/* * This example is not extensively tested and only * meant as a simple explanation and for inspiration. * NO WARRANTY of ANY KIND is provided. */ #include #include #include #include "nrf_delay.h" #include "app_uart.h" #include "bsp.h" #include "app_error.h" #include "app_mpu9255.h" #include "nrf_log.h" #include "nrf_log_ctrl.h" #include "nrf_log_default_backends.h" /**@brief Function for initializing the nrf log module. */ static void log_init(void) { ret_code_t err_code = NRF_LOG_INIT(NULL); APP_ERROR_CHECK(err_code); NRF_LOG_DEFAULT_BACKENDS_INIT(); } /* Pins to connect MPU. Pinout is different for nRF51 DK and nRF52 DK * and therefore I have added a conditional statement defining different pins * for each board. This is only for my own convenience. */ #define MPU_TWI_SCL_PIN NRF_GPIO_PIN_MAP(0, 28) #define MPU_TWI_SDA_PIN NRF_GPIO_PIN_MAP(0, 29) #define MPU_INT_PIN NRF_GPIO_PIN_MAP(0, 30) #define MPU_ADDRESS 0x68 /* The buffer length, TWIM_RX_BUF_LENGTH, defines how many samples will fit in the buffer. Each sample * may contain accelerometer data and/or gyroscope data and/or temperature. What data to read is defined by * TWIM_RX_BUF_WIDTH and reigster address in p_tx_data.*/ #define TWIM_RX_BUF_LENGTH 10 /* The buffer width, TWIM_RX_BUF_WIDTH, and tx buffer, p_tx_data, defines how much and what kind of data to read out for every sample. For example: * A buffer width of 6 and register read address MPU_REG_ACCEL_XOUT_H will read out accelerometer data only. * A buffer width of 14 and register read address MPU_REG_ACCEL_XOUT_H will read out all acceleromter, temperateure, and gyroscope data. * A buffer width of 6 and register start address MPU_REG_GYRO_XOUT_H will read out gyroscope data only. */ #define TWIM_RX_BUF_WIDTH 6 // Reading accelerometer only /* Define a type with a two dimensioanal array, TWIM_RX_BUF_WIDTH wide and TWIM_RX_BUF_LENGTH long, holding a list of MPU sensor data */ typedef struct ArrayList { uint8_t buffer[TWIM_RX_BUF_WIDTH]; }array_list_t; /* Declare an RX buffer to hold the sensor data in the MPU we want to read. * TWIM_RX_BUF_LENGTH defines how many samples of accelerometer data and/or gyroscope data and/or temperature * data we want to read out. What kind of sensor values we read out is defined by the register address * held in p_tx_data and the buffer width TWIM_RX_BUF_WIDTH. */ array_list_t p_rx_buffer[TWIM_RX_BUF_LENGTH]; /* Declare a simple TX buffer holding the first register in MPU we want to read from. */ //uint8_t p_tx_buffer[1] = {MPU_REG_ACCEL_XOUT_H}; // Reading accelerometer only //uint8_t p_tx_buffer[1] = {MPU_REG_GYRO_XOUT_H}; // Reading gyros uint8_t p_tx_buffer[1] = {MPU_AK89XX_REG_HXL}; // Reading mango /* Flag to indicate to the applications main context that TWIM_RX_BUF_LENGTH number of samples have been transferred from MPU */ volatile bool twi_transfers_complete = false; /** * @brief Initialize the TWI Master module with PPI triggered * R/W operations started by a counter module */ static void twi_with_easy_dma_setup() { // Disable the TWIM module while we reconfigure it NRF_TWIM0->ENABLE = TWIM_ENABLE_ENABLE_Disabled << TWIM_ENABLE_ENABLE_Pos; NRF_TWIM0->SHORTS = 