static void i2c_init(void)
{
/* i2c control lines */
rcc_periph_clock_enable(RCC_GPIOB);
gpio_mode_setup(GPIOB, GPIO_MODE_AF, GPIO_PUPD_PULLUP, GPIO6 | GPIO7);
gpio_set_output_options(GPIOB, GPIO_OTYPE_OD, GPIO_OSPEED_100MHZ /* GPIO_OSPEED_2MHZ */, GPIO6 | GPIO7);
gpio_set_af(GPIOB, GPIO_AF4, GPIO6 | GPIO7);
rcc_periph_clock_enable(I2C_CLOCK);
i2c_reset(I2C_PORT);
i2c_peripheral_disable(I2C_PORT);
i2c_set_standard_mode(I2C_PORT);
i2c_enable_ack(I2C_PORT);
i2c_set_dutycycle(I2C_PORT, I2C_CCR_DUTY_DIV2); /* default, no need to do this really */
i2c_set_clock_frequency(I2C_PORT, I2C_FREQ);
/* CCR is the number of APB bus cycles in *half* an I2C bus
* cycle. For Sm (100Khz) this ends up as:
* freq * 1MHz / 2 * 100KHz
* freq * 1000000 / 200000
* freq * 5
*
* Similar trise is the number of APB bus cycles in the rise
* time (plus 1). For Sm (1us) this ends up as:
* freq * 1Mhz / (1/1us) + 1
* freq * 1MHz / 1MHz + 1
* freq + 1
*/
/* 42MHz / (100kHz * 2) */
i2c_set_ccr(I2C_PORT, I2C_FREQ * 5);
/* standard mode, freqMhz+1*/
i2c_set_trise(I2C_PORT, I2C_FREQ + 1);
i2c_set_own_7bit_slave_address(I2C_PORT, OWN_ADDRESS);
i2c_peripheral_enable(I2C_PORT);
}
static void setup_i2c_port(enum I2C_FREQ I2C_speed)
{
// Disable I2C if it happens to be enabled
i2c_peripheral_disable(I2C_PORT);
dma_channel_reset(I2C_TX_DMA, I2C_TX_DMA_CHANNEL);
i2c_disable_interrupt(I2C_PORT, (I2C_CR2_ITEVTEN | I2C_CR2_ITERREN));
DISABLE_I2C_INTERRUPT();
reset_i2c_pins();
// set: Source, Destination, and Amount (DMA channel must be disabled)
dma_set_peripheral_address(I2C_TX_DMA, I2C_TX_DMA_CHANNEL, (uint32_t)&I2C_DR(I2C_PORT));
dma_set_memory_address(I2C_TX_DMA, I2C_TX_DMA_CHANNEL, 0);
dma_set_number_of_data(I2C_TX_DMA, I2C_TX_DMA_CHANNEL, 0);
// set the DMA Configuration (DMA_CCRx)
// (BIT 14) mem2mem_mode disabled
dma_set_priority(I2C_TX_DMA, I2C_TX_DMA_CHANNEL, DMA_CCR_PL_HIGH); // (BIT 12:13)
dma_set_memory_size(I2C_TX_DMA, I2C_TX_DMA_CHANNEL, DMA_CCR_MSIZE_8BIT); // (BIT 10:11)
dma_set_peripheral_size(I2C_TX_DMA, I2C_TX_DMA_CHANNEL, DMA_CCR_PSIZE_8BIT); // (BIT 8:9)
dma_enable_memory_increment_mode(I2C_TX_DMA, I2C_TX_DMA_CHANNEL); // (BIT 7)
dma_disable_peripheral_increment_mode(I2C_TX_DMA, I2C_TX_DMA_CHANNEL); // (BIT 6)
// (BIT 5) Circular mode is disabled
dma_set_read_from_memory(I2C_TX_DMA, I2C_TX_DMA_CHANNEL); // (BIT 4)
dma_enable_transfer_error_interrupt(I2C_TX_DMA, I2C_TX_DMA_CHANNEL); // (BIT 3)
dma_disable_half_transfer_interrupt(I2C_TX_DMA, I2C_TX_DMA_CHANNEL); // (BIT 2)
dma_enable_transfer_complete_interrupt(I2C_TX_DMA, I2C_TX_DMA_CHANNEL); // (BIT 1)
// This is the slave address when not transmitting data
i2c_set_own_7bit_slave_address(I2C_PORT, 0x32);
// do not respond to the specified slave address
i2c_disable_ack(I2C_PORT);
// Use DMA to send I2C data
i2c_enable_dma(I2C_PORT);
// set which interrupts I2C uses
i2c_enable_interrupt(I2C_PORT, (I2C_CR2_ITEVTEN | I2C_CR2_ITERREN));
// APB1 is running at 36MHz = T(PCLK1) = 1/36000000 sec.
