From 0c47e8b008ccb6bfbb7051a5c2e4b0031dae0fa5 Mon Sep 17 00:00:00 2001
From: Erez Zukerman <ezuk@madmimi.com>
Date: Tue, 27 Oct 2015 00:54:46 +0200
Subject: [Jack & Erez] Comments + tiny updates and cleanup

---
 keyboard/ergodox_ez/twimaster.c | 208 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 208 insertions(+)
 create mode 100644 keyboard/ergodox_ez/twimaster.c

(limited to 'keyboard/ergodox_ez/twimaster.c')

diff --git a/keyboard/ergodox_ez/twimaster.c b/keyboard/ergodox_ez/twimaster.c
new file mode 100644
index 000000000..f91c08e6e
--- /dev/null
+++ b/keyboard/ergodox_ez/twimaster.c
@@ -0,0 +1,208 @@
+/*************************************************************************
+* 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 $
+* 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
+**************************************************************************/
+#include <inttypes.h>
+#include <compat/twi.h>
+
+#include <i2cmaster.h>
+
+
+/* define CPU frequency in Mhz here if not defined in Makefile */
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
+/* I2C clock in Hz */
+#define SCL_CLOCK  400000L
+
+
+/*************************************************************************
+ Initialization of the I2C bus interface. Need to be called only once
+*************************************************************************/
+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
+   */
+  
+  TWSR = 0;     /* no prescaler */
+  TWBR = 10;    /* must be >= 10 for stable operation */
+
+}/* i2c_init */
+
+
+/*************************************************************************	
+  Issues a start condition and sends address and transfer direction.
+  return 0 = device accessible, 1= failed to access device
+*************************************************************************/
+unsigned char i2c_start(unsigned char address)
+{
+    uint8_t   twst;
+
+	// send START condition
+	TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
+
+	// wait until transmission completed
+	while(!(TWCR & (1<<TWINT)));
+
+	// check value of TWI Status Register. Mask prescaler bits.
+	twst = TW_STATUS & 0xF8;
+	if ( (twst != TW_START) && (twst != TW_REP_START)) return 1;
+
+	// send device address
+	TWDR = address;
+	TWCR = (1<<TWINT) | (1<<TWEN);
+
+	// wail until transmission completed and ACK/NACK has been received
+	while(!(TWCR & (1<<TWINT)));
+
+	// check value of TWI Status Register. Mask prescaler bits.
+	twst = TW_STATUS & 0xF8;
+	if ( (twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK) ) return 1;
+
+	return 0;
+
+}/* i2c_start */
+
+
+/*************************************************************************
+ Issues a start condition and sends address and transfer direction.
+ If device is busy, use ack polling to wait until device is ready
+ 
+ Input:   address and transfer direction of I2C device
+*************************************************************************/
+void i2c_start_wait(unsigned char address)
+{
+    uint8_t   twst;
+
+
+    while ( 1 )
+    {
+	    // send START condition
+	    TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
+    
+    	// wait until transmission completed
+    	while(!(TWCR & (1<<TWINT)));
+    
+    	// check value of TWI Status Register. Mask prescaler bits.
+    	twst = TW_STATUS & 0xF8;
+    	if ( (twst != TW_START) && (twst != TW_REP_START)) continue;
+    
+    	// send device address
+    	TWDR = address;
+    	TWCR = (1<<TWINT) | (1<<TWEN);
+    
+    	// wail until transmission completed
+    	while(!(TWCR & (1<<TWINT)));
+    
+    	// check value of TWI Status Register. Mask prescaler bits.
+    	twst = TW_STATUS & 0xF8;
+    	if ( (twst == TW_MT_SLA_NACK )||(twst ==TW_MR_DATA_NACK) ) 
+    	{    	    
+    	    /* device busy, send stop condition to terminate write operation */
+	        TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
+	        
+	        // wait until stop condition is executed and bus released
+	        while(TWCR & (1<<TWSTO));
+	        
+    	    continue;
+    	}
+    	//if( twst != TW_MT_SLA_ACK) return 1;
+    	break;
+     }
+
+}/* i2c_start_wait */
+
+
+/*************************************************************************
+ Issues a repeated start condition and sends address and transfer direction 
+
+ Input:   address and transfer direction of I2C device
+ 
+ Return:  0 device accessible
+          1 failed to access device
+*************************************************************************/
+unsigned char i2c_rep_start(unsigned char address)
+{
+    return i2c_start( address );
+
+}/* i2c_rep_start */
+
+
+/*************************************************************************
+ Terminates the data transfer and releases the I2C bus
+*************************************************************************/
+void i2c_stop(void)
+{
+    /* send stop condition */
+	TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
+	
+	// wait until stop condition is executed and bus released
+	while(TWCR & (1<<TWSTO));
+
+}/* i2c_stop */
+
+
+/*************************************************************************
+  Send one byte to I2C device
+  
+  Input:    byte to be transfered
+  Return:   0 write successful 
+            1 write failed
+*************************************************************************/
+unsigned char i2c_write( unsigned char data )
+{	
+    uint8_t   twst;
+    
+	// send data to the previously addressed device
+	TWDR = data;
+	TWCR = (1<<TWINT) | (1<<TWEN);
+
+	// wait until transmission completed
+	while(!(TWCR & (1<<TWINT)));
+
+	// check value of TWI Status Register. Mask prescaler bits
+	twst = TW_STATUS & 0xF8;
+	if( twst != TW_MT_DATA_ACK) return 1;
+	return 0;
+
+}/* i2c_write */
+
+
+/*************************************************************************
+ Read one byte from the I2C device, request more data from device 
+ 
+ Return:  byte read from I2C device
+*************************************************************************/
+unsigned char i2c_readAck(void)
+{
+	TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
+	while(!(TWCR & (1<<TWINT)));    
+
+    return TWDR;
+
+}/* i2c_readAck */
+
+
+/*************************************************************************
+ Read one byte from the I2C device, read is followed by a stop condition 
+ 
+ Return:  byte read from I2C device
+*************************************************************************/
+unsigned char i2c_readNak(void)
+{
+	TWCR = (1<<TWINT) | (1<<TWEN);
+	while(!(TWCR & (1<<TWINT)));
+	
+    return TWDR;
+
+}/* i2c_readNak */
-- 
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