====== T06 - I2C communication ======

===== Task =====

Measure temperature and display its value on Edushield. 

Temperature:

  * T = 1/(log(R_NTC/R)/3975 + 1/298.15)-273.15, where R = 6.8kΩ
  * R_NTC = R*5000/(ADC * 3300) - R

{{:courses:be2m37mam:tasks:therm.png?300|}}

===== Supportive materials =====

Lecture: {{ :courses:be2m37mam:tasks:mam-busses.pdf |busses}}

Project using {{ :courses:be2m37mam:tasks:i2c_f401_hal_lib.zip |HAL library}}

Edushield schematic: {{ :courses:be2m37mam:tasks:edushield_schematic.pdf |}}

Edushield github: [[https://github.com/arduino-edushield/edushield|link]]

Logic analyzer: [[https://learn.sparkfun.com/tutorials/using-the-usb-logic-analyzer-with-sigrok-pulseview/all|link]], [[https://www.youtube.com/watch?v=z8Tdz7eQ8n4|YT]]

<code c>
#define	setbit(reg, bit)      ((reg) |= (1U << (bit)))
#define clearbit(reg, bit)    ((reg) &= (~(1U << (bit))))
#define togglebit(reg, bit)   ((reg) ^= (1U << (bit)))
#define getbit(reg, bit)      (((reg) & (1U << (bit))) >> (bit))

#define DISPLAY_ADDRESS 0x27<<1

void delay(int ms)
{
	volatile int x;
	for (x = 0; x < ms * 50; x++);
}

#define I2C_DELAY	delay(1);
#define I2C_SET_SCL	setbit(GPIOB->ODR, 8);
#define I2C_CLR_SCL     clearbit(GPIOB->ODR, 8);
#define I2C_SET_SDA	setbit(GPIOB->ODR, 9);
#define I2C_CLR_SDA	 clearbit(GPIOB->ODR, 9);

void I2C_ReadBit(void);

// I2C_SDA -> PB9
// I2C_SCL -> PB8

void GPIO_init ()
{
	setbit(RCC->AHB1ENR, 1);
	setbit(GPIOB->MODER, 16);	// SCL
	setbit(GPIOB->OTYPER, 8);
	setbit(GPIOA->OSPEEDR, 16);
	setbit(GPIOA->OSPEEDR, 17);
	setbit(GPIOB->MODER, 18);	// SDA
	setbit(GPIOB->OTYPER, 9);
	setbit(GPIOA->OSPEEDR, 18);
	setbit(GPIOA->OSPEEDR, 19);
}

void I2C_ReadBit(void)
{
    I2C_SET_SDA
    I2C_DELAY

    // set SDA pin as digital input

    I2C_SET_SCL
    I2C_DELAY
    I2C_CLR_SCL

    // set SDA pin as digital output

    I2C_DELAY
}

void I2C_WriteBit(unsigned char c)
{
    if(c > 0) I2C_SET_SDA
    else I2C_CLR_SDA

    I2C_DELAY
    I2C_SET_SCL
    I2C_DELAY
    I2C_CLR_SCL
}

void I2C_Init()
{
    I2C_SET_SDA
    I2C_SET_SCL
    I2C_DELAY
}

void I2C_Start()
{
    I2C_SET_SCL
    I2C_DELAY
    I2C_SET_SDA
    I2C_DELAY
    I2C_CLR_SDA
    I2C_DELAY
    I2C_CLR_SCL
    I2C_DELAY
}

void I2C_Stop()
{
    I2C_DELAY
    I2C_CLR_SDA
    I2C_DELAY
    I2C_SET_SCL
    I2C_DELAY
    I2C_SET_SDA
}

unsigned char I2C_Write(unsigned char c)
{
    for (char i = 0; i < 8; i++)
    {
        I2C_WriteBit(c & 128);

        c <<= 1;
    }
    I2C_SET_SDA

    return 0;
}

void I2C_Send(unsigned char addr, unsigned char reg, unsigned char data)
{
    I2C_Start();
    I2C_Write(addr);
    I2C_ReadBit(); // ACK
    I2C_Write(reg);
    I2C_ReadBit(); // ACK
    I2C_Write(data);
    I2C_ReadBit(); // ACK
    I2C_Stop();
}

int main()
{
	GPIO_init();
	I2C_Init();

	const unsigned char digits[10] = {0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F};

	// your code
	I2C_Send (DISPLAY_ADDRESS, 0, digits[7]);
	I2C_Send (DISPLAY_ADDRESS, 1, digits[5]);
	I2C_Send (DISPLAY_ADDRESS, 2, digits[3]);
	I2C_Send (DISPLAY_ADDRESS, 3, digits[1]);

    while(1)
    {

    }
}

</code>