Initial Release

pio/uart_rx/uart_rx.c

@@ -0,0 +1,60 @@
+/**
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdio.h>
+
+#include "pico/stdlib.h"
+#include "pico/multicore.h"
+#include "hardware/pio.h"
+#include "hardware/uart.h"
+#include "uart_rx.pio.h"
+
+// This program
+// - Uses UART1 (the spare UART, by default) to transmit some text
+// - Uses a PIO state machine to receive that text
+// - Prints out the received text to the default console (UART0)
+// This might require some reconfiguration on boards where UART1 is the
+// default UART.
+
+#define SERIAL_BAUD PICO_DEFAULT_UART_BAUD_RATE
+#define HARD_UART_INST uart1
+
+// You'll need a wire from GPIO4 -> GPIO3
+#define HARD_UART_TX_PIN 4
+#define PIO_RX_PIN 3
+
+// Ask core 1 to print a string, to make things easier on core 0
+void core1_main() {
+    const char *s = (const char *) multicore_fifo_pop_blocking();
+    uart_puts(HARD_UART_INST, s);
+}
+
+int main() {
+    // Console output (also a UART, yes it's confusing)
+    setup_default_uart();
+    printf("Starting PIO UART RX example\n");
+
+    // Set up the hard UART we're going to use to print characters
+    uart_init(HARD_UART_INST, SERIAL_BAUD);
+    gpio_set_function(HARD_UART_TX_PIN, GPIO_FUNC_UART);
+
+    // Set up the state machine we're going to use to receive them.
+    PIO pio = pio0;
+    uint sm = 0;
+    uint offset = pio_add_program(pio, &uart_rx_program);
+    uart_rx_program_init(pio, sm, offset, PIO_RX_PIN, SERIAL_BAUD);
+
+    // Tell core 1 to print some text to uart1 as fast as it can
+    multicore_launch_core1(core1_main);
+    const char *text = "Hello, world from PIO! (Plus 2 UARTs and 2 cores, for complex reasons)\n";
+    multicore_fifo_push_blocking((uint32_t) text);
+
+    // Echo characters received from PIO to the console
+    while (true) {
+        char c = uart_rx_program_getc(pio, sm);
+        putchar(c);
+    }
+}