_init(void) {
   }
 }
 
-#endif
\ No newline at end of file
+#endif
+//--------------------------------------------------------------------+
+// Display controller - I2C mono OLED (SSD1306 / SH1106)
+//--------------------------------------------------------------------+
+// Unlike the SPI TFTs above, an I2C OLED is frequently a plug-in module
+// (the RAK1921 in a WisBlock IO slot, for instance) that may simply not be
+// fitted. Every transfer here is therefore bounded and failure-tolerant: a
+// bootloader that spins forever waiting on an absent panel is far worse
+// than one that shows no picture.
+
+#ifdef DISPLAY_PIN_SDA
+#include "nrf_twim.h"
+
+#ifndef DISPLAY_I2C_ADDR
+#define DISPLAY_I2C_ADDR      0x3C
+#endif
+
+#ifndef DISPLAY_COL_OFFSET
+// SH1106 and friends have 132 columns of GDDRAM behind a 128-column glass,
+// centred, so the visible window starts at column 2.
+#define DISPLAY_COL_OFFSET    0
+#endif
+
+// Total addressable columns, which may exceed the visible width. Only the
+// blanking pass cares: columns outside the glass still hold undefined data
+// at power-up, and on a panel whose offset is slightly off they show.
+#ifndef DISPLAY_GDDRAM_WIDTH
+#define DISPLAY_GDDRAM_WIDTH  (DISPLAY_COL_OFFSET + DISPLAY_WIDTH)
+#endif
+
+#ifndef DISPLAY_CONTRAST
+#define DISPLAY_CONTRAST      0xCF
+#endif
+
+// Milliseconds to let the panel's rail come up before we talk to it.
+#ifndef DISPLAY_POWER_ON_MS
+#define DISPLAY_POWER_ON_MS   100
+#endif
+
+// TWIM0 is the same peripheral ID as SPIM0, which the TFT path uses; boards.h
+// rejects a board.h that asks for both.
+#define _twim NRF_TWIM0
+
+// I2C control bytes: Co=0, D/C# selects the command or data stream.
+#define OLED_CTRL_CMD         0x00
+#define OLED_CTRL_DATA        0x40
+
+// Bound every wait. At 400 kHz a 129-byte page is ~2.9 ms; this is a couple
+// of orders of magnitude beyond that, so it only ever fires on a dead bus.
+#define TWI_GUARD_LOOPS       2000000UL
+
+static bool _display_present = false;
+
+static void oled_write_page(uint8_t page, uint8_t col, uint8_t const* buf, size_t nbytes);
+
+// Blocking write of a whole I2C transaction. Returns false on NACK, bus
+// error, or timeout, leaving the peripheral idle and ready for the next try.
+static bool twi_write(uint8_t const* buf, size_t len) {
+  nrf_twim_event_clear(_twim, NRF_TWIM_EVENT_STOPPED);
+  nrf_twim_event_clear(_twim, NRF_TWIM_EVENT_ERROR);
+  (void) nrf_twim_errorsrc_get_and_clear(_twim);
+
+  nrf_twim_tx_buffer_set(_twim, buf, len);
+  nrf_twim_shorts_set(_twim, NRF_TWIM_SHORT_LASTTX_STOP_MASK);
+  nrf_twim_task_trigger(_twim, NRF_TWIM_TASK_STARTTX);
+
+  uint32_t guard = TWI_GUARD_LOOPS;
+  while (!nrf_twim_event_check(_twim, NRF_TWIM_EVENT_STOPPED) &&
+         !nrf_twim_event_check(_twim, NRF_TWIM_EVENT_ERROR) &&
+         --guard) {}
+
+  bool const ok = (guard != 0) && !nrf_twim_event_check(_twim, NRF_TWIM_EVENT_ERROR);
+
+  if (!ok) {
+    // An address NACK or a stuck bus can leave the transfer half-done.
+    nrf_twim_task_trigger(_twim, NRF_TWIM_TASK_STOP);
+    guard = TWI_GUARD_LOOPS;
+    while (!nrf_twim_event_check(_twim, NRF_TWIM_EVENT_STOPPED) && --guard) {}
+    (void) nrf_twim_errorsrc_get_and_clear(_twim);
+  }
+
+  return ok;
+}
+
+// EasyDMA can only read from RAM, so command lists must live on the stack,
