Small updates to spi.md

1 files changed, 21 insertions, 12 deletions

diff --git a/doc/spi.md b/doc/spi.md
index 3237882..438d32d 100644
--- a/doc/spi.md
+++ b/doc/spi.md
@@ -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.