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wait for transmitter to be done before receiving

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At higher speeds, it seems we are turning off the transmitter before we
are enabling the receiver.  Unfortunately the TXEN bit in the uart mode
register is read-only, so we don't really know if the transmitter is
enabled or not.  It seems we can simply keep transmitter + reciver
running at the same time, and use the TXEMPTY bit as reliable means to
determine if we're busy transmtting.
This commit is contained in:
Harald Welte
2016-03-20 14:40:47 +01:00
parent 903d63a1e0
commit c8beefbf85
1 changed files with 20 additions and 2 deletions
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22
firmware/src_simtrace/mode_cardemu.c
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@@ -84,6 +84,19 @@ static Usart *get_usart_by_chan(uint8_t uart_chan)
* Call-Backs from card_emu.c
***********************************************************************/
static void wait_tx_idle(Usart *usart)
{
int i = 1;
/* wait until last char has been fully transmitted */
while ((usart->US_CSR & (US_CSR_TXEMPTY)) == 0) {
if (!(i%1000000)) {
TRACE_ERROR("s: %x \r\n", usart->US_CSR);
}
i++;
}
}
/* call-back from card_emu.c to enable/disable transmit and/or receive */
void card_emu_uart_enable(uint8_t uart_chan, uint8_t rxtx)
{
@@ -91,14 +104,19 @@ void card_emu_uart_enable(uint8_t uart_chan, uint8_t rxtx)
switch (rxtx) {
case ENABLE_TX:
USART_DisableIt(usart, ~US_IER_TXRDY);
USART_SetReceiverEnabled(usart, 0);
/* as irritating as it is, we actually want to keep the
* receiver enabled during transmit */
USART_SetReceiverEnabled(usart, 1);
usart->US_CR = US_CR_RSTSTA | US_CR_RSTIT | US_CR_RSTNACK;
USART_EnableIt(usart, US_IER_TXRDY);
USART_SetTransmitterEnabled(usart, 1);
break;
case ENABLE_RX:
USART_DisableIt(usart, ~US_IER_RXRDY);
USART_SetTransmitterEnabled(usart, 0);
/* as irritating as it is, we actually want to keep the
* transmitter enabled during receive */
USART_SetTransmitterEnabled(usart, 1);
wait_tx_idle(usart);
usart->US_CR = US_CR_RSTSTA | US_CR_RSTIT | US_CR_RSTNACK;
USART_EnableIt(usart, US_IER_RXRDY);
USART_SetReceiverEnabled(usart, 1);