From f6972a43581b24281b322a6f8d2bf02dafbe4433 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Thu, 16 Aug 2018 12:58:24 +0200
Subject: configurable i2c bitrate on arduino nano

---
 src/arch/arduino-nano/Makefile.inc  | 4 ++++
 src/arch/arduino-nano/driver/i2c.cc | 6 +++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

(limited to 'src/arch')

diff --git a/src/arch/arduino-nano/Makefile.inc b/src/arch/arduino-nano/Makefile.inc
index d481fa2..18a6563 100644
--- a/src/arch/arduino-nano/Makefile.inc
+++ b/src/arch/arduino-nano/Makefile.inc
@@ -32,6 +32,10 @@ ifneq ($(findstring stdin,${arch_drivers}), )
 	TARGETS += src/arch/arduino-nano/driver/stdin.cc
 endif
 
+ifneq (${i2c_freq}, )
+	COMMON_FLAGS += -DF_I2C=${i2c_freq}
+endif
+
 OBJECTS = ${TARGETS:.cc=.o}
 
 .cc.o:
diff --git a/src/arch/arduino-nano/driver/i2c.cc b/src/arch/arduino-nano/driver/i2c.cc
index cfbea59..0a2f595 100644
--- a/src/arch/arduino-nano/driver/i2c.cc
+++ b/src/arch/arduino-nano/driver/i2c.cc
@@ -3,6 +3,10 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
 
+#ifndef F_I2C
+#define F_I2C 100000UL
+#endif
+
 inline void await_twint(unsigned char twcr_values)
 {
 	TWCR = twcr_values | _BV(TWINT) | _BV(TWIE);
@@ -99,7 +103,7 @@ static signed char i2c_receive(uint8_t len, uint8_t *data)
 signed char I2C::setup()
 {
 	TWSR = 0;
-	TWBR = ((F_CPU / 100000UL) - 16) / 2;
+	TWBR = ((F_CPU / F_I2C) - 16) / 2;
 
 	return 0;
 }
-- 
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