0; NVIC_DisableIRQ(SPI0_TWI0_IRQn); NVIC_ClearPendingIRQ(SPI0_TWI0_IRQn); // Configure a gpiote channel to generate an event on a polarity change from // low to high generated the MPU interrupt pin. uint8_t gpiote_ch_mpu_int_event = 0; NRF_GPIOTE->CONFIG[gpiote_ch_mpu_int_event] = ( (GPIOTE_CONFIG_MODE_Event << GPIOTE_CONFIG_MODE_Pos) | (MPU_INT_PIN << GPIOTE_CONFIG_PSEL_Pos) | (GPIOTE_CONFIG_POLARITY_LoToHi << GPIOTE_CONFIG_POLARITY_Pos)); NRF_TWIM0->PSEL.SCL = MPU_TWI_SCL_PIN; NRF_TWIM0->PSEL.SDA = MPU_TWI_SDA_PIN; NRF_TWIM0->FREQUENCY = TWI_FREQUENCY_FREQUENCY_K400; // Load TWI TX buffer into TWI module. Set number of bytes to write pr transfer, max count, to one. // Disable the EasyDMA list functionality for TWI TX. NRF_TWIM0->TXD.PTR = (uint32_t)&p_tx_buffer; NRF_TWIM0->TXD.MAXCNT = 1; NRF_TWIM0->TXD.LIST = TWIM_TXD_LIST_LIST_Disabled << TWIM_TXD_LIST_LIST_Pos; // Point to TWI RX buffer. Set number of bytes to read pr transfer, max count, to TWIM_RX_BUF_WIDTH. // Disable the EasyDMA list functionality for TWI TX NRF_TWIM0->RXD.PTR = (uint32_t)&p_rx_buffer; NRF_TWIM0->RXD.MAXCNT = TWIM_RX_BUF_WIDTH; NRF_TWIM0->RXD.LIST = TWIM_RXD_LIST_LIST_ArrayList << TWIM_RXD_LIST_LIST_Pos; // Make sure that MPU address is set NRF_TWIM0->ADDRESS = MPU_ADDRESS; // Enable shortcuts that starts a read right after a write and sends a stop condition after last TWI read NRF_TWIM0->SHORTS = (TWIM_SHORTS_LASTTX_STARTRX_Enabled << TWIM_SHORTS_LASTTX_STARTRX_Pos) | (TWIM_SHORTS_LASTRX_STOP_Enabled << TWIM_SHORTS_LASTRX_STOP_Pos); // Configure PPI channel // Use MPU interrupt pin as event // Start timer 0 on event to count number of transfers // Also start TWI transfers on event // Enable PPI channel NRF_PPI->CH[0].EEP = (uint32_t)&NRF_GPIOTE->EVENTS_IN[gpiote_ch_mpu_int_event]; NRF_PPI->CH[0].TEP = (uint32_t)&NRF_TIMER0->TASKS_COUNT; NRF_PPI->FORK[0].TEP = (uint32_t)&NRF_TWIM0->TASKS_STARTTX; // Enable the TWIM module NRF_TWIM0->ENABLE = TWIM_ENABLE_ENABLE_Enabled << TWIM_ENABLE_ENABLE_Pos; } /** * @brief Initialize the counter in Timer 0 used to count number of * TWI transfers from MPU */ void twi_transfer_counter_init() { // Disable and clear any pending Timer 0 interrupts NVIC_DisableIRQ(TIMER0_IRQn); NVIC_ClearPendingIRQ(TIMER0_IRQn); // Stop timer if running NRF_TIMER0->TASKS_STOP = 1; // Enabel shortcut to clear the compare register on a compare event NRF_TIMER0->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Enabled << TIMER_SHORTS_COMPARE0_CLEAR_Pos; // Use timer 0 as counter NRF_TIMER0->MODE = TIMER_MODE_MODE_Counter << TIMER_MODE_MODE_Pos; // Set bit mode to 8 bit. NRF_TIMER0->BITMODE = TIMER_BITMODE_BITMODE_08Bit << TIMER_BITMODE_BITMODE_Pos; // Set compare register to length of RX buffer. This will trigger an event each time // the RX buffer is full NRF_TIMER0->CC[0] = TWIM_RX_BUF_LENGTH; // Enable interrupts on counter compare NRF_TIMER0->INTENSET = TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos; } /** * @brief Start the transfers */ void start_transfers(void) { // Enable timer interrupt NVIC_EnableIRQ(TIMER0_IRQn); // Start counter NRF_TIMER0->TASKS_START = 1; // Enable the PPI channel tying MPU interrupt pin to TWIM module NRF_PPI->CHEN = PPI_CHEN_CH0_Enabled << PPI_CHEN_CH0_Pos; } /** * @brief Timer event handler triggered on counter compare, i.e. everytime * TWI RX buffer is full */ void TIMER0_IRQHandler(void) { // Clear timer event NRF_TIMER0->EVENTS_COMPARE[0] = 0; // Reset the TWIM RX pointer to initial address of RX buffer NRF_TWIM0->RXD.PTR = (uint32_t)&p_rx_buffer; // Toggle a LED for show nrf_gpio_pin_toggle(LED_1); // Set flag to notify main context of the new data available twi_transfers_complete = true; } /** * @brief MPU initialization. * Just the usual way. Nothing special here */ void mpu_init() { uint32_t err_code; // MPU setup err_code = app_mpu_init(); APP_ERROR_CHECK(err_code); // Check for errors in return value app_mpu_config_t p_mpu_config = MPU_DEFAULT_CONFIG(); p_mpu_config.smplrt_div = 19; p_mpu_config.accel_config.afs_sel = AFS_2G; p_mpu_config.gyro_config.fs_sel = GFS_250DPS; err_code = app_mpu_config(&p_mpu_config); APP_ERROR_CHECK(err_code); // Check for errors in return value // Enable magnetometer app_mpu_magn_config_t magnetometer_config; magnetometer_config.mode = CONTINUOUS_MEASUREMENT_100Hz_MODE; err_code = app_mpu_magnetometer_init(&magnetometer_config); APP_ERROR_CHECK(err_code); // Check for errors in return value app_mpu_int_pin_cfg_t p_int_pin_cfg = MPU_DEFAULT_INT_PIN_CONFIG(); p_int_pin_cfg.int_rd_clear = 1; // Read operation will clear the MPU interrupt err_code = app_mpu_int_cfg_pin(&p_int_pin_cfg); APP_ERROR_CHECK(err_code); // Check for errors in return value app_mpu_int_enable_t p_int_enable = MPU_DEFAULT_INT_ENABLE_CONFIG(); p_int_enable.data_rdy_en = 1; // Enable interrupt on completed sample err_code = app_mpu_int_enable(&p_int_enable); APP_ERROR_CHECK(err_code); // Check for errors in return value } /** * @brief Function for application main entry. */ int main(void) { LEDS_CONFIGURE(LEDS_MASK); LEDS_OFF(LEDS_MASK); // Initialize. log_init(); NRF_LOG_INFO("\033[2J\033[;H"); // Clear screen mpu_init(); // Start execution. NRF_LOG_INFO("MPU EasyDMA using GPIOTE and registers example."); // Initiate counter to count number of TWI transfers twi_transfer_counter_init(); // Reconfigure TWI to use PPI and easyDMA twi_with_easy_dma_setup(); // Starting the transfers start_transfers(); uint32_t sample_nr = 0; // Variable holding number of samples read from MPU accel_values_t acc_values; // Variable to temporarily hold MPU accelerometer data gyro_values_t gyro_values; magn_values_t magn_values; while (true) { if(NRF_LOG_PROCESS() == false) { nrf_gpio_pin_set(LED_4); // Turn LED OFF when CPU is sleeping // Wait for new available data while(twi_transfers_complete == false) { // Make sure any pending events are cleared __SEV(); __WFE(); // Enter System ON sleep mode __WFE(); } nrf_gpio_pin_clear(LED_4); // Turn LED ON when CPU is working // Print header with total number of samples received NRF_LOG_RAW_INFO("\033[3;1HSample %d:\r\n", TWIM_RX_BUF_LENGTH * sample_nr++); // THIS FOR LOOP ASSUMES THAT TWIM_RX_BUF_WIDTH IS 6 BYTES AND THAT ONLY ACCELEROMETER DATA IS SAMPLED // IF A WIDER BUFFER IS USED TO SAMPLE TEMPERATURE AND GYROSCOPE AS WELL YOU SHOULD CHANGE THIS LOOP // TO PRINT EVERYTHING uint8_t *data; // Itterate through entire RX buffer for(uint8_t j = 0; j