updated math functions

module06/ex00/i2c.c

@@ -0,0 +1,26 @@
+#include "header.h"
+
+#define TWI_PRESCALE_VALUE	1											// can be 1, 4, 16, 64
+#define TWI_FREQ			100000UL									// 100kHz I2C
+#define SLAVE_ADDRESS		42											// 22.3.3 : address 0000000 and 1111xxx are reserved, 42 is 0101010
+
+void i2c_init(void) {
+    TWSR = TWI_PRESCALE_SET(TWI_PRESCALE_VALUE);						// 22.9.3 : (Status Register) set prescaler
+    TWBR = ((F_CPU / TWI_FREQ) - 16) / (2 * TWI_PRESCALE_VALUE);		// 22.9.1 : (Bit Rate Register) set SCL frequency (formula from datasheet, 22.5.2)
+}
+
+void i2c_start(void) {
+    TWCR = SEND_START_CONDITION;										// 22.9.2 : (Control Register) send Start condition (22.7.1) ! writting 1 to TWINT clears it (set it to 0)
+    while (!(TEST(TWCR, TWINT)));										// p225 example code : Wait for TWINT Flag set. This indicates that the START condition has been transmitted
+
+	uint8_t status = TWSR & 0b11111000;									// p225 example code : Check value of TWI Status Register. Mask prescaler bits. If status different from START go to ERROR
+	uart_printstr_itoa_base_endl(status);
+    if (status != TW_START && status != TW_REP_START) {
+        TWCR = SEND_STOP_CONDITION;
+        return;
+    }
+}
+
+void i2c_stop(void) {
+    TWCR = SEND_STOP_CONDITION;											// 22.9.2 : send stop condition
+}