I2C code formatting, README fix (#462)

extras/i2c/README.md

@@ -2,11 +2,12 @@
 
 This time a driver for the excellent esp-open-rtos. This is a bit banging I2C driver based on the Wikipedia pesudo C code [1].
 
-### Usage
+### Basic usage
 
-````
+```C
 #include <i2c.h>
 
+#define BUS     (0)
 #define SCL_PIN (0)
 #define SDA_PIN (2)
 
@@ -14,19 +15,19 @@ uint8_t slave_addr = 0x20;
 uint8_t reg_addr = 0x1f;
 uint8_t reg_data;
 
-i2c_init(SCL_PIN, SDA_PIN);
+i2c_init(BUS, SCL_PIN, SDA_PIN, I2C_FREQ_400K);
 
 // Write 1 byte to slave register
-int err = i2c_slave_write(slave_addr, &reg_addr, &data, 1);
+int err = i2c_slave_write(BUS, slave_addr, &reg_addr, &data, 1);
 if (err != 0)
 {
 	// do something with error
 }
 
 // Issue write to slave, sending reg_addr, followed by reading 1 byte
-err = i2c_slave_read(slave_addr, &reg_addr, &reg_data, 1);
+err = i2c_slave_read(BUS, slave_addr, &reg_addr, &reg_data, 1);
 
-````
+```
 
 For details please see `extras/i2c/i2c.h`.
 

extras/i2c/i2c.c

@@ -22,10 +22,13 @@
  * THE SOFTWARE.
  */
 
+#include "i2c.h"
+
 #include <esp8266.h>
 #include <espressif/esp_misc.h> // sdk_os_delay_us
 #include <espressif/esp_system.h>
-#include "i2c.h"
+#include <FreeRTOS.h>
+#include <task.h>
 
 //#define I2C_DEBUG true
 
@@ -37,7 +40,28 @@
 
 #define CLK_STRETCH  (10)
 
+// Following array contain delay values for different frequencies
+// Warning: 1 is minimal, that mean at 80MHz clock, frequency max is 320kHz
+const static uint8_t i2c_freq_array[][2] = {
+    [I2C_FREQ_80K]  = {255, 35},
+    [I2C_FREQ_100K] = {100, 20},
+    [I2C_FREQ_400K] = {10, 1},
+    [I2C_FREQ_500K] = {6, 1}
+};
+
 static uint8_t freq; // Store CPU frequency for optimisation speed in delay function (Warning: Don't change CPU frequency during a transaction)
+
+// Bus settings
+typedef struct i2c_bus_description
+{
+  uint8_t g_scl_pin;  // SCL pin
+  uint8_t g_sda_pin;  // SDA pin
+  i2c_freq_t frequency;  // Frequency
+  bool started;
+  bool flag;
+  bool force;
+} i2c_bus_description_t;
+
 static i2c_bus_description_t i2c_bus[MAX_I2C_BUS];
 
 inline bool i2c_status(uint8_t bus)
@@ -136,7 +160,8 @@ void i2c_start(uint8_t bus)
         (void) read_sda(bus);
         i2c_delay(bus);
         uint32_t clk_stretch = CLK_STRETCH;
-        while (read_scl(bus) == 0 && clk_stretch--) ;
+        while (read_scl(bus) == 0 && clk_stretch--)
+            ;
         // Repeated start setup time, minimum 4.7us
         i2c_delay(bus);
     }
@@ -158,7 +183,8 @@ bool i2c_stop(uint8_t bus)
     clear_sda(bus);
     i2c_delay(bus);
     // Clock stretching
-    while (read_scl(bus) == 0 && clk_stretch--) ;
+    while (read_scl(bus) == 0 && clk_stretch--)
+        ;
     // Stop bit setup time, minimum 4us
     i2c_delay(bus);
     // SCL is high, set SDA from 0 to 1
@@ -185,7 +211,8 @@ static void i2c_write_bit(uint8_t bus, bool bit)
     }
     i2c_delay(bus);
     // Clock stretching
-    while (read_scl(bus) == 0 && clk_stretch--) ;
+    while (read_scl(bus) == 0 && clk_stretch--)
+        ;
     // SCL is high, now data is valid
     // If SDA is high, check that nobody else is driving SDA
     if (bit && read_sda(bus) == 0) {
@@ -204,7 +231,8 @@ static bool i2c_read_bit(uint8_t bus)
     (void) read_sda(bus);
     i2c_delay(bus);
     // Clock stretching
-    while (read_scl(bus) == 0 && clk_stretch--) ;
+    while (read_scl(bus) == 0 && clk_stretch--)
+        ;
     // SCL is high, now data is valid
     bit = read_sda(bus);
     i2c_delay(bus);

