For the original question, yes, non-blocking forms of all the blocking APIs are welcome.
Cheers,
Karl P
Chuck McManis <chuck.mcma...@gmail.com> wrote:
> What I do Warren is have the USART read into a FIFO, so the ISR
> just takes characters as they arrive and sticks then in a fifo
> and updates the index of where to stick the next character. The
> read function has its own index and just reads from the FIFO
> when the current and next index differ. A check for a character
> available is simply if (cur_index != next_index)
>
> --Chuck
>
> On Mon, Feb 20, 2017 at 9:21 AM, Warren Gay <ve3...@gmail.com>
> wrote:
> > I am using FreeRTOS in connection with libopencm3. Within a task however, I
> > would like to be able to query the TX or RX status prior to committing to a
> > blocking operation. However, libopencm3() only provides blocking operations,
> > which spin on the CPU.
> >
> > The following code gives the spirit of what I am trying to do:
> >
> > inline static int
> > usart_tx_ready(uint32_t usart) {
> > return (USART_SR(usart) & USART_SR_TXE) != 0;
> > }
> >
> > static void
> > uart_task(void *args) {
> > char ch;
> >
> > for (;;) {
> > /* Receive char to be TX */
> > if ( xQueueReceive(uart_txq,&ch,500) == pdPASS ) {
> > while ( !usart_tx_ready(USART1) )
> > taskYIELD(); /* Yield CPU to ready tasks */
> > usart_send_blocking(USART1,ch); /* blocking call */
> > }
> > }
> > }
> >
> > The present code has the appearance of working but using the UART register
> > directly (is there a potential ISR conflict with this?)
> >
> > Eventually, I'll want to do something similar for receiving. Ideally, this
> > would allow one thread (task) to handle both the RX and TX, to avoid thread
> > related problems.
> >
> > So it would be a welcome addition to the libopencm3 library to provide
> > routines:
> >
> > int usart_send_ready(uint32_t usart);
> > int usart_recv_ready(uint32_t usart);
> >
> > Is there any interest in this? If not, is the approach used for TX above
> > valid? Will the same approach be safe for RX? I didn't look to see if the
> > recv side was interrupt driven or not.
> >
> > Thanks, Warren
> >
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