Hi, I want to use an NRF52805 with a voltage to frequency detector. If I understand the datasheet, there is one timer/counter and RTC on that chip. Is it possible to set the RTC as the timing gate, and use the T/C as an input pulse counter through the event system? I'm planning to use a single clock source (prob. 32MHz) and synthesize the LF clock required for the RTC from it.
I will be happy to know if this is a good way to go before fully adopting the hardware.
Cheers,
OK... following more replies I see that this IC should have 3 timer/counters and 2 RTCs. Can someone please confirm that 2 Timer/Counters can be configured, one as a gate and one as a pulse counter to perform this task?
Cheers
Hi
Indeed, the nRF52805 has 3 32-bit timers with counter mode and 2 RTCs available. If you see section 4.2.4 Instantiation in the product specification you can see what base addresses they use, so there should be no issues using two timers in your application.
Best regards,
Simon
OK, a few days with an NRF52-DK at hand I have a few more questions:
1. I see that there is a guy who did implement a counter similarly to what I want, using 2xtimers, events, tasks, and ppi here. I'm not 100% OK with the solution since: (a) the tasks of the counter and timer are both started from main. This does not guarantee a consistent timing for the counter and gate functions. (b) Likewise counter is read from a timer interrupt.
2. What i'd like to do is as follows: (a) Clear Timer0 -> (b) on Timer0 start generate event to start Counter1 -> (c) On Timer0 CC generate event to stop counter -> (d) on stop Counter1 generate event to stop Timer0
3. Can this be done? i.e. can I generate an event on Timer0 start and link it to Counter1 start? Also, can (d) be done? I have nothing against generating events (c) and (d) together from Timer0 CC with FORK if its easier.
4. I noticed that the ppi example that I attached above can't locate the required ENUMs, unless I add #include<hal/nrf_gpiote.h>. Should I use this piece of code? I am using VS code on NRF connect and had problems utilyzing the ADC when I inclused <hal/nrf_saadc.h>. If not, is there a good PPI/EVENT example for nrf connect?
Any help will be appreciated!
Matan
Hi
I don't see why what you describe can't be done at least, just make sure you mark the timers/counters with different priorities so they won't be conflicting with one another. The PPI example in the DevZone ticket you linked to is more than 6 years old at this point, and is therefore older than the nRF52805 altogether, so the SDK used there will not be compatible with your nRF52805. It's fine if you want to use the nRF5 SDK rather than the nRFConnect SDK, as the nRF52 series are supported by both, so it depends on what you want. You can see this statement on the state of the two SDKs.
If you decide to go for the nRF5 SDK, you will need to use a newer version (I recommend v17.1.0) but you can use the same principles explained by Susheel in the old thread if you find it helpful.
Best regards,
Simon
OK. I think I got the thing working, might be just good enough for my purpose:
1. I took the aforementioned example and made a simple change: I basically have gate start and end capture values for Timer1. These events trigger counter2 start/stop, respectively.
2. This way, the measurement is purely hardware. Result read is done in interrupt, but that doesn't really matter, as it's executed after count is done.
3. I'm attaching the example I've made if anyone is interested. It includes another pin that generates an output for testing (below). Tested on NRF-connect desktop, VS code, 1.9.0
4. For some reason, I'm only able to capture up to 2.66MHz (8/3). Any guess why? I can't see why it would be a hardware limitation, and supposedly nothing is done in software, but I'll have another look.
5. Regarding IDE. I'm very new to working with NRF products and I am EXTREMELY frustrated with the API. The samples are lacking, many samples don't support many boards, and the API has zero documentation. This results reverting mainly to NRF5-based examples which only add to the confusion. I hope that the IDE will become more friendly in the future.
/*
* Copyright (c) 2016 Intel Corporation
* Copyright (c) 2020 Nordic Semiconductor ASA
*
* SPDX-License-Identifier: Apache-2.0
*/
/**
* @file Sample app to demonstrate PWM.
*/
#include <zephyr.h>
#include <sys/printk.h>
#include <device.h>
#include <drivers/gpio.h>
#define TST_CLK_PIN 17 //this is led 0 pin on nrf52-dk
#define FREQ_MEASURE_PIN 11
void gpio_clock_8m(uint32_t pin_number)
{
NRF_TIMER0->PRESCALER = 0; // 16MHz
NRF_TIMER0->SHORTS = TIMER_SHORTS_COMPARE0_CLEAR_Msk;
NRF_TIMER0->CC[0] = 3; //1 for 16/2=8MHz for, 2 for 8/2=4MHz, 4 for 4/2=2MHz etc..