+// never in flash.
+static bool oled_cmds(uint8_t* buf, size_t len) {
+  buf[0] = OLED_CTRL_CMD;
+  return twi_write(buf, len);
+}
+
+bool board_display_init(void) {
+  _display_present = false;
+
+#if defined(DISPLAY_VSENSOR_PIN) && DISPLAY_VSENSOR_PIN >= 0
+  nrf_gpio_cfg_output(DISPLAY_VSENSOR_PIN);
+  nrf_gpio_pin_write(DISPLAY_VSENSOR_PIN, DISPLAY_VSENSOR_ON);
+  NRFX_DELAY_MS(DISPLAY_POWER_ON_MS);
+#endif
+
+  // Open-drain with the internal pull-ups engaged. Boards that carry their
+  // own pull-ups are unaffected; boards with an empty socket get a bus that
+  // idles high, so a missing panel NACKs cleanly instead of hanging.
+  nrf_gpio_cfg(DISPLAY_PIN_SDA, NRF_GPIO_PIN_DIR_INPUT, NRF_GPIO_PIN_INPUT_CONNECT,
+               NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_S0D1, NRF_GPIO_PIN_NOSENSE);
+  nrf_gpio_cfg(DISPLAY_PIN_SCL, NRF_GPIO_PIN_DIR_INPUT, NRF_GPIO_PIN_INPUT_CONNECT,
+               NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_S0D1, NRF_GPIO_PIN_NOSENSE);
+
+  nrf_twim_pins_set(_twim, DISPLAY_PIN_SCL, DISPLAY_PIN_SDA);
+  nrf_twim_frequency_set(_twim, NRF_TWIM_FREQ_400K);
+  nrf_twim_address_set(_twim, DISPLAY_I2C_ADDR);
+  nrf_twim_enable(_twim);
+
+  // Display-off doubles as the presence probe: if nobody ACKs the address
+  // there is no panel, and we leave the bus alone from here on.
+  uint8_t probe[] = { OLED_CTRL_CMD, 0xAE };
+  if (!oled_cmds(probe, sizeof(probe))) {
+    nrf_twim_disable(_twim);
+    return false;
+  }
+
+  uint8_t init[] = {
+      OLED_CTRL_CMD,
+      0xD5, 0x80,                       // clock divide / oscillator frequency
+      0xA8, (uint8_t)(DISPLAY_HEIGHT - 1), // multiplex ratio
+      0xD3, 0x00,                       // display offset
+      0x40,                             // start line 0
+#ifdef DISPLAY_CONTROLLER_SH1106
+      0xAD, 0x8B,                       // SH1106 DC-DC converter on
+#else
+      0x8D, 0x14,                       // SSD1306 charge pump on
+#endif
+      // Page addressing mode. Both parts support it, and it lets one
+      // draw-page routine cover the SH1106, which has no horizontal mode.
+      0x20, 0x02,
+      0xA1,                             // segment remap: column 127 -> SEG0
+      0xC8,                             // COM scan direction: reversed
+#if DISPLAY_HEIGHT >= 64
+      0xDA, 0x12,                       // COM pins: alternative, no remap
+#else
+      0xDA, 0x02,                       // COM pins: sequential, no remap
+#endif
+      0x81, DISPLAY_CONTRAST,
+      0xD9, 0xF1,                       // pre-charge period
+      0xDB, 0x40,                       // VCOMH deselect level
+      0xA4,                             // resume from RAM contents
+      0xA6,                             // non-inverted
+      0x2E,                             // scrolling off
+  };
+  if (!oled_cmds(init, sizeof(init))) {
+    nrf_twim_disable(_twim);
+    return false;
+  }
+
+  _display_present = true;
+
+  // GDDRAM contents are undefined at power-up, and the panel is still off
+  // from the probe. Blank the RAM first so switching on cannot flash noise.
+  uint8_t blank[DISPLAY_GDDRAM_WIDTH];
+  memset(blank, 0, sizeof(blank));
+  for (uint8_t page = 0; page < DISPLAY_HEIGHT / 8; ++page) {
+    oled_write_page(page, 0, blank, sizeof(blank));
+  }
+
