diff options
| author | Keith Packard <keithp@keithp.com> | 2011-08-12 05:38:16 -0700 |
|---|---|---|
| committer | Keith Packard <keithp@keithp.com> | 2011-08-13 18:46:12 -0700 |
| commit | ebe2ffb29944abc4d6a35889c7b5f3d9f2871077 (patch) | |
| tree | c674520ad9da808ac52f318653088fb38c5b079f /src | |
| parent | 30abbdc7ffcfc809b4a3fc31486fe968161ea225 (diff) | |
altos: Put SPI in slower mode when talking to companion board
The AVR CPU on the other side just can't go very fast. This reduces
the SPI clock by a factor of 16, just under 200kHz. As the companion
commands are reasonably short, this shouldn't have a huge effect on
overall SPI utilization.
Signed-off-by: Keith Packard <keithp@keithp.com>
Diffstat (limited to 'src')
| -rw-r--r-- | src/ao_companion.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/src/ao_companion.c b/src/ao_companion.c index 8db3273e..556ce044 100644 --- a/src/ao_companion.c +++ b/src/ao_companion.c @@ -17,8 +17,18 @@ #include "ao.h" -#define COMPANION_SELECT() ao_spi_get_bit(COMPANION_CS) -#define COMPANION_DESELECT() ao_spi_put_bit(COMPANION_CS) +#define ao_spi_slow() (U0GCR = (UxGCR_CPOL_NEGATIVE | \ + UxGCR_CPHA_FIRST_EDGE | \ + UxGCR_ORDER_MSB | \ + (13 << UxGCR_BAUD_E_SHIFT))) + +#define ao_spi_fast() (U0GCR = (UxGCR_CPOL_NEGATIVE | \ + UxGCR_CPHA_FIRST_EDGE | \ + UxGCR_ORDER_MSB | \ + (17 << UxGCR_BAUD_E_SHIFT))) + +#define COMPANION_SELECT() do { ao_spi_get_bit(COMPANION_CS); ao_spi_slow(); } while (0) +#define COMPANION_DESELECT() do { ao_spi_fast(); ao_spi_put_bit(COMPANION_CS); } while (0) static __xdata struct ao_companion_command ao_companion_command; __xdata struct ao_companion_setup ao_companion_setup; |