diff options
Diffstat (limited to 'doc/spi.md')
| -rw-r--r-- | doc/spi.md | 33 |
1 files changed, 21 insertions, 12 deletions
@@ -1,23 +1,23 @@ Serial peripheral interface --------------------------- +This interface is link to MOSI and MISO pins. Also SS pin is used when slave mode initialized. ## Functions ### spi_init ```C static inline void spi_init(enum spiMode mode) ``` -Initializes SPI interface. -Parameters: - mode - Specify mode of SPI interface - +Initializes SPI interface. +Parameters: + mode - Specify mode of SPI interface + NOTE: Global interrupt must be enabled for right function of SPI. - { SREG |= _BV(7) } ### spi_busy ```C static inline int8_t spi_busy(void) ``` -Returns NULL when device is not busy. +Returns NULL when device is not busy. When device is busy return values in non-zero. ### spi_join @@ -30,17 +30,17 @@ Blocks processor until device is not busy. ```C static inline uint8_t spi_send(uint8_t data) ``` -Swap bytes with slave over SPI. -This function blocks execution until device isn't busy (transfer completed). +Swap bytes with slave over SPI. +This function blocks execution until device isn't busy (transfer completed). WARNING: Invoke this only when interface is initialized in MASTER mode. ### spi_transfer ```C static inline void spi_transfer(uint8_t data) ``` -Transfer byte to slave over SPI. -This function isn't blocking execution until transfer is complete. -Always call spi_join before this function when called outside of spi_receive(). +Transfer byte to slave over SPI. +This function isn't blocking execution until transfer is complete. +Always call spi_join before this function when called outside of spi_receive(). WARNING: Invoke this only when interface is initialized in MASTER mode. ### spi_expose @@ -49,7 +49,7 @@ static inline void spi_expose(uint8_t data) ``` Expose data for next master request. Please don't use this when device is busy. -Best place to call this is spi_receive(). +Best place to call this is spi_receive(). WARNING: Invoke this only when interface is initialized in SLAVE mode. ## Function pointer spi_receive @@ -58,3 +58,12 @@ extern void (*spi_receive)(uint8_t data) ``` This function is called every time transfer is finished. And until return from this function interrupts are disabled. + +## Enum spiMode +```C +enum spiMode { + SPI_MODE_MASTER, + SPI_MODE_SLAVE +}; +``` +This is used as parameter for spi_init function. |