+  // Display on. The probe above sent 0xAE; without this the panel stays
+  // dark no matter what we write to it.
+  uint8_t on[] = { OLED_CTRL_CMD, 0xAF };
+  if (!oled_cmds(on, sizeof(on))) {
+    _display_present = false;
+    nrf_twim_disable(_twim);
+    return false;
+  }
+
+  return true;
+}
+
+void board_display_teardown(void) {
+  if (_display_present) {
+    uint8_t off[] = { OLED_CTRL_CMD, 0xAE };
+    (void) oled_cmds(off, sizeof(off));
+    _display_present = false;
+  }
+  nrf_twim_disable(_twim);
+}
+
+static void oled_write_page(uint8_t page, uint8_t col, uint8_t const* buf, size_t nbytes) {
+  if (!_display_present || nbytes > DISPLAY_GDDRAM_WIDTH) return;
+
+  // Page addressing: set the page, then the low and high nibbles of the
+  // starting column, then stream the row.
+  uint8_t addr[] = {
+      OLED_CTRL_CMD,
+      (uint8_t)(0xB0 | (page & 0x0F)),
+      (uint8_t)(0x00 | (col & 0x0F)),
+      (uint8_t)(0x10 | ((col >> 4) & 0x0F)),
+  };
+  if (!oled_cmds(addr, sizeof(addr))) return;
+
+  // The control byte has to be contiguous with the pixels for EasyDMA, and
+  // the caller's buffer has no room in front of it.
+  static uint8_t page_buf[1 + DISPLAY_GDDRAM_WIDTH];
+  page_buf[0] = OLED_CTRL_DATA;
+  memcpy(page_buf + 1, buf, nbytes);
+  (void) twi_write(page_buf, nbytes + 1);
+}
+
+void board_display_draw_page(uint8_t page, uint8_t const* buf, size_t nbytes) {
+  if (nbytes > DISPLAY_WIDTH) return;
+  oled_write_page(page, DISPLAY_COL_OFFSET, buf, nbytes);
+}
+
+#endif // DISPLAY_PIN_SDA
diff --git a/src/boards/boards.h b/src/boards/boards.h
index e85f76d33..4c1d91f77 100644
--- a/src/boards/boards.h
+++ b/src/boards/boards.h
@@ -117,12 +117,38 @@ bool is_ota(void);
 //--------------------------------------------------------------------+
 // Display
 //--------------------------------------------------------------------+
-#ifdef DISPLAY_PIN_SCK
-void board_display_init(void);
+// A board opts into the DFU screens by naming a display bus in board.h:
+// DISPLAY_PIN_SCK for the SPI TFT path, DISPLAY_PIN_SDA for the I2C mono
+// path. They are mutually exclusive: TWIM0 and SPIM0 are the same
+// peripheral ID and cannot both be enabled.
+#if defined(DISPLAY_PIN_SCK) && defined(DISPLAY_PIN_SDA)
+#error "board.h defines both DISPLAY_PIN_SCK and DISPLAY_PIN_SDA - pick one display bus"
+#endif
+
+#if defined(DISPLAY_PIN_SCK) || defined(DISPLAY_PIN_SDA)
+#define BOARD_HAS_DISPLAY   1
+#endif
+
+// Mono (1bpp paged) panels vs 16-bit colour TFTs.
+#if defined(DISPLAY_CONTROLLER_SSD1306) || defined(DISPLAY_CONTROLLER_SH1106)
+#define DISPLAY_MONO        1
+#endif
+
+#ifdef BOARD_HAS_DISPLAY
+// Returns false if no panel answered, in which case nothing else here may be
+// called. Only the I2C path can fail: an OLED is a plug-in module on some
+// boards, so its absence is a normal condition, not an error.
+bool board_display_init(void);
 void board_display_teardown(void);
-void board_display_draw_line(uint16_t y, uint8_t const* buf, size_t nbytes);
 void screen_draw_drag(void);
 void screen_draw_ble(void);
+
+#ifdef DISPLAY_MONO
+// One 8-row page, DISPLAY_WIDTH bytes, LSB = topmost row of the page.
+void board_display_draw_page(uint8_t page, uint8_t const* buf, size_t nbytes);
+#else
+void board_display_draw_line(uint16_t y, uint8_t const* buf, size_t nbytes);
+#endif
 #endif
 
