diff options
| author | Keith Packard <keithp@keithp.com> | 2011-10-11 18:10:45 -0600 |
|---|---|---|
| committer | Keith Packard <keithp@keithp.com> | 2011-10-11 18:57:32 -0600 |
| commit | 3a28846d3ff8f82b0e97c211b9debf6d67ee5af5 (patch) | |
| tree | 58c5afcde285cc2b140e0fe541dfe081e9e2b8cd /src/avr/ao_spi_usart.c | |
| parent | e60c470b426b7be08a33133e7d8c94201d7e96d4 (diff) | |
altos/avr: Clear SPI receive buffer before clocking new data in
I don't know why this is necessary, but the receive buffer gets
'extra' data added somehow.
Signed-off-by: Keith Packard <keithp@keithp.com>
Diffstat (limited to 'src/avr/ao_spi_usart.c')
| -rw-r--r-- | src/avr/ao_spi_usart.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/src/avr/ao_spi_usart.c b/src/avr/ao_spi_usart.c index 1996fcd9..5ea11da6 100644 --- a/src/avr/ao_spi_usart.c +++ b/src/avr/ao_spi_usart.c @@ -43,15 +43,17 @@ ao_spi_send(void __xdata *block, uint16_t len) __reentrant /* Receive bytes over SPI. * - * This sets up tow DMA engines, one reading the data and another - * writing constant values to the SPI transmitter as that is what - * clocks the data coming in. + * Poll, sending zeros and reading data back */ void ao_spi_recv(void __xdata *block, uint16_t len) __reentrant { uint8_t *d = block; + /* Clear any pending data */ + while (UCSR1A & (1 << RXC1)) + (void) UDR1; + while (len--) { while (!(UCSR1A & (1 << UDRE1))); UDR1 = 0; |