platform/build_hat: Add support for LEDs.

Add a new PWM driver for the Pico and use it to control the LEDs on the
Build HAT.

Even though the LEDs are separate (not a multicolor LED), we still treat
is as a single LED to be consistent with the other hubs (i.e. so that
hub.light.on() works the same on all hubs).

Closes: pybricks/support#2477

Author: dlech

.vscode/c_cpp_properties.json

@@ -359,7 +359,8 @@
                 "-fsingle-precision-constant"
             ],
             "cStandard": "c11",
-            "intelliSenseMode": "gcc-arm"
+            "intelliSenseMode": "gcc-arm",
+            "compilerPath": "arm-none-eabi-gcc"
         },
         {
             "name": "pbio/test",

bricks/_common/sources.mk

@@ -169,6 +169,7 @@ PBIO_SRC_C = $(addprefix lib/pbio/,\
 	drv/pwm/pwm_core.c \
 	drv/pwm/pwm_ev3.c \
 	drv/pwm/pwm_lp50xx_stm32.c \
+	drv/pwm/pwm_pico.c \
 	drv/pwm/pwm_stm32_tim.c \
 	drv/pwm/pwm_test.c \
 	drv/pwm/pwm_tlc5955_stm32.c \

lib/pbio/drv/pwm/pwm_core.c

@@ -16,6 +16,7 @@
 #include "pwm_lp50xx_stm32.h"
 #include "pwm_tlc5955_stm32.h"
 #include "pwm_ev3.h"
+#include "pwm_pico.h"
 #include "pwm.h"
 
 
@@ -28,6 +29,7 @@ void pbdrv_pwm_init(void) {
     pbdrv_pwm_stm32_tim_init(pbdrv_pwm_dev);
     pbdrv_pwm_test_init(pbdrv_pwm_dev);
     pbdrv_pwm_lp50xx_stm32_init(pbdrv_pwm_dev);
+    pbdrv_pwm_pico_init(pbdrv_pwm_dev);
     pbdrv_pwm_tlc5955_stm32_init(pbdrv_pwm_dev);
     pbdrv_pwm_tiam1808_init(pbdrv_pwm_dev);
 }

lib/pbio/drv/pwm/pwm_pico.c

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2026 The Pybricks Authors
+
+#include <pbdrv/config.h>
+
+#if PBDRV_CONFIG_PWM_PICO
+
+#include <pbdrv/pwm.h>
+#include <pbdrv/gpio.h>
+#include <pbio/error.h>
+
+#include "../drv/pwm/pwm.h"
+#include "../drv/pwm/pwm_pico.h"
+#include "../../drv/led/led_pwm.h"
+
+#include "hardware/gpio.h"
+#include "hardware/pwm.h"
+
+static pbio_error_t pbdrv_pwm_pico_set_duty(pbdrv_pwm_dev_t *dev, uint32_t ch, uint32_t value) {
+    // Blue not available.
+    if (ch == PBDRV_LED_PWM_CHANNEL_INVALID) {
+        return PBIO_SUCCESS;
+    }
+
+    if (ch >= PBDRV_CONFIG_PWM_PICO_NUM_CHANNELS) {
+        return PBIO_ERROR_INVALID_ARG;
+    }
+
+    const pbdrv_pwm_pico_platform_data_t *pdata = dev->pdata;
+    const pbdrv_pwm_pico_channel_t *channel = &pdata->channels[ch];
+
+    pwm_set_gpio_level(channel->gpio, value);
+
+    return PBIO_SUCCESS;
+}
+
+static const pbdrv_pwm_driver_funcs_t pbdrv_pwm_pico_funcs = {
+    .set_duty = pbdrv_pwm_pico_set_duty,
+};
+
+void pbdrv_pwm_pico_init(pbdrv_pwm_dev_t *devs) {
+    const pbdrv_pwm_pico_platform_data_t *pdata = &pbdrv_pwm_pico_platform_data;
+
+    devs[pdata->id].funcs = &pbdrv_pwm_pico_funcs;
+    devs[pdata->id].pdata = pdata;
+
+    // Set GPIO alt modes for the PRU
+    for (int i = 0; i < PBDRV_CONFIG_PWM_PICO_NUM_CHANNELS; i++) {
+        const pbdrv_pwm_pico_channel_t *channel = &pdata->channels[i];
+
+        // Tell the LED pin that the PWM is in charge of its value.
+        gpio_set_function(channel->gpio, GPIO_FUNC_PWM);
+        // Figure out which slice we just connected to the LED pin
+        uint slice_num = pwm_gpio_to_slice_num(channel->gpio);
+
+        // Get some sensible defaults for the slice configuration. By default,
+        // the counter is allowed to wrap over its maximum range (0 to 2**16-1)
+        pwm_config config = pwm_get_default_config();
+        // Set divider, reduces counter clock to sysclock/this value
+        pwm_config_set_clkdiv(&config, 4.f);
+        // Load the configuration into our PWM slice, and set it running.
+        pwm_init(slice_num, &config, true);
+    }
+}
+
+#endif // PBDRV_CONFIG_PWM_PICO