 //--------------------------------------------------------------------+
diff --git a/src/boards/heltec_t096/board.h b/src/boards/heltec_t096/board.h
index cf52e1ae6..62eeae709 100644
--- a/src/boards/heltec_t096/board.h
+++ b/src/boards/heltec_t096/board.h
@@ -100,6 +100,9 @@
 #define BLE_OTA_Y             38
 #define DRAG 34
 #define DRAGX 4
+// Three 32px icons have to fit in 160px: the default pendriveLogo_X of
+// 129 puts the last one at x=133..164, off the right edge of the panel.
+#define pendriveLogo_X        124
 
 //--------------------------------------------------------------------+
 // BLE OTA
diff --git a/src/boards/heltec_t1/board.h b/src/boards/heltec_t1/board.h
index a8ba1be2e..1bd71e146 100644
--- a/src/boards/heltec_t1/board.h
+++ b/src/boards/heltec_t1/board.h
@@ -99,6 +99,9 @@
 #define BLE_OTA_Y             38
 #define DRAG 34
 #define DRAGX 4
+// Three 32px icons have to fit in 160px: the default pendriveLogo_X of
+// 129 puts the last one at x=133..164, off the right edge of the panel.
+#define pendriveLogo_X        124
 
 //--------------------------------------------------------------------+
 // BLE OTA
diff --git a/src/boards/promicro_nrf52840/board.h b/src/boards/promicro_nrf52840/board.h
index 2a85aaea6..3c968f264 100644
--- a/src/boards/promicro_nrf52840/board.h
+++ b/src/boards/promicro_nrf52840/board.h
@@ -44,6 +44,30 @@
 #define BUTTON_2          _PINNUM(1, 0)
 #define BUTTON_PULL       NRF_GPIO_PIN_PULLUP
 
+/*------------------------------------------------------------------*/
+/* DISPLAY - optional SSD1306/SH1106 OLED (commonly user-wired)
+ *
+ * Pins follow the default Meshtastic promicro variant. The EASYPROMICRO
+ * arrangement puts SCL on P1.06 instead; on such a board the probe simply
+ * finds nothing and the screen stays blank, which is harmless.
+ *------------------------------------------------------------------*/
+#define DISPLAY_CONTROLLER_SSD1306
+#define DISPLAY_I2C_ADDR      0x3C
+
+#define DISPLAY_PIN_SDA       _PINNUM(1, 4)
+#define DISPLAY_PIN_SCL       _PINNUM(0, 11)
+
+#define DISPLAY_WIDTH         128
+#define DISPLAY_HEIGHT        64
+// Not yet verified on hardware. Offset 0 is right for a true 128-column
+// SSD1306; a 132-column SH1106 will sit 2px left of centre, in which case set
+// DISPLAY_COL_OFFSET to 2. Blanking spans 132 either way so no uncovered
+// column can show power-up garbage.
+#define DISPLAY_COL_OFFSET    0
+#define DISPLAY_GDDRAM_WIDTH  132
+
+#define DISPLAY_TITLE         "ProMicro"
+
 //--------------------------------------------------------------------+
 // BLE OTA
 //--------------------------------------------------------------------+
diff --git a/src/boards/wio_tracker_l1/board.h b/src/boards/wio_tracker_l1/board.h
index 67670f749..ba0c566d1 100644
--- a/src/boards/wio_tracker_l1/board.h
+++ b/src/boards/wio_tracker_l1/board.h
@@ -44,6 +44,26 @@
 #define BUTTON_2              _PINNUM(0, 8)
 #define BUTTON_PULL           NRF_GPIO_PIN_PULLUP
 
+/*------------------------------------------------------------------*/
+/* DISPLAY - SSD1306 OLED (variant declares HAS_SCREEN 1, USE_SSD1306 1)
+ *------------------------------------------------------------------*/
+#define DISPLAY_CONTROLLER_SSD1306
+#define DISPLAY_I2C_ADDR      0x3C
+
+#define DISPLAY_PIN_SDA       _PINNUM(0, 9)
+#define DISPLAY_PIN_SCL       _PINNUM(0, 10)
+
+#define DISPLAY_WIDTH         128
+#define DISPLAY_HEIGHT        64
+// Not yet verified on hardware. Offset 0 is right for a true 128-column
+// SSD1306; a 132-column SH1106 will sit 2px left of centre, in which case set
+// DISPLAY_COL_OFFSET to 2. Blanking spans 132 either way so no uncovered
+// column can show power-up garbage.
+#define DISPLAY_COL_OFFSET    0
+#define DISPLAY_GDDRAM_WIDTH  132
+
+#define DISPLAY_TITLE         "TRACKER L1"
+
 //--------------------------------------------------------------------+
 // BLE OTA
 //--------------------------------------------------------------------+
diff --git a/src/boards/wiscore_rak3401/board.h b/src/boards/wiscore_rak3401/board.h
index ae5c86bee..0224b920d 100644
--- a/src/boards/wiscore_rak3401/board.h
+++ b/src/boards/wiscore_rak3401/board.h
@@ -46,6 +46,32 @@
 #define BUTTON_2              _PINNUM(0, 8)	// change default 0.0 to 0.8, add by Michael. This pin is not connected on 4631. 
 #define BUTTON_PULL           NRF_GPIO_PIN_PULLUP
 