i2c_set_clock_frequency(I2C_PORT, I2C_CR2_FREQ_36MHZ);
// Set up the hardware for the particular speed
switch (I2C_speed) {
// Values found on Internet for the I2C standard
// STANDARD : SCL max rise time = 1000ns = 1000/1000000000 sec
// FAST : SCL max rise time = 300ns = 300/1000000000 sec
//
// DATASHEET Function:
// TRISE = (T(MAX_SCL_RISE) / T(PCLK1)) + 1
//
// DATASHEET Functions:
// STANDARD :
// T(high) = CCR * T(PCLK1)
// T(low) = CCR * T(PCLK1)
// FAST (DUTY=I2C_CCR_DUTY_DIV2)
// T(high) = CCR * T(PCLK1)
// T(low) = 2 * CCR * T(PCLK1)
// FAST (DUTY=I2C_CCR_DUTY_16_DIV_9) [To reach 400KHz]
// T(high) = 9 * CCR * T(PCLK1)
// T(low) = 16 * CCR * T(PCLK1)
//
// I2C PERIOD:
// STANDARD
// PERIOD = T(high) + T(low) = (2 * CCR * T(PCLK1))
// FAST (DUTY=I2C_CCR_DUTY_DIV2)
// PERIOD = T(high) + T(low) = (3 * CCR * T(PCLK1))
// FAST (DUTY=I2C_CCR_DUTY_16_DIV_9)
// PERIOD = T(high) + T(low) = (25 * CCR * T(PCLK1))
case I2C_400KHz:
// I2C PERIOD: 400KHz = 400000Hz = 1/400000 sec.
i2c_set_fast_mode(I2C_PORT);
// I2C_CCR_DUTY_DIV2 or I2C_CCR_DUTY_16_DIV_9
i2c_set_dutycycle(I2C_PORT, I2C_CCR_DUTY_16_DIV_9);
// CCR = PERIOD / (25 * T(PCLK1))
// CCR = (1/400000) / (25/36000000) = 18/5 = 3.6
// CCR = 4 => I2C PERIOD = 360kHz
// CCR = 3 => I2C PERIOD = 480kHz
i2c_set_ccr(I2C_PORT, 4); // Only fast mode can have a value less than 0x04
// TRISE = ( (300/1000000000) / (1/36000000) ) + 1 = 59/5 = 11.8
// TRISE = 12 => SCL max rise time ~= 305.555ns
// TRISE = 11 => SCL max rise time ~= 277.777ns
i2c_set_trise(I2C_PORT, 11);
break;
case I2C_100KHz:
// I2C PERIOD: 100KHz = 100000Hz = 1/100000 sec.
i2c_set_standard_mode(I2C_PORT);
// I2C_CCR_DUTY_DIV2 or I2C_CCR_DUTY_16_DIV_9
i2c_set_dutycycle(I2C_PORT, I2C_CCR_DUTY_DIV2);
// CCR = PERIOD / (2 * T(PCLK1))
// CCR = (1/100000) / (2/36000000) = 180
i2c_set_ccr(I2C_PORT, 180);
// TRISE = ( (1000/1000000000) / (1/36000000) ) + 1 = 37
i2c_set_trise(I2C_PORT, 37);
break;
case I2C_53KHz:
// ~= 52.91kHz is the slowest I could get to work
// CCR value of 341 works but not 342 or higher
case I2C_50KHz:
default:
// I2C PERIOD: 50KHz = 50000Hz = 1/50000 sec.
i2c_set_standard_mode(I2C_PORT);
// I2C_CCR_DUTY_DIV2 or I2C_CCR_DUTY_16_DIV_9
i2c_set_dutycycle(I2C_PORT, I2C_CCR_DUTY_DIV2);
// CCR = PERIOD / (2 * T(PCLK1))
// CCR = (1/50000) / (2/36000000) = 360
// (341 works but not 342 or higher)
i2c_set_ccr(I2C_PORT, 341);
// TRISE = ( (1000/1000000000) / (1/36000000) ) + 1 = 37
i2c_set_trise(I2C_PORT, 37);
break;
}
i2c_peripheral_enable(I2C_PORT);
// set the priorities for the interrupts
nvic_set_priority(I2C_EV_IRQ, IRQ_PRI_I2C);
nvic_set_priority(I2C_ER_IRQ, IRQ_PRI_ER_I2C);
nvic_set_priority(I2C_DMA_IRQ, IRQ_PRI_DMA_I2C);
}
