nrf/uart: Change UART driver to be non-blocking and use IRQs.

As part of this, ctrl-C is now able to interrupt a running program.

ports/nrf/modules/machine/uart.c

@@ -35,8 +35,10 @@
 #include "py/stream.h"
 #include "py/mperrno.h"
 #include "py/mphal.h"
+#include "py/ringbuf.h"
 #include "pin.h"
 #include "genhdr/pins.h"
+#include "lib/utils/interrupt_char.h"
 
 #include "uart.h"
 #include "mpconfigboard.h"
@@ -47,15 +49,25 @@
 
 #if MICROPY_PY_MACHINE_UART
 
+typedef struct _machine_hard_uart_buf_t {
+    uint8_t tx_buf[1];
+    uint8_t rx_buf[1];
+    uint8_t rx_ringbuf_array[64];
+    volatile ringbuf_t rx_ringbuf;
+} machine_hard_uart_buf_t;
+
 typedef struct _machine_hard_uart_obj_t {
     mp_obj_base_t       base;
     const nrfx_uart_t * p_uart;      // Driver instance
+    machine_hard_uart_buf_t *buf;
 } machine_hard_uart_obj_t;
 
 static const nrfx_uart_t instance0 = NRFX_UART_INSTANCE(0);
 
+STATIC machine_hard_uart_buf_t machine_hard_uart_buf[1];
+
 STATIC const machine_hard_uart_obj_t machine_hard_uart_obj[] = {
-    {{&machine_hard_uart_type}, .p_uart = &instance0},
+    {{&machine_hard_uart_type}, .p_uart = &instance0, .buf = &machine_hard_uart_buf[0]},
 };
 
 void uart_init0(void) {
@@ -70,27 +82,36 @@ STATIC int uart_find(mp_obj_t id) {
     mp_raise_ValueError("UART doesn't exist");
 }
 
-void uart_irq_handler(mp_uint_t uart_id) {
-
+STATIC void uart_event_handler(nrfx_uart_event_t const *p_event, void *p_context) {
+    machine_hard_uart_obj_t *self = p_context;
+    if (p_event->type == NRFX_UART_EVT_RX_DONE) {
+        int chr = self->buf->rx_buf[0];
+        nrfx_uart_rx(self->p_uart, &self->buf->rx_buf[0], 1);
+        #if !MICROPY_PY_BLE_NUS && MICROPY_KBD_EXCEPTION
+        if (chr == mp_interrupt_char) {
+            mp_keyboard_interrupt();
+        } else
+        #endif
+        {
+            ringbuf_put((ringbuf_t*)&self->buf->rx_ringbuf, chr);
+        }
+    }
 }
 
-bool uart_rx_any(const machine_hard_uart_obj_t *uart_obj) {
-    // TODO: uart will block for now.
-    return true;
+bool uart_rx_any(const machine_hard_uart_obj_t *self) {
+    return self->buf->rx_ringbuf.iput != self->buf->rx_ringbuf.iget;
 }
 
 int uart_rx_char(const machine_hard_uart_obj_t * self) {
-    uint8_t ch;
-    nrfx_uart_rx(self->p_uart, &ch, 1);
-    return (int)ch;
+    return ringbuf_get((ringbuf_t*)&self->buf->rx_ringbuf);
 }
 
 STATIC nrfx_err_t uart_tx_char(const machine_hard_uart_obj_t * self, int c) {
     while (nrfx_uart_tx_in_progress(self->p_uart)) {
         ;
     }
-
-    return nrfx_uart_tx(self->p_uart, (uint8_t *)&c, 1);
+    self->buf->tx_buf[0] = c;
+    return nrfx_uart_tx(self->p_uart, &self->buf->tx_buf[0], 1);
 }
 
 
@@ -181,9 +202,15 @@ STATIC mp_obj_t machine_hard_uart_make_new(const mp_obj_type_t *type, size_t n_a
     // Set context to this instance of UART
     config.p_context = (void *)self;
 
-    // Set NULL as callback function to keep it blocking
-    nrfx_uart_init(self->p_uart, &config, NULL);
+    // Initialise ring buffer
+    self->buf->rx_ringbuf.buf = self->buf->rx_ringbuf_array;
+    self->buf->rx_ringbuf.size = sizeof(self->buf->rx_ringbuf_array);
+    self->buf->rx_ringbuf.iget = 0;
+    self->buf->rx_ringbuf.iput = 0;
 
+    // Enable event callback and start asynchronous receive
+    nrfx_uart_init(self->p_uart, &config, uart_event_handler);
+    nrfx_uart_rx(self->p_uart, &self->buf->rx_buf[0], 1);
     nrfx_uart_rx_enable(self->p_uart);
 
     return MP_OBJ_FROM_PTR(self);
@@ -250,6 +277,8 @@ STATIC mp_uint_t machine_hard_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_
 
     // read the data
     for (size_t i = 0; i < size; i++) {
+        while (!uart_rx_any(self)) {
+        }
         buf[i] = uart_rx_char(self);
     }