+/*------------------------------------------------------------------*/
+/* DISPLAY - optional SSD1306 OLED on a WisBlock IO slot
+ *
+ * Pin- and rail-identical to the RAK4631; the panel is a plug-in module, so
+ * board_display_init() probes for it and a board with an empty slot behaves
+ * exactly as it did before.
+ *------------------------------------------------------------------*/
+#define DISPLAY_CONTROLLER_SSD1306
+#define DISPLAY_I2C_ADDR      0x3C
+
+// WB_I2C1, shared by the sensor and IO slots.
+#define DISPLAY_PIN_SDA       _PINNUM(0, 13)
+#define DISPLAY_PIN_SCL       _PINNUM(0, 14)
+
+// Switchable 3V3_S rail (WB_IO2), off out of reset.
+#define DISPLAY_VSENSOR_PIN   _PINNUM(0, 34)
+#define DISPLAY_VSENSOR_ON    1
+
+#define DISPLAY_WIDTH         128
+#define DISPLAY_HEIGHT        64
+// Untested here, but the RAK4631's WisBlock OLED measured as 132-column.
+#define DISPLAY_COL_OFFSET    2
+#define DISPLAY_GDDRAM_WIDTH  132
+
+#define DISPLAY_TITLE         "RAK3401"
+
 //--------------------------------------------------------------------+
 // BLE OTA
 //--------------------------------------------------------------------+
diff --git a/src/boards/wiscore_rak4631_board/board.h b/src/boards/wiscore_rak4631_board/board.h
index 7886cc334..880d27e84 100644
--- a/src/boards/wiscore_rak4631_board/board.h
+++ b/src/boards/wiscore_rak4631_board/board.h
@@ -46,6 +46,36 @@
 #define BUTTON_2              _PINNUM(0, 8)	// change default 0.0 to 0.8, add by Michael. This pin is not connected on 4631. 
 #define BUTTON_PULL           NRF_GPIO_PIN_PULLUP
 
+/*------------------------------------------------------------------*/
+/* DISPLAY - optional SSD1306 OLED (RAK1921) on a WisBlock IO slot
+ *
+ * The panel is a plug-in module, so this is best-effort: board_display_init()
+ * probes the I2C address and reports absence rather than blocking, and a
+ * board with an empty slot behaves exactly as it did before.
+ *------------------------------------------------------------------*/
+#define DISPLAY_CONTROLLER_SSD1306
+
+// WB_I2C1, shared by the sensor and IO slots.
+#define DISPLAY_PIN_SDA       _PINNUM(0, 13)
+#define DISPLAY_PIN_SCL       _PINNUM(0, 14)
+#define DISPLAY_I2C_ADDR      0x3C
+
+// The slots are fed from the switchable 3V3_S rail (WB_IO2), which is off
+// out of reset - the bootloader has to raise it before the panel answers.
+#define DISPLAY_VSENSOR_PIN   _PINNUM(0, 34)
+#define DISPLAY_VSENSOR_ON    1
+
+#define DISPLAY_WIDTH         128
+#define DISPLAY_HEIGHT        64
+// This panel has 132 columns of GDDRAM behind 128px of glass, so the visible
+// window starts at column 2. Confirmed on hardware: with an offset of 0 the
+// image sat 2px left of the glass and the two uncovered columns on the right
+// showed power-up garbage.
+#define DISPLAY_COL_OFFSET    2
+#define DISPLAY_GDDRAM_WIDTH  132
+
+#define DISPLAY_TITLE         "RAK4631"
+
 //--------------------------------------------------------------------+
 // BLE OTA
 //--------------------------------------------------------------------+
diff --git a/src/boards/xiao_nrf52840_ble/board.h b/src/boards/xiao_nrf52840_ble/board.h
index 9f4c45e6e..4b9b9c94d 100644
--- a/src/boards/xiao_nrf52840_ble/board.h
+++ b/src/boards/xiao_nrf52840_ble/board.h
@@ -46,6 +46,30 @@
 #define BUTTON_2              _PINNUM(0, 3)
 #define BUTTON_PULL           NRF_GPIO_PIN_PULLUP
 
