dhalbert · Oct 12, 2026 · Oct 13, 2026 · Oct 13, 2026 · Oct 13, 2026 · Oct 13, 2026
diff --git a/ports/zephyr-cp/Makefile b/ports/zephyr-cp/Makefile
@@ -61,16 +61,25 @@ endif
 # When DEBUG=1, apply additional Kconfig fragments for debug-friendly settings.
 DEBUG_CONF_FILE ?= $(CURDIR)/debug.conf
 ifeq ($(DEBUG),1)
-ifneq ($(CP_BOARD_CONF),)
-CP_BOARD_CONF := $(CP_BOARD_CONF);$(DEBUG_CONF_FILE)
-else
-CP_BOARD_CONF := $(DEBUG_CONF_FILE)
+CP_BOARD_CONF := $(strip $(CP_BOARD_CONF) $(DEBUG_CONF_FILE))
+endif
+# When CONSOLE=1 (implied by DEBUG=1), apply the board's console.overlay, if it has one, and the
+# port's console.conf. Boards whose console pins are also user pins enable the Zephyr UART console
+# only then.
+CONSOLE ?= $(DEBUG)
+CP_BOARD_CONSOLE_OVERLAY :=
+ifeq ($(CONSOLE),1)
+CP_BOARD_CONSOLE_OVERLAY := $(wildcard $(CP_BOARD_DIR)/console.overlay)
+ifneq ($(CP_BOARD_CONSOLE_OVERLAY),)
+CP_BOARD_CONF := $(strip $(CP_BOARD_CONF) $(CURDIR)/console.conf)
 endif
 endif
-# Always pass the conf file, even if empty. This undoes DEBUG=1 when it's omitted on a later run.
-# Quoted because with DEBUG=1 the value is a semicolon-separated list, and an unquoted semicolon
-# would end the shell command.
+CP_BOARD_CONF := $(subst $(eval) ,;,$(CP_BOARD_CONF))
+# Always pass the conf and console overlay files, even if empty. This undoes DEBUG=1 or CONSOLE=1
+# when it's omitted on a later run. Quoted because the conf value can be a semicolon-separated
+# list, and an unquoted semicolon would end the shell command.
 WEST_CMAKE_ARGS += -Dzephyr-cp_EXTRA_CONF_FILE="$(CP_BOARD_CONF)"
+WEST_CMAKE_ARGS += -Dzephyr-cp_EXTRA_DTC_OVERLAY_FILE="$(CP_BOARD_CONSOLE_OVERLAY)"
 
 # Boards can opt into building the MCUboot bootloader (and thus BLE OTA
 # updates) by shipping a sysbuild.conf fragment. It sets sysbuild-level

diff --git a/ports/zephyr-cp/README.md b/ports/zephyr-cp/README.md
@@ -28,6 +28,12 @@ make BOARD=nordic_nrf5340dk
 This uses Zephyr's cmake to generate Makefiles that then delegate to
 `tools/cpbuild/build_circuitpython.py` to build the CircuitPython bits in parallel.
 
+`DEBUG=1` adds the debug Kconfig settings in `debug.conf`. `CONSOLE=1` (implied
+by `DEBUG=1`) applies a board's `console.overlay`, if it has one, together with
+the port's `console.conf`, which turns the Zephyr UART console back on. Boards
+whose console UART pins are also user pins, such as the Feather nRF52840, have
+the Zephyr UART console only in those builds.
+
 ## Native simulator build container
 
 Building the native sim requires `libsdl2-dev:i386` and other 32bit dependencies that

diff --git a/ports/zephyr-cp/boards/adafruit/clue_nrf52840_zephyr/board.overlay b/ports/zephyr-cp/boards/adafruit/clue_nrf52840_zephyr/board.overlay
@@ -21,6 +21,9 @@
 // constructed, and de-initializes it on release. (I2C0 is the fixed sensor
 // bus, SPI2 the fixed display bus, and QSPI the fixed external flash.)
 //
+// See "nRF serial instances" in internal-modules/iobroker/README.md for how
+// the instances are shared and allocated.
+//
 // I2C1 and SPI1 are the same peripheral instance (0x40004000), so only one
 // mode can be enabled: I2C is the more useful dynamic bus on the CLUE.
 // SPI1 is left disabled; UART1 is enabled by neither overlay because UART0

diff --git a/ports/zephyr-cp/boards/adafruit/feather_nrf52840_sense_zephyr/board.conf b/ports/zephyr-cp/boards/adafruit/feather_nrf52840_sense_zephyr/board.conf
@@ -1,5 +1,10 @@
 CONFIG_BOARD_SERIAL_BACKEND_CDC_ACM=n
 
