Hello, I am trying to make VLF~LF sinusoidal frequency (10kHz ~ 50kHz) with NRF 52832.
My approach was making a square wave first, then putting the signal into the analog rectifier circuit.
First, I tried to make a square wave by using timer delay like the following,
while (1)
{
bsp_board_led_invert(3);
nrf_delay_ms(2);
}
and I thought it worked pretty well,
But since I request the NRF for another task, the signal has distorted like above in the middle of the signal.
Since I tried to make AM modulation/demodulation circuit with this wave, this was a huge problem for me.
I googled and found out I should approach with a timer interrupt.
So, I changed my code to the below.
int main(void)
{
bool erase_bonds = false;
log_init();
timers_init();
ble_stack_init();
gap_params_init();
gatt_init();
advertising_init();
conn_params_init();
peer_manager_init();
application_timers_start();
services_init();
sensor_simulator_init();
advertising_start(erase_bonds);
csense_initialize();
NRF_GPIO->DIRSET = 0x01 << 23;
timerInit(50);
while (1)
{
// bsp_board_led_invert(3);
// nrf_delay_ms(2);
if (NRF_LOG_PROCESS() == false)
{
power_manage();
NRF_LOG_FLUSH();
__WFI();
}
}
}
void timerInit(uint16_t period_us) // function for timer init
{
NRF_TIMER4->TASKS_STOP = 1; // stop the timer
NRF_TIMER4->TASKS_CLEAR = 1; // clear
NRF_TIMER4->MODE = TIMER_MODE_MODE_Timer; // set as timer mode
NRF_TIMER4->BITMODE = TIMER_BITMODE_BITMODE_32Bit; // timer counter as 32bit
NRF_TIMER4->PRESCALER = 1; //prescaler as 1
NRF_TIMER4->CC[0] = (float)8000000 * ((float)period_us / 1000000.0f);
NRF_TIMER4->INTENSET = 65536; // timer intrupt active
NRF_TIMER4->SHORTS = 0x01; // short cut register activate
NVIC_EnableIRQ(TIMER4_IRQn); // timer interupt function activate
NRF_TIMER4->TASKS_START = 1;
}
However, there were 2 problems.
One is I cannot adjust the period of the signal or duty cycle.
Even if I can adjust slightly for the pulse width, I cannot change the period of the signal.
And another problem is the resolution looks really bad even though the signal was not a high frequency.
I was able to see the fall time of the pulse.
Is there any way for me so I can make a clear sinusoidal (or square) wave by using NRF52832?
What could be the problem with my code?