+/*------------------------------------------------------------------*/
+/* DISPLAY - optional SSD1306 OLED (user-wired)
+ *
+ * The XIAO variant offers three I2C pinouts depending on build flags; these
+ * are the kit default (NFC pins). On a board wired to D4/D5 or D6/D7 the
+ * probe finds nothing and the screen stays blank, which is harmless.
+ *------------------------------------------------------------------*/
+#define DISPLAY_CONTROLLER_SSD1306
+#define DISPLAY_I2C_ADDR      0x3C
+
+#define DISPLAY_PIN_SDA       _PINNUM(0, 30)
+#define DISPLAY_PIN_SCL       _PINNUM(0, 31)
+
+#define DISPLAY_WIDTH         128
+#define DISPLAY_HEIGHT        64
+// Not yet verified on hardware. Offset 0 is right for a true 128-column
+// SSD1306; a 132-column SH1106 will sit 2px left of centre, in which case set
+// DISPLAY_COL_OFFSET to 2. Blanking spans 132 either way so no uncovered
+// column can show power-up garbage.
+#define DISPLAY_COL_OFFSET    0
+#define DISPLAY_GDDRAM_WIDTH  132
+
+#define DISPLAY_TITLE         "XIAO"
+
 //--------------------------------------------------------------------+
 // BLE OTA
 //--------------------------------------------------------------------+
diff --git a/src/boards/xiao_nrf52840_ble_sense/board.h b/src/boards/xiao_nrf52840_ble_sense/board.h
index e512c1b78..408bf2576 100644
--- a/src/boards/xiao_nrf52840_ble_sense/board.h
+++ b/src/boards/xiao_nrf52840_ble_sense/board.h
@@ -46,6 +46,30 @@
 #define BUTTON_2              _PINNUM(0, 3)
 #define BUTTON_PULL           NRF_GPIO_PIN_PULLUP
 
+/*------------------------------------------------------------------*/
+/* DISPLAY - optional SSD1306 OLED (user-wired)
+ *
+ * The XIAO variant offers three I2C pinouts depending on build flags; these
+ * are the kit default (NFC pins). On a board wired to D4/D5 or D6/D7 the
+ * probe finds nothing and the screen stays blank, which is harmless.
+ *------------------------------------------------------------------*/
+#define DISPLAY_CONTROLLER_SSD1306
+#define DISPLAY_I2C_ADDR      0x3C
+
+#define DISPLAY_PIN_SDA       _PINNUM(0, 30)
+#define DISPLAY_PIN_SCL       _PINNUM(0, 31)
+
+#define DISPLAY_WIDTH         128
+#define DISPLAY_HEIGHT        64
+// Not yet verified on hardware. Offset 0 is right for a true 128-column
+// SSD1306; a 132-column SH1106 will sit 2px left of centre, in which case set
+// DISPLAY_COL_OFFSET to 2. Blanking spans 132 either way so no uncovered
+// column can show power-up garbage.
+#define DISPLAY_COL_OFFSET    0
+#define DISPLAY_GDDRAM_WIDTH  132
+
+#define DISPLAY_TITLE         "XIAO Sense"
+
 //--------------------------------------------------------------------+
 // BLE OTA
 //--------------------------------------------------------------------+
diff --git a/src/images.c b/src/images.c
index 2f2767fdf..a634f2b2c 100644
--- a/src/images.c
+++ b/src/images.c
@@ -1,6 +1,6 @@
 #include "boards.h"
 
-#if defined(DISPLAY_PIN_SCK)
+#ifdef BOARD_HAS_DISPLAY
 
 #include <stdint.h>
 
diff --git a/src/main.c b/src/main.c
index bd9971379..3c8f5a41e 100644
--- a/src/main.c
+++ b/src/main.c
@@ -293,9 +293,10 @@ static void check_dfu_mode(void) {
   // Enter DFU mode accordingly to input
   if (dfu_start || !valid_app) {
     if (_ota_dfu) {
-      #ifdef DISPLAY_PIN_SCK
-        board_display_init();
-        screen_draw_ble();
+      #ifdef BOARD_HAS_DISPLAY
+        if (board_display_init()) {
+          screen_draw_ble();
+        }
       #endif
       led_state(STATE_BLE_DISCONNECTED);
       if (!_sd_inited) mbr_init_sd();
diff --git a/src/screen.c b/src/screen.c
index a1f82e44f..fb637997b 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -24,7 +24,58 @@
 
 #include "boards.h"
 
