Enhance I2C initialization with detailed configuration constants and improve internal state checks for better error handling

Author: taisirhassan

include/i2c.h

@@ -4,11 +4,22 @@
 #include "common.h"
 #include <stdint.h>
 
-/* Initialize I2C Controller
-   I2C Frequency = (100 kHz) / (2 ^ clkdiv)
-   Max frequency clkdiv = b000, 100kHz
-   Min frequency clkdiv = b111, 781.25 Hz
-*/
+/*
+ * Configuration Constants
+ * These define the behavior and timing characteristics of the I2C interface
+ */
+#define I2C_POLL_TIMEOUT 2000 // Maximum cycles to wait during I2C operations
+#define I2C_STRETCH_DELAY 100 // Microseconds to delay during clock stretching
+#define I2C_CLOCK_FREQ 100000 // Default I2C clock frequency (100 kHz)
+
+/*
+ * Initialize I2C controller with specified clock settings
+ * clkdiv: Clock divider (0-7) determines I2C frequency:
+ *   0 = 100kHz (standard mode)
+ *   1 = 50kHz
+ *   2 = 25kHz
+ *   etc.
+ */
 w_status_t i2c_init(uint8_t clkdiv);
 
 w_status_t i2c_write_data(uint8_t address, const uint8_t *data, uint8_t len);

pic18f26k83/i2c.c

@@ -2,9 +2,58 @@
 
 #include "i2c.h"
 
-#ifndef I2C_POLL_TIMEOUT
-#define I2C_POLL_TIMEOUT 2000
-#endif
+/* Private function declarations */
+static void clear_i2c_buffers(void);
+static w_status_t check_i2c_state(void);
+static w_status_t wait_for_idle(void);
+static w_status_t i2c_write(uint8_t address, const uint8_t *data, uint8_t len);
+static w_status_t i2c_read(uint8_t address, uint8_t *data, uint8_t len);
+
+/*
+ * Clear I2C buffers and ensure they're in a known state
+ */
+static void clear_i2c_buffers(void) {
+    // Clear the buffer flag and flush any pending data
+    I2C1STAT1bits.CLRBF = 1;
+    while (I2C1STAT1bits.RXBF) {
+        (void)I2C1RXB; // Read and discard any data
+    }
+}
+
+/*
+ * Check the current state of the I2C module
+ * Verifies module is enabled and no errors are present
+ */
+static w_status_t check_i2c_state(void) {
+    if (!I2C1CON0bits.EN) {
+        return W_IO_ERROR; // Module not enabled
+    }
+
+    // Check for any error conditions
+    if (I2C1ERRbits.BCLIF || // Bus collision
+        I2C1ERRbits.BTOIF || // Bus timeout
+        I2C1ERRbits.NACKIF) { // Not acknowledged
+
+        I2C1ERR = 0; // Clear error flags
+        return W_IO_ERROR;
+    }
+
+    return W_SUCCESS;
+}
+
+/*
+ * Wait for the I2C bus to become idle
+ * Monitors the Bus Free bit with timeout protection
+ */
+static w_status_t wait_for_idle(void) {
+    unsigned int timeout = 0;
+    while (!I2C1STAT0bits.BFRE) {
+        if (timeout++ >= I2C_POLL_TIMEOUT) {
+            return W_IO_TIMEOUT;
+        }
+    }
+    return W_SUCCESS;
+}
 
 w_status_t i2c_init(uint8_t clkdiv) {
     // CSTR Enable clocking; S Cleared by hardware after Start; MODE 7-bit address; EN enabled; RSEN