From 7b8c37d235c77d881db4184a798fc4b72a1fa279 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Mon, 15 Jan 2018 10:16:13 +0100
Subject: Add Software I2C implementation

---
 Makefile                  |   5 ++
 include/driver/soft_i2c.h |  26 ++++++++++
 src/driver/soft_i2c.cc    | 121 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 152 insertions(+)
 create mode 100644 include/driver/soft_i2c.h
 create mode 100644 src/driver/soft_i2c.cc

diff --git a/Makefile b/Makefile
index a6f03c9..b7089b4 100644
--- a/Makefile
+++ b/Makefile
@@ -27,6 +27,11 @@ ifneq ($(findstring sharp96,${drivers}), )
 	COMMON_FLAGS += -DSHARP96_CS_PIN=GPIO::${sharp96_cs_pin}
 endif
 
+ifneq ($(findstring softi2c,${drivers}), )
+	TARGETS += src/driver/soft_i2c.cc
+	COMMON_FLAGS += -DDRIVER_SOFTI2C
+endif
+
 ifeq (${timer_cycles}, 1)
 	COMMON_FLAGS += -DTIMER_CYCLES
 endif
diff --git a/include/driver/soft_i2c.h b/include/driver/soft_i2c.h
new file mode 100644
index 0000000..aff63e3
--- /dev/null
+++ b/include/driver/soft_i2c.h
@@ -0,0 +1,26 @@
+#ifndef SOFTI2C_H
+#define SOFTI2C_H
+
+class SoftI2C {
+	private:
+		SoftI2C(const SoftI2C &copy);
+
+		unsigned char sda, scl;
+
+		void start();
+		void stop();
+		bool tx(unsigned char byte);
+		unsigned char rx(bool send_ack);
+
+	public:
+		SoftI2C(unsigned char sda, unsigned char scl) : sda(sda), scl(scl) {}
+		signed char setup();
+		void scan(unsigned int *results);
+		signed char xmit(unsigned char address,
+				unsigned char tx_len, unsigned char *tx_buf,
+				unsigned char rx_len, unsigned char *rx_buf);
+};
+
+extern SoftI2C i2c;
+
+#endif
diff --git a/src/driver/soft_i2c.cc b/src/driver/soft_i2c.cc
new file mode 100644
index 0000000..f8ee052
--- /dev/null
+++ b/src/driver/soft_i2c.cc
@@ -0,0 +1,121 @@
+#include "driver/soft_i2c.h"
+#include "driver/gpio.h"
+
+signed char SoftI2C::setup()
+{
+	gpio.write(sda, 0);
+	gpio.write(scl, 0);
+	return 0;
+}
+
+void SoftI2C::start()
+{
+	gpio.input(sda);
+	gpio.input(scl);
+	//
+	gpio.output(sda);
+	//
+	gpio.output(scl);
+}
+
+void SoftI2C::stop()
+{
+	gpio.output(sda);
+	//
+	gpio.input(scl);
+	//
+	gpio.input(sda);
+}
+
+bool SoftI2C::tx(unsigned char byte)
+{
+	unsigned char got_ack = 0;
+	for (unsigned char i = 0; i <= 8; i++) {
+		if ((byte & 0x80) || (i == 8)) {
+			gpio.input(sda);
+		} else {
+			gpio.output(sda);
+		}
+		byte <<= 1;
+		//
+		gpio.input(scl);
+		//
+		if (i == 8) {
+			if (!gpio.read(sda)) {
+				got_ack = 1;
+			}
+		}
+		gpio.output(scl);
+		//
+	}
+	return got_ack;
+}
+
+unsigned char SoftI2C::rx(bool send_ack)
+{
+	unsigned char byte = 0;
+	gpio.input(sda);
+	for (unsigned char i = 0; i <= 8; i++) {
+		//
+		gpio.input(scl);
+		//
+		if ((i < 8) && gpio.read(sda)) {
+			byte |= 1 << (7 - i);
+		}
+		//
+		gpio.output(scl);
+		//
+		if ((i == 7) && send_ack) {
+			gpio.output(sda);
+		} else if ((i == 8) && send_ack) {
+			gpio.input(sda);
+		}
+	}
+	return byte;
+}
+
+void SoftI2C::scan(unsigned int *results)
+{
+	unsigned char i2caddr;
+	for (unsigned char address = 0; address < 128; address++) {
+
+		i2caddr = (address << 1) | 1;
+
+		start();
+
+		if (tx(i2caddr)) {
+			results[address / (8 * sizeof(unsigned int))] |= 1 << (address % (8 * sizeof(unsigned int)));
+		}
+	}
+	stop();
+}
+
+signed char SoftI2C::xmit(unsigned char address,
+		unsigned char tx_len, unsigned char *tx_buf,
+		unsigned char rx_len, unsigned char *rx_buf)
+{
+	unsigned char i;
+
+	if (tx_len) {
+		start();
+		tx((address << 1) | 0);
+
+		for (i = 0; i < tx_len; i++) {
+			tx(tx_buf[i]);
+		}
+	}
+	if (rx_len) {
+		start();
+		tx((address << 1) | 1);
+
+		for (i = 1; i <= rx_len; i++) {
+			rx_buf[i] = rx((i < rx_len) * 1);
+		}
+	}
+
+	stop();
+
+	return 0;
+}
+
+SoftI2C i2c(GPIO::p1_6, GPIO::p1_7);
-- 
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