-#if defined(DISPLAY_PIN_SCK)
+#ifdef BOARD_HAS_DISPLAY
+
+// Defaults for 1bpp mono panels. The stock geometry below is sized for a
+// 240x135 TFT and does not fit a typical 128x64 OLED, so give mono boards a
+// four-line layout (title / mode / version / banner) out of the box. A board
+// only has to declare its bus and title; anything here can still be
+// overridden per board.
+#ifdef DISPLAY_MONO
+#if DISPLAY_HEIGHT < 96
+// Three 32x32 icons need 96x32; that plus four text lines does not fit.
+#define DISPLAY_NO_DRAG_ICONS
+#define NOLABELS
+#endif
+
+#ifndef FONT_SIZE_LARGE
+#define FONT_SIZE_LARGE      2
+#endif
+#ifndef BANNER_TEXT
+#define BANNER_TEXT          "meshtastic.org"
+#endif
+
+// The colour bars are dark in mono, so bar 1 simply spans the panel and the
+// other two collapse; this also keeps drawBar inside the frame buffer.
+#ifndef SCREEN_BAR1_Y
+#define SCREEN_BAR1_Y        0
+#endif
+#ifndef SCREEN_BAR1_H
+#define SCREEN_BAR1_H        DISPLAY_HEIGHT
+#endif
+#ifndef SCREEN_BAR2_H
+#define SCREEN_BAR2_H        0
+#endif
+#ifndef SCREEN_BAR3_H
+#define SCREEN_BAR3_H        0
+#endif
+
+#ifndef DISPLAY_TITLE_Y
+#define DISPLAY_TITLE_Y      0
+#endif
+#ifndef DRAG_TEXT_Y
+#define DRAG_TEXT_Y          22
+#endif
+#ifndef BLE_OTA_Y
+#define BLE_OTA_Y            22
+#endif
+#ifndef UF2_VERSION_BASE_Y
+#define UF2_VERSION_BASE_Y   44
+#endif
+#ifndef BANNER_TEXT_Y
+#define BANNER_TEXT_Y        55
+#endif
+#endif // DISPLAY_MONO
 
 #ifndef BANNER_TEXT
 #define BANNER_TEXT "meshtastic.org - OTAFIX by oltaco"
@@ -121,6 +172,13 @@ const uint16_t palette[] = {
 #ifndef BLE_OTA_Y
 #define BLE_OTA_Y            65
 #endif
+// Mode line on the drag screen, for panels too short for the 32px icon row.
+#ifndef DRAG_TEXT_Y
+#define DRAG_TEXT_Y          BLE_OTA_Y
+#endif
+#ifndef DRAG_TEXT
+#define DRAG_TEXT            "USB UF2"
+#endif
 #ifndef FONT_SIZE_LARGE
 #define FONT_SIZE_LARGE      4
 #endif
@@ -129,6 +187,11 @@ const uint16_t palette[] = {
 // TODO only buffer partial screen to save SRAM
 // ESP32s2 can only statically allocated DRAM up to 160KB.
 // the remaining 160KB can only be allocated at runtime as heap.
+#ifdef DISPLAY_MONO
+_Static_assert(DISPLAY_HEIGHT % 8 == 0,
+               "mono panels are addressed in 8-row pages; DISPLAY_HEIGHT must be a multiple of 8");
+#endif
+
 static uint8_t frame_buf[DISPLAY_WIDTH * DISPLAY_HEIGHT];
 //static uint8_t* frame_buf;
 
@@ -155,12 +218,19 @@ static void printch(int x, int y, int color, const uint8_t* fnt, int size) {
   }
 }
 
+#ifndef DISPLAY_NO_DRAG_ICONS
 // print icon
 static void printicon(int x, int y, int color, const uint8_t* icon) {
   int w = *icon++;
   int h = *icon++;
   int sz = *icon++;
 
+  // The decode loop below writes w*h bytes straight into frame_buf with no
+  // clipping of its own, so anything that would land outside is dropped.
+  if (x < 0 || y < 0 || x + w > DISPLAY_WIDTH || y + h > DISPLAY_HEIGHT) {
+    return;
+  }
+
   uint8_t mask = 0x80;
   int runlen = 0;
   int runbit = 0;
@@ -201,6 +271,7 @@ static void printicon(int x, int y, int color, const uint8_t* icon) {
     }
   }
 }
+#endif // DISPLAY_NO_DRAG_ICONS
 
 static void print(int x, int y, int color, const char* text, int size) {
   // Glyphs are written straight into frame_buf with no bounds check of
@@ -231,6 +302,39 @@ static inline void print_centered(int y, int color, const char* text, int size)
 //
 //--------------------------------------------------------------------+
 
