X-Git-Url: https://git.friedersdorff.com/?a=blobdiff_plain;f=keyboard%2Fergodox%2Ftwimaster.c;h=3f9ccb3c0737ac4d43697dc639db5bd8076f8190;hb=HEAD;hp=f91c08e6e4e83ccd0fc570848d82845a43b0c9f5;hpb=57c6b597ead6a98ddaade97d66de55928a4fb2a2;p=max%2Ftmk_keyboard.git

diff --git a/keyboard/ergodox/twimaster.c b/keyboard/ergodox/twimaster.c
index f91c08e6..3f9ccb3c 100644
--- a/keyboard/ergodox/twimaster.c
+++ b/keyboard/ergodox/twimaster.c
@@ -1,7 +1,7 @@
 /*************************************************************************
 * Title:    I2C master library using hardware TWI interface
 * Author:   Peter Fleury <pfleury@gmx.ch>  http://jump.to/fleury
-* File:     $Id: twimaster.c,v 1.3 2005/07/02 11:14:21 Peter Exp $
+* File:     $Id: twimaster.c,v 1.4 2015/01/17 12:16:05 peter Exp $
 * Software: AVR-GCC 3.4.3 / avr-libc 1.2.3
 * Target:   any AVR device with hardware TWI 
 * Usage:    API compatible with I2C Software Library i2cmaster.h
@@ -12,13 +12,13 @@
 #include <i2cmaster.h>
 
 
-/* define CPU frequency in Mhz here if not defined in Makefile */
+/* define CPU frequency in hz here if not defined in Makefile */
 #ifndef F_CPU
-#define F_CPU 16000000UL
+#define F_CPU 4000000UL
 #endif
 
 /* I2C clock in Hz */
-#define SCL_CLOCK  400000L
+#define SCL_CLOCK  100000L
 
 
 /*************************************************************************
@@ -26,16 +26,10 @@
 *************************************************************************/
 void i2c_init(void)
 {
-  /* initialize TWI clock
-   * minimal values in Bit Rate Register (TWBR) and minimal Prescaler
-   * bits in the TWI Status Register should give us maximal possible
-   * I2C bus speed - about 444 kHz
-   *
-   * for more details, see 20.5.2 in ATmega16/32 secification
-   */
+  /* initialize TWI clock: 100 kHz clock, TWPS = 0 => prescaler = 1 */
   
-  TWSR = 0;     /* no prescaler */
-  TWBR = 10;    /* must be >= 10 for stable operation */
+  TWSR = 0;                         /* no prescaler */
+  TWBR = ((F_CPU/SCL_CLOCK)-16)/2;  /* must be > 10 for stable operation */
 
 }/* i2c_init */