move embedded tutorials out of protocol tree

tutorials/esp32/uart-bridge/main/uart.c

@@ -0,0 +1,49 @@
+#include "main.h"
+#include "esp_idf_version.h"  // < 3.3 not supported, sadly
+
+int uart_close(int no) {
+  return uart_driver_delete(no);
+}
+
+int uart_open(int no, int rx, int tx, int cts, int rts, int baud) {
+  uart_config_t uart_config = {
+      .baud_rate = baud,
+      .data_bits = UART_DATA_8_BITS,
+      .parity = UART_PARITY_DISABLE,
+      .stop_bits = UART_STOP_BITS_1,
+      .flow_ctrl = cts > 0 && rts > 0 ? UART_HW_FLOWCTRL_CTS_RTS
+                   : cts > 0          ? UART_HW_FLOWCTRL_CTS
+                   : rts > 0          ? UART_HW_FLOWCTRL_RTS
+                                      : UART_HW_FLOWCTRL_DISABLE,
+  };
+  int e1 = uart_param_config(no, &uart_config);
+  int e2 = uart_set_pin(no, tx, rx, rts, cts);
+  int e3 =
+#if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 2, 5)
+      uart_driver_install(no, UART_HW_FIFO_LEN(no) * 2, UART_HW_FIFO_LEN(no) * 2, 0, NULL, 0);
+#else
+      uart_driver_install(no, UART_FIFO_LEN * 2, UART_FIFO_LEN * 2, 0, NULL, 0);
+#endif
+  MG_INFO(("%d: %d/%d/%d, %d %d %d", no, rx, tx, baud, e1, e2, e3));
+  if (e1 != ESP_OK || e2 != ESP_OK || e3 != ESP_OK) return -1;
+  return no;
+}
+
+void uart_init(int tx, int rx, int baud) {
+  uart_open(UART_NO, rx, tx, -1, -1, baud);
+}
+
+int uart_read(void *buf, size_t len) {
+  size_t x = 0;
+  int no = UART_NO;
+  if (uart_get_buffered_data_len(no, &x) != ESP_OK || x == 0) return 0;
+  int n = uart_read_bytes(no, buf, len, 10 / portTICK_PERIOD_MS);
+  MG_DEBUG(("%d bytes: [%.*s]", n, n, (char *) buf));
+  return n;
+}
+
+int uart_write(const void *buf, int len) {
+  int no = UART_NO;
+  MG_DEBUG(("%d bytes: [%.*s]", len, len, (char *) buf));
+  return uart_write_bytes(no, (const char *) buf, len);
+}