extras/i2c/i2c.h

@@ -21,6 +21,10 @@
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
+/**
+ * I2C driver for ESP8266 written for use with esp-open-rtos
+ * Based on https://en.wikipedia.org/wiki/I²C#Example_of_bit-banging_the_I.C2.B2C_Master_protocol
+ */
 
 #ifndef __I2C_H__
 #define __I2C_H__
@@ -28,62 +32,36 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <errno.h>
-#include <FreeRTOS.h>
-#include <task.h>
 
 #ifdef	__cplusplus
 extern "C" {
 #endif
 
-
+/**
-/*
  * Define i2c bus max number
  */
+#ifndef MAX_I2C_BUS
     #define MAX_I2C_BUS 2
+#endif
 
-
+typedef enum
-/*
+{
- *  following array contain value for different frequency
+ 	I2C_FREQ_80K = 0,//!< I2C_FREQ_80K
- *  Warning : 1 is minimal, that mean at 80MHz clock, frequency max is 320kHz
+ 	I2C_FREQ_100K,   //!< I2C_FREQ_100K
- *  Array format is  { {160MHz, 80MHz} ,  {160MHz, 80MHz} , ... }
+ 	I2C_FREQ_400K,   //!< I2C_FREQ_400K
- */
+ 	I2C_FREQ_500K,   //!< I2C_FREQ_500K
-#define NB_FREQ_AVAILABLE 4
-
- typedef enum {
- 	I2C_FREQ_80K = 0,
- 	I2C_FREQ_100K,
- 	I2C_FREQ_400K,
- 	I2C_FREQ_500K,
 } i2c_freq_t;
 
-const static uint8_t i2c_freq_array[NB_FREQ_AVAILABLE][2] = { {255,35}, {100,20}, {10,1}, {6,1} } ;
-
 /**
  * Device descriptor
  */
-typedef struct i2c_dev {
+typedef struct i2c_dev
+{
   uint8_t bus;
   uint8_t addr;
 } i2c_dev_t;
 
-/**
+/// Level 0 API
- * Bus settings
- */
-typedef struct i2c_bus_description {
-  uint8_t g_scl_pin;  // Scl pin
-  uint8_t g_sda_pin;  // Sda pin
-  uint8_t frequency;  // frequency selection
-  bool started;
-  bool flag;
-  bool force;
-} i2c_bus_description_t ;
-
-
-// I2C driver for ESP8266 written for use with esp-open-rtos
-// Based on https://en.wikipedia.org/wiki/I²C#Example_of_bit-banging_the_I.C2.B2C_Master_protocol
-// With calling overhead, we end up at ~320kbit/s
-
-//Level 0 API
 
 /**
  * Init bitbanging I2C driver on given pins
@@ -137,7 +115,7 @@ bool i2c_stop(uint8_t bus);
  */
 bool i2c_status(uint8_t bus);
 
-//Level 1 API (Don't need functions above)
+/// Level 1 API (Don't need functions above)
 
 /**
  * This function will allow you to force a transmission I2C, cancel current transmission.