lib/pbio/drv/pwm/pwm_pico.h

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2026 The Pybricks Authors
+
+// Hooks for unit picos.
+
+#ifndef _INTERNAL_PBDRV_PWM_PICO_H_
+#define _INTERNAL_PBDRV_PWM_PICO_H_
+
+#include <pbdrv/config.h>
+
+#if PBDRV_CONFIG_PWM_PICO
+
+#include <stdint.h>
+
+#include <pbdrv/pwm.h>
+
+/** Platform-specific device information. */
+
+typedef struct {
+    uint8_t gpio;
+} pbdrv_pwm_pico_channel_t;
+
+typedef struct {
+    uint8_t id;
+    pbdrv_pwm_pico_channel_t channels[PBDRV_CONFIG_PWM_PICO_NUM_CHANNELS];
+} pbdrv_pwm_pico_platform_data_t;
+
+// Defined in platform.c
+extern const pbdrv_pwm_pico_platform_data_t pbdrv_pwm_pico_platform_data;
+
+void pbdrv_pwm_pico_init(pbdrv_pwm_dev_t *devs);
+
+#else // PBDRV_CONFIG_PWM_PICO
+
+#define pbdrv_pwm_pico_init(dev)
+
+#endif // PBDRV_CONFIG_PWM_PICO
+
+#endif // _INTERNAL_PBDRV_PWM_PICO_H_

lib/pbio/platform/build_hat/pbdrvconfig.h

@@ -20,14 +20,18 @@
 #define PBDRV_CONFIG_IOPORT_HAS_UART                (1)
 // TODO: Implement IOPORT driver for Build HAT
 
-#define PBDRV_CONFIG_LED                            (0)
-// TODO: Implement LED driver for Build HAT (should be similar to EV3)
+#define PBDRV_CONFIG_LED                            (1)
+#define PBDRV_CONFIG_LED_NUM_DEV                    (1)
+#define PBDRV_CONFIG_LED_PWM                        (1)
+#define PBDRV_CONFIG_LED_PWM_NUM_DEV                (1)
 
 #define PBDRV_CONFIG_MOTOR_DRIVER                   (0)
 // TODO: Implement motor driver for Build HAT
 
-#define PBDRV_CONFIG_PWM                            (0)
-// TODO: Implement PWM driver for Build HAT
+#define PBDRV_CONFIG_PWM                            (1)
+#define PBDRV_CONFIG_PWM_NUM_DEV                    (1)
+#define PBDRV_CONFIG_PWM_PICO                       (1)
+#define PBDRV_CONFIG_PWM_PICO_NUM_CHANNELS          (2)
 
 #define PBDRV_CONFIG_RANDOM                         (0)
 // TODO: Implement RANDOM driver for Build HAT

lib/pbio/platform/build_hat/pbioconfig.h

@@ -6,7 +6,7 @@
 #define PBIO_CONFIG_DCMOTOR_NUM_DEV         (4)
 #define PBIO_CONFIG_DRIVEBASE_SPIKE         (0)
 #define PBIO_CONFIG_IMU                     (0) // TODO
-#define PBIO_CONFIG_LIGHT                   (0) // TODO
+#define PBIO_CONFIG_LIGHT                   (1)
 #define PBIO_CONFIG_LOGGER                  (1)
 #define PBIO_CONFIG_MOTOR_PROCESS           (1)
 #define PBIO_CONFIG_PORT                    (0) // TODO

