Fix Wire register

Move TWBR register from Wire.cpp to twi.c file.

2 files changed, 17 insertions, 0 deletions

diff --git a/libraries/Wire/src/utility/twi.c b/libraries/Wire/src/utility/twi.c
index 7efcc5a..f5d7d5b 100644
--- a/libraries/Wire/src/utility/twi.c
+++ b/libraries/Wire/src/utility/twi.c
@@ -119,6 +119,22 @@ void twi_setAddress(uint8_t address)
 }
 
 /* 
+ * Function twi_setClock
+ * Desc     sets twi bit rate
+ * Input    Clock Frequency
+ * Output   none
+ */
+void twi_setFrequency(uint32_t frequency)
+{
+  TWBR = ((F_CPU / frequency) - 16) / 2;
+  
+  /* twi bit rate formula from atmega128 manual pg 204
+  SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
+  note: TWBR should be 10 or higher for master mode
+  It is 72 for a 16mhz Wiring board with 100kHz TWI */
+}
+
+/* 
  * Function twi_readFrom
  * Desc     attempts to become twi bus master and read a
  *          series of bytes from a device on the bus
diff --git a/libraries/Wire/src/utility/twi.h b/libraries/Wire/src/utility/twi.h
index 4c52bc5..d27325e 100644
--- a/libraries/Wire/src/utility/twi.h
+++ b/libraries/Wire/src/utility/twi.h
@@ -41,6 +41,7 @@
   void twi_init(void);
   void twi_disable(void);
   void twi_setAddress(uint8_t);
+  void twi_setFrequency(uint32_t);
   uint8_t twi_readFrom(uint8_t, uint8_t*, uint8_t, uint8_t);
   uint8_t twi_writeTo(uint8_t, uint8_t*, uint8_t, uint8_t, uint8_t);
   uint8_t twi_transmit(const uint8_t*, uint8_t);