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Make serial_putc for NRF52 non-blocking 

Busy-wait before sending a charecter instead of after. If
serial_writeable has been called first, the busy-wait loop will
be skipped.

Added initialization code to ensure NRF_UARTE_EVENT_TXDRDY is
armed correctly.
pull/8784/head
Marcus Chang 2018-11-15 08:56:33 -08:00 committed by Russ Butler
parent 4cda158e55
commit bb98ce082e
1 changed files with 47 additions and 8 deletions
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55
targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/serial_api.c
View File

@ -1085,6 +1085,37 @@ void serial_init(serial_t *obj, PinName tx, PinName rx)
if (nordic_nrf5_uart_state[instance].usage_counter == 1) {
nrf_uarte_enable(nordic_nrf5_uart_register[instance]);
/* In order to support printing with interrupts disabled serial_putc
* must busy wait on NRF_UARTE_EVENT_TXDRDY. This event cannot be set
* manually but must be set by the UARTE module after a character has
* been sent.
*
* The following code sends a dummy character into the void so that
* NRF_UARTE_EVENT_TXDRDY is correctly set.
*/
/* Ensure pins are disconnected. */
nrf_uarte_txrx_pins_set(nordic_nrf5_uart_register[instance],
NRF_UART_PSEL_DISCONNECTED,
NRF_UART_PSEL_DISCONNECTED);
/* Set maximum baud rate to minimize waiting. */
nrf_uarte_baudrate_set(nordic_nrf5_uart_register[instance],
NRF_UARTE_BAUDRATE_1000000);
/* Send character. */
nrf_uarte_tx_buffer_set(nordic_nrf5_uart_register[instance],
&nordic_nrf5_uart_state[instance].tx_data,
1);
nrf_uarte_event_clear(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_ENDTX);
nrf_uarte_task_trigger(nordic_nrf5_uart_register[instance], NRF_UARTE_TASK_STARTTX);
/* Wait until NRF_UARTE_EVENT_TXDRDY is set before proceeding. */
bool done = false;
do {
done = nrf_uarte_event_extra_check(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_TXDRDY);
} while(done == false);
}
/* Store pins in serial object. */
@ -1488,19 +1519,26 @@ void serial_putc(serial_t *obj, int character)
int instance = uart_object->instance;
nordic_nrf5_serial_configure(obj);
/* Arm Tx DMA buffer. */
nordic_nrf5_uart_state[instance].tx_data = character;
nrf_uarte_tx_buffer_set(nordic_nrf5_uart_register[instance],
&nordic_nrf5_uart_state[instance].tx_data,
1);
nrf_uarte_event_clear(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_ENDTX);
nrf_uarte_task_trigger(nordic_nrf5_uart_register[instance], NRF_UARTE_TASK_STARTTX);
/* Wait until UART is ready to send next character. */
do {
done = nrf_uarte_event_extra_check(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_TXDRDY);
} while(done == false);
nrf_uarte_event_extra_clear(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_TXDRDY);
/* Arm Tx DMA buffer. */
nordic_nrf5_uart_state[instance].tx_data = character;
nrf_uarte_tx_buffer_set(nordic_nrf5_uart_register[instance],
&nordic_nrf5_uart_state[instance].tx_data,
1);
/* Clear Tx event and enable Tx interrupts. */
nrf_uarte_event_clear(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_ENDTX);
nrf_uarte_int_enable(nordic_nrf5_uart_register[instance], NRF_UARTE_INT_ENDTX_MASK);
/* Start transfer. */
nrf_uarte_task_trigger(nordic_nrf5_uart_register[instance], NRF_UARTE_TASK_STARTTX);
}
/** Check if the serial peripheral is readable
@ -1549,7 +1587,8 @@ int serial_writable(serial_t *obj)
int instance = uart_object->instance;
return (nordic_nrf5_uart_state[instance].tx_in_progress == 0);
return ((nordic_nrf5_uart_state[instance].tx_in_progress == 0) &&
(nrf_uarte_event_extra_check(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_TXDRDY)));
}
/***