lib/pbio/platform/build_hat/pbsysconfig.h

@@ -18,7 +18,7 @@
 #define PBSYS_CONFIG_STORAGE                        (0) // TODO ?
 #define PBSYS_CONFIG_STORAGE_NUM_SLOTS              (1)
 #define PBSYS_CONFIG_STORAGE_USER_DATA_SIZE         (128)
-#define PBSYS_CONFIG_STATUS_LIGHT                   (0) // TODO
+#define PBSYS_CONFIG_STATUS_LIGHT                   (1)
 #define PBSYS_CONFIG_STATUS_LIGHT_BATTERY           (0)
 #define PBSYS_CONFIG_STATUS_LIGHT_BLUETOOTH         (0)
 #define PBSYS_CONFIG_STATUS_LIGHT_STATE_ANIMATIONS  (1)

lib/pbio/platform/build_hat/platform.c

@@ -1,14 +1,63 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2025 The Pybricks Authors
+// Copyright (c) 2025-2026 The Pybricks Authors
 
 #include <pbdrv/gpio.h>
 
+#include "../drv/led/led_pwm.h"
+#include "../drv/pwm/pwm_pico.h"
+
 #include "hardware/gpio.h"
 
+enum {
+    PWM_DEV_0,
+};
+
+enum {
+    LED_DEV_0_STATUS,
+};
+
 const pbdrv_gpio_t pbdrv_ioport_platform_data_vcc_pin = {
     .pin = 17,
 };
 
+// LED
+
+static const pbdrv_led_pwm_platform_color_t pbdrv_led_pwm_color = {
+    .r_factor = 1000,
+    .g_factor = 1000,
+    .b_factor = 0,
+    // Tuned with scale_factor=17 so pure red/green are as close as possible
+    // to UINT16_MAX without exceeding it.
+    .r_brightness = 83,
+    .g_brightness = 83,
+    .b_brightness = 0,
+};
+
+const pbdrv_led_pwm_platform_data_t pbdrv_led_pwm_platform_data[PBDRV_CONFIG_LED_PWM_NUM_DEV] = {
+    {
+        .color = &pbdrv_led_pwm_color,
+        .id = LED_DEV_0_STATUS,
+        .r_id = PWM_DEV_0,
+        .r_ch = 0,
+        .g_id = PWM_DEV_0,
+        .g_ch = 1,
+        // Blue not available.
+        .b_id = PWM_DEV_0,
+        .b_ch = PBDRV_LED_PWM_CHANNEL_INVALID,
+        .scale_factor = 17,
+    },
+};
+
+// PWM
+
+const pbdrv_pwm_pico_platform_data_t pbdrv_pwm_pico_platform_data = {
+    .id = PWM_DEV_0,
+    .channels = {
+        { .gpio = 14 }, // LED0
+        { .gpio = 15 }, // LED1
+    }
+};
+
 int main(void) {
     extern void pbsys_main(void);
     pbsys_main();

pybricks/hubs/pb_type_buildhat.c

@@ -1,10 +1,12 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2025 The Pybricks Authors
+// Copyright (c) 2025-2026 The Pybricks Authors
 
 #include "py/mpconfig.h"
 
 #if PYBRICKS_PY_HUBS && PYBRICKS_HUB_BUILDHAT
 
+#include <pbsys/light.h>
+
 #include <pybricks/common.h>
 #include <pybricks/hubs.h>
 
@@ -13,16 +15,19 @@
 
 typedef struct _hubs_BuildHat_obj_t {
     mp_obj_base_t base;
+    mp_obj_t light;
     mp_obj_t system;
 } hubs_BuildHat_obj_t;
 
 static mp_obj_t hubs_BuildHat_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
     hubs_BuildHat_obj_t *self = mp_obj_malloc(hubs_BuildHat_obj_t, type);
+    self->light = common_ColorLight_internal_obj_new(pbsys_status_light_main);
     self->system = MP_OBJ_FROM_PTR(&pb_type_System);
     return MP_OBJ_FROM_PTR(self);
 }
 
 static const pb_attr_dict_entry_t hubs_BuildHat_attr_dict[] = {
+    PB_DEFINE_CONST_ATTR_RO(MP_QSTR_light, hubs_BuildHat_obj_t, light),
     PB_DEFINE_CONST_ATTR_RO(MP_QSTR_system, hubs_BuildHat_obj_t, system),
     PB_ATTR_DICT_SENTINEL
 };