From 6d4ad089c5b758ad8af4f68bf385a26ec4e9653a Mon Sep 17 00:00:00 2001
From: Thomas Albers Raviola <thomas@thomaslabs.org>
Date: Thu, 21 Nov 2024 15:55:03 +0100
Subject: Initial commit

---
 src/i2c.c | 103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 src/i2c.c

(limited to 'src/i2c.c')

diff --git a/src/i2c.c b/src/i2c.c
new file mode 100644
index 0000000..cca68c6
--- /dev/null
+++ b/src/i2c.c
@@ -0,0 +1,103 @@
+#include <i2c.h>
+#include <hardware.h>
+
+#define SDA (1 << 0)
+#define SCL (1 << 1)
+
+void
+_delay_ms(uint8_t ms);
+
+void
+i2c_start_condition(void)
+{
+	port_a_data &= ~SDA;
+	_delay_ms(1);
+	port_a_data &= ~SCL;
+	_delay_ms(1);
+}
+
+void
+i2c_restart_condition(void)
+{
+	port_a_data |= SDA;
+	_delay_ms(1);
+	port_a_data |= SCL;
+	_delay_ms(1);
+	i2c_start_condition();
+}
+
+void
+i2c_stop_condition(void)
+{
+	port_a_data |= SCL;
+	_delay_ms(1);
+	port_a_data |= SDA;
+	_delay_ms(1);
+}
+
+void
+i2c_send(uint8_t b)
+{
+	uint8_t i;
+
+	for (i = 0; i < 8; ++i) {
+		if (b & 1)
+			port_a_data |= SDA;
+		else
+			port_a_data &= ~SDA;
+
+		port_a_data |= SCL;
+		_delay_ms(1);
+		port_a_data &= ~SCL;
+		_delay_ms(1);
+
+		b >>= 1;
+	}
+
+	port_a_ctrl = PIO_MODE_3;
+	port_a_ctrl = 0x7D;
+
+	// Read ack
+	port_a_data |= SCL;
+	_delay_ms(1);
+	port_a_data &= ~SCL;
+	_delay_ms(1);
+
+	port_a_ctrl = PIO_MODE_3;
+	port_a_ctrl = 0x7C;
+}
+
+uint8_t
+i2c_recv(uint8_t ack)
+{
+	uint8_t i;
+	uint8_t b = 0;
+
+	port_a_ctrl = PIO_MODE_3;
+	port_a_ctrl = 0x7D;
+
+	for (i = 0; i < 8; ++i) {
+		port_a_data |= SCL;
+		_delay_ms(1);
+		if (port_a_data & 1)
+			b |= 1;
+
+		port_a_data &= ~SCL;
+		_delay_ms(1);
+		b <<= 1;
+	}
+
+	port_a_ctrl = PIO_MODE_3;
+	port_a_ctrl = 0x7C;
+
+	if (ack)
+		port_a_data |= SDA;
+	else
+		port_a_data &= ~SDA;
+
+	port_a_data |= SCL;
+	_delay_ms(1);
+	port_a_data &= ~SCL;
+	_delay_ms(1);
+	return b;
+}
-- 
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