+#ifdef DISPLAY_MONO
+
+// One bit per pixel, so the 16-entry palette collapses to "lights a pixel or
+// does not". The layout above only ever draws foreground in white (text,
+// icons) and purple (the version string); the three background bars use
+// colours that stay dark. That is what lets the colour layout survive the
+// conversion without being redrawn for mono.
+#define MONO_LIT_MASK   ((1u << COLOR_WHITE) | (1u << COLOR_PURPLE))
+
+static void draw_screen(uint8_t const* fb) {
+  // SSD1306/SH1106 GDDRAM is paged: one byte spans 8 rows of a single
+  // column, LSB topmost. frame_buf is already column-major, so each output
+  // byte gathers 8 contiguous bytes of it.
+  for (int page = 0; page < DISPLAY_HEIGHT / 8; ++page) {
+    uint8_t line[DISPLAY_WIDTH];
+
+    for (int x = 0; x < DISPLAY_WIDTH; ++x) {
+      uint8_t const* col = fb + x * DISPLAY_HEIGHT + page * 8;
+      uint8_t bits = 0;
+      for (int bit = 0; bit < 8; ++bit) {
+        if (MONO_LIT_MASK & (1u << (col[bit] & 0xf))) {
+          bits |= (uint8_t) (1u << bit);
+        }
+      }
+      line[x] = bits;
+    }
+
+    board_display_draw_page((uint8_t) page, line, sizeof(line));
+  }
+}
+
+#else
+
 static void draw_screen(uint8_t const* fb) {
   uint8_t const* p = fb;
   for (int y = 0; y < DISPLAY_WIDTH; ++y) {
@@ -246,8 +350,23 @@ static void draw_screen(uint8_t const* fb) {
   }
 }
 
+#endif
+
 // draw color bar
 static void drawBar(int y, int h, int color) {
+  // Clamp to the panel: the default bar geometry is sized for a 240x135
+  // screen and would run off the end of a column on a shorter one.
+  if (y < 0) {
+    h += y;
+    y = 0;
+  }
+  if (y >= DISPLAY_HEIGHT || h <= 0) {
+    return;
+  }
+  if (y + h > DISPLAY_HEIGHT) {
+    h = DISPLAY_HEIGHT - y;
+  }
+
   for (int x = 0; x < DISPLAY_WIDTH; ++x) {
     memset(frame_buf + x * DISPLAY_HEIGHT + y, color, h);
   }
@@ -264,6 +383,12 @@ void screen_draw_drag(void) {
   print_centered(UF2_VERSION_BASE_Y, COLOR_PURPLE, UF2_VERSION_BASE, 1);
   print_centered(BANNER_TEXT_Y, COLOR_WHITE, BANNER_TEXT, 1);
 
+#ifdef DISPLAY_NO_DRAG_ICONS
+  // The icon row is three 32x32 glyphs, 96px wide and 32px tall before any
+  // spacing. A 128x64 panel cannot carry that and the four text lines, so
+  // name the mode instead.
+  print_centered(DRAG_TEXT_Y, COLOR_WHITE, DRAG_TEXT, FONT_SIZE_LARGE);
+#else
 #ifndef DRAG
 #define DRAG 70
 #endif
@@ -277,6 +402,7 @@ void screen_draw_drag(void) {
   print(22, DRAG - 12, COLOR_WHITE, "firmware.uf2", 1);
   print(160, DRAG - 12, COLOR_WHITE, UF2_VOLUME_LABEL, 1);
   #endif // NOLABELS
+#endif // DISPLAY_NO_DRAG_ICONS
 
   draw_screen(frame_buf);
 }
diff --git a/src/usb/usb.c b/src/usb/usb.c
index 30d91c0d4..5fa008077 100644
--- a/src/usb/usb.c
+++ b/src/usb/usb.c
@@ -97,9 +97,10 @@ void usb_init(bool cdc_only) {
   uf2_init();
   tusb_init();
 
-  #ifdef DISPLAY_PIN_SCK
-  board_display_init();
-  screen_draw_drag();
+  #ifdef BOARD_HAS_DISPLAY
+  if (board_display_init()) {
+    screen_draw_drag();
+  }
   #endif
 }