examples/pio_blink: Add PIO blink example

examples/pio_blink/Makefile

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+APPLICATION = pio_blink
+BOARD ?= rpi-pico
+RIOTBASE ?= $(CURDIR)/../..
+# The board rpi-pico-w has no LED pin so you have to select the pin by hand with:
+# PIO_BLINK_PIN=GPIO_PIN\(x,y\) make ...
+PIO_BLINK_PIN ?= GPIO_UNDEF
+
+CFLAGS += -DPIO_BLINK_PIN=$(PIO_BLINK_PIN)
+
+FEATURES_REQUIRED += periph_pio
+
+DEVELHELP ?= 1
+QUIET ?= 1
+
+include $(RIOTBASE)/Makefile.include
+
+DIRS += $(CPU)_pio_blink
+USEMODULE += $(CPU)_pio_blink

examples/pio_blink/main.c

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+/*
+ * Copyright (C) 2023 Otto-von-Guericke-Universität Magdeburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+#include "board.h"
+#include "periph/pio.h"
+
+/* see blink.c */
+pio_program_t pio_blink_export_program(void);
+
+/* see blink.c */
+int pio_blink_write_program(pio_t pio, pio_program_t *pro);
+
+/* see blink.c */
+int pio_blink_init(pio_t pio, pio_sm_t sm, const pio_program_t *pro,
+                   gpio_t pin);
+
+int main(void)
+{
+    pio_program_t blink = pio_blink_export_program();
+    pio_t pio;
+    pio_sm_t sm;
+    if (pio_alloc_program_sm_lock_any(&pio, &sm, &blink)) {
+        puts("No PIO resources available.");
+        return 1;
+    }
+    if (pio_blink_write_program(pio, &blink)) {
+        puts("Program could not be written.");
+        return -1;
+    }
+    gpio_t blink_gpio = PIO_BLINK_PIN; /* see Makefile */
+    if (blink_gpio == GPIO_UNDEF) {
+#ifdef LED0_PIN
+        blink_gpio = LED0_PIN;
+#endif
+    }
+    if (pio_blink_init(pio, sm, &blink, blink_gpio)) {
+        puts("PIO blink initialization failed");
+        return 1;
+    }
+    pio_sm_start(pio, sm);
+    return 0;
+}

examples/pio_blink/rpx0xx_pio_blink/Makefile

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+include $(RIOTBASE)/Makefile.base
+include $(RIOTMAKE)/pio.inc.mk
+
+# Force generation of not existing pio header file
+blink.c: blink.pio.h

examples/pio_blink/rpx0xx_pio_blink/blink.c

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+/*
+ * Copyright (C) 2023 Fabian Hüßler
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+#include <errno.h>
+#include "pio/pio.h" /* this is the internal PIO header of the rpx0xx */
+#include "blink.pio.h" /* this is the auto generated header from blink.pio */
+
+/**
+ * @brief   Initialize the GPIO, which will be controlled by PIO
+ *
+ * Every PIO program should have a custom function to initialize GPIOs
+ * as required for the use case. The first (0) mapped set-pin (GPIO @p pin)
+ * is initially configured as low output pin.
+ *
+ * @param[in]       pio         PIO index of the PIO to use
+ * @param[in]       sm          PIO state machine index of the SM to use
+ * @param[in]       pin         GPIO pin to be mapped as first set-pin (base)
+ */
+static void pio_blink_init_pins(pio_t pio, pio_sm_t sm, gpio_t pin)
+{
+    pio_gpio_init_t init = {
+        .gpio_direction = PIO_GPIO_INIT_OUT(0),
+        .gpio_state = PIO_GPIO_INIT_LOW(0),
+        .gpio_base = pin,
+        .gpio_count = 1
+    };
+    pio_sm_set_set_pins_init(pio, sm, &init);
+}
+
+/**
+ * @brief   Create an unmapped blinky PIO program
+ *
+ * A PIO program needs a kind of constructor (in OOP).
+ *
+ * @return  Blinky program
+ */
+pio_program_t pio_blink_export_program(void)
+{
+    /* Call auto-generated function to retrieve a PIO program handle.
+       The program is not loaded yet. */
+    return pio_blink_create_program();
+}
+
+/**
+ * @brief   Write blink program to instruction memory
+ *
+ * A PIO program needs a function to write the instructions
+ * to the allocated program memory.
+ *
+ * @param[in]       pio         PIO index
+ * @param[in]       pro         Allocated program
+ *
+ * @return 0 on success or negative number on error
+ */
+int pio_blink_write_program(pio_t pio, pio_program_t *pro)
+{
+    pio_instr_t instr[] = PIO_BLINK_PROGRAM;
+    int ret;
+    if ((ret = pio_write_program(pio, pro, instr))) {
+        return ret;
+    }
+    return 0;
+}
+
+/**
+ * @brief   Initialize and start running a blinky PIO program from an
+ *          allocated program @p pro and PIO @p pio and locked state machine @p sm
+ *
+ * A PIO program needs a function to initialize a PIO state machine to run a program.
+ *
+ * @param[in]       pio         PIO index
+ * @param[in]       sm          PIO state machine index
+ * @param[in]       pro         Allocated program
+ * @param[in]       pin         GPIO pin to use for blinking
+ *
+ * @return  0 on successful program start or negative number on error
+ */
+int pio_blink_init(pio_t pio, pio_sm_t sm, const pio_program_t *pro,
+                   gpio_t pin)
+{
+    pio_program_conf_t conf = PIO_BLINK_PROGRAM_CONF;
+    int ret;
+    if (pin >= 32) {
+        return -ENOTSUP;
+    }
+    if ((ret = pio_sm_init_common(pio, sm, pro, &conf))) {
+        return ret;
+    }
+    pio_sm_set_clkdiv(pio, sm, pio_sm_clkdiv(2000));
+    pio_blink_init_pins(pio, sm, pin);
+    pio_sm_restart(pio, sm);
+    return 0;
+}

examples/pio_blink/rpx0xx_pio_blink/blink.pio

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+;
+; Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+;
+; SPDX-License-Identifier: BSD-3-Clause
+;
+
+.program blink
+
+.wrap_target
+begin:
+ set pins, 0    [31]
+ nop            [31]
+ nop            [31]
+ nop            [31]
+ nop            [31]
+ set pins, 1    [31]
+ nop            [31]
+ nop            [31]
+ nop            [31]
+ nop            [31]
+ jmp begin
+.wrap