+# No Zephyr UART console by default (see board.overlay); a CONSOLE=1 build turns
+# it back on in console.conf.
+CONFIG_UART_CONSOLE=n
+CONFIG_LOG_BACKEND_UART=n
+
 # Pin numbers are module pins (MDBT50Q-1MV2 carries the aQFN73 inside).
 # The feathers use the MDBT50Q-1MV2 module, so pin numbers are module pins.
 CONFIG_IOBROKER_PACKAGE_MDBT50Q_1MV2=y

diff --git a/ports/zephyr-cp/boards/adafruit/feather_nrf52840_sense_zephyr/board.overlay b/ports/zephyr-cp/boards/adafruit/feather_nrf52840_sense_zephyr/board.overlay
@@ -1,244 +1,7 @@
-/* Partition layout is owned by the mcuboot fork
- * (dts/adafruit/adafruit_feather_nrf52840.dtsi) and applied to this image by
- * sysbuild. This overlay only adds board/app config. */
-/ {
-	chosen {
-		zephyr,console = &uart0;
-		zephyr,shell-uart = &uart0;
-		zephyr,uart-mcumgr = &uart0;
-		zephyr,bt-mon-uart = &uart0;
-		zephyr,bt-c2h-uart = &uart0;
-	};
-};
+/* Same as the Feather nRF52840 Express, whose upstream board is the same
+ * apart from the LED pin and the SHT3XD node below. */
+#include "../feather_nrf52840_zephyr/board.overlay"
 
