From 3a28846d3ff8f82b0e97c211b9debf6d67ee5af5 Mon Sep 17 00:00:00 2001 From: Keith Packard Date: Tue, 11 Oct 2011 18:10:45 -0600 Subject: [PATCH] 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 --- src/avr/ao_spi_usart.c | 8 +++++--- 1 file 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; -- 2.30.2