Driver for PCF8574 (8-bit I2C GPIO expander)

extras/pcf8574/pcf8574.c

@@ -0,0 +1,68 @@
+/*
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "pcf8574.h"
+#include <i2c/i2c.h>
+
+uint8_t pcf8574_port_read(uint8_t addr)
+{
+	i2c_start();
+	uint8_t res = i2c_write((addr << 1) | 1) ? i2c_read(1) : 0;
+	i2c_stop();
+	return res;
+}
+
+size_t pcf8574_port_read_buf(uint8_t addr, void *buf, size_t len)
+{
+	if (!len || !buf) return 0;
+	uint8_t *_buf = (uint8_t *)buf;
+
+	i2c_start();
+	if (!i2c_write((addr << 1) | 1)) return 0;
+	for (size_t i = 0; i < len; i++)
+		*_buf++ = i2c_read(i == len - 1);
+	i2c_stop();
+	return len;
+}
+
+size_t pcf8574_port_write_buf(uint8_t addr, void *buf, size_t len)
+{
+	if (!len || !buf) return 0;
+	uint8_t *_buf = (uint8_t *)buf;
+
+	i2c_start();
+	if (!i2c_write(addr << 1)) return 0;
+	for (size_t i = 0; i < len; i++)
+		i2c_write(*_buf++);
+	return len;
+}
+
+void pcf8574_port_write(uint8_t addr, uint8_t value)
+{
+	i2c_start();
+	if (i2c_write(addr << 1)) i2c_write(value);
+	i2c_stop();
+}
+
+bool pcf8574_gpio_read(uint8_t addr, uint8_t num)
+{
+	return (bool)((pcf8574_port_read(addr) >> num) & 1);
+}
+
+void pcf8574_gpio_write(uint8_t addr, uint8_t num, bool value)
+{
+	uint8_t bit = (uint8_t)value << num;
+	uint8_t mask = ~(1 << num);
+	pcf8574_port_write (addr, (pcf8574_port_read(addr) & mask) | bit);
+}