-&zephyr_udc0 {
-	/delete-node/ board_cdc_acm_uart;
-};
-
-// Bus instances enabled with all pins disconnected and marked
-// zephyr,deferred-init so nothing is claimed at boot: the iobroker
-// initializes and routes a device to arbitrary pins when a busio object is
-// constructed, and de-initializes it on release: I2C1, SPI2, SPI3 and UART1.
-// (The fixed I2C0 is the Stemma QT bus with the SHT31 sensor, and UART0 the
-// console. The formerly fixed SPI1 is dropped: it had no device attached and
-// its instance is the same peripheral as I2C1, so only one mode can be
-// enabled.)
-
-&pinctrl {
-	i2c1_dyn_default: i2c1_dyn_default {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(TWIM_SDA)>,
-				<NRF_PSEL_DISCONNECTED(TWIM_SCL)>;
-		};
-	};
-
-	i2c1_dyn_sleep: i2c1_dyn_sleep {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(TWIM_SDA)>,
-				<NRF_PSEL_DISCONNECTED(TWIM_SCL)>;
-		};
-	};
-
-	spi2_dyn_default: spi2_dyn_default {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(SPIM_SCK)>,
-				<NRF_PSEL_DISCONNECTED(SPIM_MOSI)>,
-				<NRF_PSEL_DISCONNECTED(SPIM_MISO)>;
-		};
-	};
-
-	spi2_dyn_sleep: spi2_dyn_sleep {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(SPIM_SCK)>,
-				<NRF_PSEL_DISCONNECTED(SPIM_MOSI)>,
-				<NRF_PSEL_DISCONNECTED(SPIM_MISO)>;
-		};
-	};
-
-	spi3_dyn_default: spi3_dyn_default {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(SPIM_SCK)>,
-				<NRF_PSEL_DISCONNECTED(SPIM_MOSI)>,
-				<NRF_PSEL_DISCONNECTED(SPIM_MISO)>;
-		};
-	};
-
-	spi3_dyn_sleep: spi3_dyn_sleep {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(SPIM_SCK)>,
-				<NRF_PSEL_DISCONNECTED(SPIM_MOSI)>,
-				<NRF_PSEL_DISCONNECTED(SPIM_MISO)>;
-		};
-	};
-
-	uart1_dyn_default: uart1_dyn_default {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(UART_TX)>,
-				<NRF_PSEL_DISCONNECTED(UART_RX)>;
-		};
-	};
-
-	uart1_dyn_sleep: uart1_dyn_sleep {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(UART_TX)>,
-				<NRF_PSEL_DISCONNECTED(UART_RX)>;
-		};
-	};
-
-	pwm0_dyn_default: pwm0_dyn_default {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(PWM_OUT0)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT1)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT2)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT3)>;
-		};
-	};
-
-	pwm0_dyn_sleep: pwm0_dyn_sleep {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(PWM_OUT0)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT1)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT2)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT3)>;
-		};
-	};
-
-	pwm1_dyn_default: pwm1_dyn_default {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(PWM_OUT0)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT1)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT2)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT3)>;
-		};
-	};
-
-	pwm1_dyn_sleep: pwm1_dyn_sleep {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(PWM_OUT0)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT1)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT2)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT3)>;
-		};
-	};
-
-	pwm2_dyn_default: pwm2_dyn_default {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(PWM_OUT0)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT1)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT2)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT3)>;
-		};
-	};
-
-	pwm2_dyn_sleep: pwm2_dyn_sleep {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(PWM_OUT0)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT1)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT2)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT3)>;
-		};
-	};
-
-	pwm3_dyn_default: pwm3_dyn_default {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(PWM_OUT0)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT1)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT2)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT3)>;
-		};
-	};
-
-	pwm3_dyn_sleep: pwm3_dyn_sleep {
-		group1 {
-			psels = <NRF_PSEL_DISCONNECTED(PWM_OUT0)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT1)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT2)>,
-				<NRF_PSEL_DISCONNECTED(PWM_OUT3)>;
-		};
-	};
-};
-
-&i2c1 {
-	status = "okay";
-	zephyr,deferred-init;
-	pinctrl-0 = <&i2c1_dyn_default>;
-	pinctrl-1 = <&i2c1_dyn_sleep>;
-	pinctrl-names = "default", "sleep";
-};
-
-// SPI1 is the same peripheral instance as I2C1, so leave it disabled.
-&spi1 {
-	status = "disabled";
-};
-
-&spi2 {
-	status = "okay";
-	zephyr,deferred-init;
-	pinctrl-0 = <&spi2_dyn_default>;
-	pinctrl-1 = <&spi2_dyn_sleep>;
-	pinctrl-names = "default", "sleep";
-};
-
-&spi3 {
-	status = "okay";
-	zephyr,deferred-init;
-	pinctrl-0 = <&spi3_dyn_default>;
-	pinctrl-1 = <&spi3_dyn_sleep>;
-	pinctrl-names = "default", "sleep";
-};
-
-&uart1 {
-	status = "okay";
-	zephyr,deferred-init;
-	current-speed = <115200>;
-	pinctrl-0 = <&uart1_dyn_default>;
-	pinctrl-1 = <&uart1_dyn_sleep>;
-	pinctrl-names = "default", "sleep";
-};
-
-&uart0 {
-    status = "okay";
-};
-
-// PWM instances, same scheme: all four outputs disconnected and deferred
-// init, so iobroker can hand an instance to neopixel_write and pwmio and
-// route its outputs at runtime.
-
-&pwm0 {
-	status = "okay";
-	zephyr,deferred-init;
-	pinctrl-0 = <&pwm0_dyn_default>;
-	pinctrl-1 = <&pwm0_dyn_sleep>;
-	pinctrl-names = "default", "sleep";
-};
-
-&pwm1 {
-	status = "okay";
-	zephyr,deferred-init;
-	pinctrl-0 = <&pwm1_dyn_default>;
-	pinctrl-1 = <&pwm1_dyn_sleep>;
-	pinctrl-names = "default", "sleep";
-};
-
-&pwm2 {
-	status = "okay";
-	zephyr,deferred-init;
-	pinctrl-0 = <&pwm2_dyn_default>;
-	pinctrl-1 = <&pwm2_dyn_sleep>;
-	pinctrl-names = "default", "sleep";
-};
-
-&pwm3 {
-	status = "okay";
-	zephyr,deferred-init;
-	pinctrl-0 = <&pwm3_dyn_default>;
-	pinctrl-1 = <&pwm3_dyn_sleep>;
-	pinctrl-names = "default", "sleep";
-};
-
-#include "../../../app.overlay"
-
-/* Enable the SAADC for analogio (AIN0..AIN7 are on P0.02..P0.05 and P0.28..P0.31). */
-&adc {
-	status = "okay";
-};
+// CircuitPython drives the SHT31 from Python, so drop the Zephyr sensor node
+// on the now dynamic I2C0.
+/delete-node/ &SHT3XD;
diff --git a/ports/zephyr-cp/boards/adafruit/feather_nrf52840_sense_zephyr/console.overlay b/ports/zephyr-cp/boards/adafruit/feather_nrf52840_sense_zephyr/console.overlay
@@ -0,0 +1,2 @@
+/* Same console setup as the Feather nRF52840 Express. */
+#include "../feather_nrf52840_zephyr/console.overlay"
diff --git a/ports/zephyr-cp/boards/adafruit/feather_nrf52840_zephyr/board.conf b/ports/zephyr-cp/boards/adafruit/feather_nrf52840_zephyr/board.conf
@@ -1,5 +1,10 @@
 CONFIG_BOARD_SERIAL_BACKEND_CDC_ACM=n
 
+# No Zephyr UART console by default (see board.overlay); a CONSOLE=1 build turns
+# it back on in console.conf.
+CONFIG_UART_CONSOLE=n
+CONFIG_LOG_BACKEND_UART=n
+
 # Pin numbers are module pins (MDBT50Q-1MV2 carries the aQFN73 inside).
 # The feathers use the MDBT50Q-1MV2 module, so pin numbers are module pins.
 CONFIG_IOBROKER_PACKAGE_MDBT50Q_1MV2=y
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		/* Same console setup as the Feather nRF52840 Express. */
		#include "../feather_nrf52840_zephyr/console.overlay"