Initial Release

pio/addition/CMakeLists.txt

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+add_executable(pio_addition)
+
+pico_generate_pio_header(pio_addition ${CMAKE_CURRENT_LIST_DIR}/addition.pio)
+
+target_sources(pio_addition PRIVATE addition.c)
+
+target_link_libraries(pio_addition PRIVATE pico_stdlib hardware_pio)
+pico_add_extra_outputs(pio_addition)
+
+# add url via pico_set_program_url
+example_auto_set_url(pio_addition)

pio/addition/addition.c

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+/**
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "pico/stdlib.h"
+#include "hardware/pio.h"
+#include "addition.pio.h"
+
+// Pop quiz: how many additions does the processor do when calling this function
+uint32_t do_addition(PIO pio, uint sm, uint32_t a, uint32_t b) {
+    pio_sm_put_blocking(pio, sm, a);
+    pio_sm_put_blocking(pio, sm, b);
+    return pio_sm_get_blocking(pio, sm);
+}
+
+int main() {
+    stdio_init_all();
+
+    PIO pio = pio0;
+    uint sm = 0;
+    uint offset = pio_add_program(pio, &addition_program);
+    addition_program_init(pio, sm, offset);
+
+    printf("Doing some random additions:\n");
+    for (int i = 0; i < 10; ++i) {
+        uint a = rand() % 100;
+        uint b = rand() % 100;
+        printf("%u + %u = %u\n", a, b, do_addition(pio, sm, a, b));
+    }
+}

pio/addition/addition.pio

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+.program addition
+
+; Pop two 32 bit integers from the TX FIFO, add them together, and push the
+; result to the TX FIFO. Autopush/pull should be disabled as we're using
+; explicit push and pull instructions.
+;
+; This program uses the two's complement identity x + y == ~(~x - y)
+
+	pull
+	mov x, ~osr
+	pull
+	mov y, osr
+	jmp test        ; this loop is equivalent to the following C code:
+incr:               ; while (y--)
+	jmp x-- test    ;     x--;
+test:               ; This has the effect of subtracting y from x, eventually.
+	jmp y-- incr
+	mov isr, ~x
+	push
+
+% c-sdk {
+static inline void addition_program_init(PIO pio, uint sm, uint offset) {
+	pio_sm_config c = addition_program_get_default_config(offset);
+	pio_sm_init(pio, sm, offset, &c);
+	pio_sm_set_enabled(pio, sm, true);
+}
+%}