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//sec 2017
#define n_tx_bytes 2 //only as many as needed for application
#define n_rx_bytes 2 //only as many as needed for application
#define scl_pin 0 //XL1, need to disconnect from clock
#define sda_pin 1 //XL2, need to disconnect from clock
static uint8_t txdata[n_tx_bytes] = {0};
static uint8_t rxdata[n_rx_bytes] = {0};
void twi_set_cnts(uint8_t n_tx, uint8_t n_rx){
NRF_TWIM0->TXD.MAXCNT = (n_tx << TWIM_TXD_MAXCNT_MAXCNT_Pos) & TWIM_TXD_MAXCNT_MAXCNT_Msk;
NRF_TWIM0->RXD.MAXCNT = (n_rx << TWIM_RXD_MAXCNT_MAXCNT_Pos) & TWIM_RXD_MAXCNT_MAXCNT_Msk;
NRF_TWIM0->TXD.PTR = (uint32_t)(&txdata);
NRF_TWIM0->RXD.PTR = (uint32_t)(&rxdata);
}
void twi_setup(){
NRF_TWIM0->ENABLE = (TWI_ENABLE_ENABLE_Disabled << TWI_ENABLE_ENABLE_Pos) & TWI_ENABLE_ENABLE_Msk;
NRF_GPIO->PIN_CNF[scl_pin] = (GPIO_PIN_CNF_DRIVE_S0D1 << GPIO_PIN_CNF_DRIVE_Pos) & GPIO_PIN_CNF_DRIVE_Msk;
NRF_GPIO->PIN_CNF[sda_pin] = (GPIO_PIN_CNF_DRIVE_S0D1 << GPIO_PIN_CNF_DRIVE_Pos) & GPIO_PIN_CNF_DRIVE_Msk;
NRF_GPIO->DIRCLR = (1<<scl_pin)|(1<<sda_pin); //set SDA/SCL as inputs (likely not necessary)
NRF_TWIM0->PSEL.SCL = ((scl_pin << TWIM_PSEL_SCL_PIN_Pos) & TWIM_PSEL_SCL_PIN_Msk)
| ((TWIM_PSEL_SCL_CONNECT_Connected << TWIM_PSEL_SCL_CONNECT_Pos) & TWIM_PSEL_SCL_CONNECT_Msk);
NRF_TWIM0->PSEL.SDA = ((sda_pin << TWIM_PSEL_SDA_PIN_Pos) & TWIM_PSEL_SDA_PIN_Msk)
| ((TWIM_PSEL_SDA_CONNECT_Connected << TWIM_PSEL_SDA_CONNECT_Pos) & TWIM_PSEL_SDA_CONNECT_Msk);
NRF_TWIM0->FREQUENCY = (TWI_FREQUENCY_FREQUENCY_K100 << TWI_FREQUENCY_FREQUENCY_Pos) & TWI_FREQUENCY_FREQUENCY_Msk;
NRF_TWIM0->ADDRESS = (0x58 << TWI_ADDRESS_ADDRESS_Pos) & TWI_ADDRESS_ADDRESS_Msk;
NRF_TWIM0->TXD.PTR = (uint32_t)(&txdata);
NRF_TWIM0->RXD.PTR = (uint32_t)(&rxdata);
twi_set_cnts(n_tx_bytes, n_rx_bytes);
//set up short between LASTTX and STOP and between LASTRX and STOP
NRF_TWIM0->SHORTS = ((TWIM_SHORTS_LASTTX_STOP_Enabled << TWIM_SHORTS_LASTTX_STOP_Pos) & TWIM_SHORTS_LASTTX_STOP_Msk)
| ((TWIM_SHORTS_LASTRX_STOP_Enabled << TWIM_SHORTS_LASTRX_STOP_Pos) & TWIM_SHORTS_LASTRX_STOP_Msk);
//NRF_TWIM0->ENABLE = (TWI_ENABLE_ENABLE_Enabled << TWI_ENABLE_ENABLE_Pos) & TWI_ENABLE_ENABLE_Msk;
//There's a typo in nrf52_bitfields, so we set this manually.
NRF_TWIM0->ENABLE = (6 << TWI_ENABLE_ENABLE_Pos) & TWI_ENABLE_ENABLE_Msk;
}
void twi_tx(){
// clear the stopped event
NRF_TWIM0->EVENTS_STOPPED = 0;
// triggering the STARTTX task
NRF_TWIM0->TASKS_STARTTX = 1;
while( !(NRF_TWIM0->EVENTS_STOPPED) ){}
}
void twi_rx(){
// clear the stopped event
NRF_TWIM0->EVENTS_STOPPED = 0;
// trigger the STARTRX task
NRF_TWIM0->TASKS_STARTRX = 1;
while( !(NRF_TWIM0->EVENTS_STOPPED) ){}
}
void setup() {
twi_setup();
//Single TWI write to register 0x2A of value 0x3F
twi_set_cnts(2, 0);
txdata[0] = 0x2A;
txdata[1] = 0x3F;
twi_tx();
//Multiple TWI Write to registers 0x2A and 0x2B of values 0x00 and 0x01 respectively
twi_set_cnts(3, 0);
txdata[0] = 0x2A;
txdata[1] = 0x00; //high
txdata[2] = 0x01; //low
twi_tx();
//Single TWI Read at register 0x2A. Result shows up in rxdata[0]
twi_set_cnts(1, 1);
txdata[0] = 0x2A;
twi_tx();
twi_rx();
//Multiple TWI Read starting at register 0x2A. Results show up in rxdata[0],rxdata[1]
//untested
twi_set_cnts(1, 2);
txdata[0] = 0x2A;
twi_tx();
twi_rx();
}
void loop() {}