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); }