make UART.write be blocking on SAMD; add timeout property

Author: dhalbert

ports/atmel-samd/common-hal/busio/UART.c

@@ -323,29 +323,23 @@ size_t common_hal_busio_uart_write(busio_uart_obj_t *self, const uint8_t *data,
     struct io_descriptor *io;
     usart_async_get_io_descriptor(usart_desc_p, &io);
 
+    // Start writing characters. This is non-blocking and will
+    // return immediately after setting up the write.
     if (io_write(io, data, len) < 0) {
         *errcode = MP_EAGAIN;
         return MP_STREAM_ERROR;
     }
 
-    // Wait until write is complete or timeout.
-    bool done = false;
-    uint64_t start_ticks = ticks_ms;
-    // Busy-wait for timeout.
-    while (ticks_ms - start_ticks < self->timeout_ms) {
-        if (usart_async_is_tx_empty(usart_desc_p)) {
-            done = true;
+    // Busy-wait until all characters transmitted.
+    struct usart_async_status async_status;
+    while (true) {
+        usart_async_get_status(usart_desc_p, &async_status);
+        if (async_status.txcnt >= len) {
             break;
         }
         RUN_BACKGROUND_TASKS;
     }
 
-    if (!done) {
-        *errcode = MP_EAGAIN;
-        return MP_STREAM_ERROR;
-    }
-
-    // All the characters got written.
     return len;
 }
 
@@ -368,6 +362,14 @@ void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrat
     self->baudrate = baudrate;
 }
 
+mp_float_t common_hal_busio_uart_get_timeout(busio_uart_obj_t *self) {
+    return (mp_float_t) (self->timeout_ms / 1000.0f);
+}
+
+void common_hal_busio_uart_set_timeout(busio_uart_obj_t *self, mp_float_t timeout) {
+    self->timeout_ms = timeout * 1000;
+}
+
 uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
     // This assignment is only here because the usart_async routines take a *const argument.
     struct usart_async_descriptor * const usart_desc_p = (struct usart_async_descriptor * const) &self->usart_desc;
@@ -383,12 +385,14 @@ void common_hal_busio_uart_clear_rx_buffer(busio_uart_obj_t *self) {
 
 }
 
+// True if there are no characters still to be written.
 bool common_hal_busio_uart_ready_to_tx(busio_uart_obj_t *self) {
     if (self->tx_pin == NO_PIN) {
         return false;
     }
     // This assignment is only here because the usart_async routines take a *const argument.
-    const struct _usart_async_device * const usart_device_p =
-        (struct _usart_async_device * const) &self->usart_desc.device;
-    return _usart_async_is_byte_sent(usart_device_p);
+    struct usart_async_descriptor * const usart_desc_p = (struct usart_async_descriptor * const) &self->usart_desc;
+    struct usart_async_status async_status;
+    usart_async_get_status(usart_desc_p, &async_status);
+    return !(async_status.flags & USART_ASYNC_STATUS_BUSY);
 }

ports/cxd56/common-hal/busio/UART.c

@@ -102,7 +102,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     self->tx_pin = tx;
     self->rx_pin = rx;
     self->baudrate = baudrate;
-    self->timeout = timeout;
+    self->timeout_us = timeout * 1000000;
 }
 
 void common_hal_busio_uart_deinit(busio_uart_obj_t *self) {
@@ -135,7 +135,7 @@ size_t common_hal_busio_uart_read(busio_uart_obj_t *self, uint8_t *data, size_t
     FD_SET(busio_uart_dev[self->number].fd, &rfds);
 
     tv.tv_sec = 0;
-    tv.tv_usec = self->timeout * 1000;
+    tv.tv_usec = self->timeout_us;
 
     retval = select(busio_uart_dev[self->number].fd + 1, &rfds, NULL, NULL, &tv);
 
@@ -172,6 +172,14 @@ void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrat
     ioctl(busio_uart_dev[self->number].fd, TCFLSH, (long unsigned int)NULL);
 }
 
+mp_float_t common_hal_busio_uart_get_timeout(busio_uart_obj_t *self) {
+    return (mp_float_t) (self->timeout / 1000000.0f);
+}
+
+void common_hal_busio_uart_set_timeout(busio_uart_obj_t *self, mp_float_t timeout) {
+    self->timeout_us = timeout * 1000000;
+}
+
 uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
     int count = 0;
 

ports/cxd56/common-hal/busio/UART.h

@@ -37,7 +37,7 @@ typedef struct {
     const mcu_pin_obj_t *tx_pin;
     const mcu_pin_obj_t *rx_pin;
     uint32_t baudrate;
-    uint32_t timeout;
+    uint32_t timeout_us;
 } busio_uart_obj_t;
 
 void busio_uart_reset(void);

ports/nrf/common-hal/busio/UART.c

@@ -265,19 +265,6 @@ size_t common_hal_busio_uart_write (busio_uart_obj_t *self, const uint8_t *data,
 
     if ( len == 0 ) return 0;
 
-    uint64_t start_ticks = ticks_ms;
-
-    // Wait for on-going transfer to complete
-    while ( nrfx_uarte_tx_in_progress(self->uarte) && (ticks_ms - start_ticks < self->timeout_ms) ) {
-        RUN_BACKGROUND_TASKS;
-    }
-
-    // Time up
-    if ( !(ticks_ms - start_ticks < self->timeout_ms) ) {
-        *errcode = MP_EAGAIN;
-        return MP_STREAM_ERROR;
-    }
-
     // EasyDMA can only access SRAM
     uint8_t * tx_buf = (uint8_t*) data;
     if ( !nrfx_is_in_ram(data) ) {
@@ -290,7 +277,8 @@ size_t common_hal_busio_uart_write (busio_uart_obj_t *self, const uint8_t *data,
     _VERIFY_ERR(*errcode);
     (*errcode) = 0;
 
-    while ( nrfx_uarte_tx_in_progress(self->uarte) && (ticks_ms - start_ticks < self->timeout_ms) ) {
+    // Wait for write to complete.
+    while ( nrfx_uarte_tx_in_progress(self->uarte) ) {
         RUN_BACKGROUND_TASKS;
     }
 
@@ -310,6 +298,14 @@ void common_hal_busio_uart_set_baudrate(busio_uart_obj_t *self, uint32_t baudrat
     nrf_uarte_baudrate_set(self->uarte->p_reg, get_nrf_baud(baudrate));
 }
 
+mp_float_t common_hal_busio_uart_get_timeout(busio_uart_obj_t *self) {
+    return (mp_float_t) (self->timeout_ms / 1000.0f);
+}
+
+void common_hal_busio_uart_set_timeout(busio_uart_obj_t *self, mp_float_t timeout) {
+    self->timeout_ms = timeout * 1000;
+}
+
 uint32_t common_hal_busio_uart_rx_characters_available(busio_uart_obj_t *self) {
     return ringbuf_count(&self->rbuf);
 }