NRF_TIMER0->BITMODE = (TIMER_BITMODE_BITMODE_16Bit << TIMER_BITMODE_BITMODE_Pos);
//using config [1] since [0]
NRF_GPIOTE->CONFIG[1] = GPIOTE_CONFIG_MODE_Task | (pin_number << GPIOTE_CONFIG_PSEL_Pos) |
(GPIOTE_CONFIG_POLARITY_Toggle << GPIOTE_CONFIG_POLARITY_Pos);
/*Connect TIMER event to GPIOTE out task*/
NRF_PPI->CHEN |= 1 << 3;
*(&(NRF_PPI->CH3_EEP)) = (uint32_t) &NRF_TIMER0->EVENTS_COMPARE[0];
*(&(NRF_PPI->CH3_TEP)) = (uint32_t) &NRF_GPIOTE->TASKS_OUT[1];
NRF_PPI->CHENSET |= 1 << 3;
/*Starts clock signal*/
NRF_TIMER0->TASKS_START = 1;
}
static void timer_init() //gate timer
{
NRF_TIMER1->TASKS_STOP = 1; //trigger stop
NRF_TIMER1->MODE = TIMER_MODE_MODE_Timer; //mode timer
NRF_TIMER1->PRESCALER = 8; // Fhck / 2^8
//total gate time of timer 62500 - 1s
NRF_TIMER1->CC[0] = 62501; //end gate count
NRF_TIMER1->CC[1] = 1; //start gate count. don't start at 0 to no start on clear.
NRF_TIMER1->BITMODE = (TIMER_BITMODE_BITMODE_16Bit << TIMER_BITMODE_BITMODE_Pos);
NRF_TIMER1->TASKS_CLEAR = 1; //trigger zero timer
NRF_TIMER1->INTENSET = (TIMER_INTENSET_COMPARE0_Enabled << TIMER_INTENSET_COMPARE0_Pos); //interrupt on end gate count
NRF_TIMER1->EVENTS_COMPARE[0] = 0; //rest event flag for gate end
NRF_TIMER1->EVENTS_COMPARE[1] = 0; //rest event flag for gate start
}
static void counter_init() //actual counter
{
NRF_TIMER2->TASKS_STOP = 1; //trigger stop
NRF_TIMER2->MODE = TIMER_MODE_MODE_Counter; //counter
NRF_TIMER2->BITMODE = (TIMER_BITMODE_BITMODE_24Bit << TIMER_BITMODE_BITMODE_Pos);
NRF_TIMER2->TASKS_CLEAR = 1; //trigger zero counter
NRF_TIMER2->EVENTS_COMPARE[0] = 0; //reset event for compare
}
//counter input pin setting
static void gpiote_init(uint32_t pin)
{
NRF_GPIOTE->CONFIG[0] = 0x01 << 0; // MODE: Event
NRF_GPIOTE->CONFIG[0] |= pin << 8; // Pin number
NRF_GPIOTE->CONFIG[0] |= GPIOTE_CONFIG_POLARITY_LoToHi << 16; // Event rising edge
}
//hardware trigger: stop of counter on event of end timer1 gate
static void ppi_timer_stop_counter_init()
{
NRF_PPI->CHEN |= 1 << 2; //channel
*(&(NRF_PPI->CH2_EEP)) = (uint32_t)&NRF_TIMER1->EVENTS_COMPARE[0]; //attach end gate event
*(&(NRF_PPI->CH2_TEP)) = (uint32_t)&NRF_TIMER2->TASKS_STOP; //to counter stop trigger
NRF_PPI->CHENSET |= 1 << 2; //set channel
}
//hardware trigger: start of counter on event of begin timer1 (gate) event.gate
static void ppi_timer_start_counter_init()
{
NRF_PPI->CHEN |= 1 << 4;// channel
*(&(NRF_PPI->CH4_EEP)) = (uint32_t)&NRF_TIMER1->EVENTS_COMPARE[1]; //attach gate start event
*(&(NRF_PPI->CH4_TEP)) = (uint32_t)&NRF_TIMER2->TASKS_START; //to counter start trigger
NRF_PPI->CHENSET |= 1 << 4;
}
static void ppi_gpiote_counter_init()
//hardware attachment for the gpiote that was selected above
{
NRF_PPI->CHEN |= 1 << 1;
*(&(NRF_PPI->CH1_EEP)) = (uint32_t)&NRF_GPIOTE->EVENTS_IN[0]; //attach pin change
*(&(NRF_PPI->CH1_TEP)) = (uint32_t)&NRF_TIMER2->TASKS_COUNT;//to one count
NRF_PPI->CHENSET |= 1 << 1;
}
//gate end interrupt handler. Count is done at hardware and percice interrupt execution isnt critical
void TIMER1_IRQHandler(void)
{
if (NRF_TIMER1->EVENTS_COMPARE[0] != 0) //end gate event
{
NRF_TIMER1->EVENTS_COMPARE[0] = 0; //reset end gate flag
NRF_TIMER1->EVENTS_COMPARE[1] = 0; //reset start gate flag
NRF_TIMER2->TASKS_CAPTURE[0] = 1; //trigger get counter value
printk("cc: %dHz\n", NRF_TIMER2->CC[0]); //report to serial console
NRF_TIMER1->TASKS_CLEAR = 1; //reset timer
NRF_TIMER2->TASKS_CLEAR = 1; //reset counter
NRF_TIMER1->TASKS_START = 1; //start next count gate
}
}
void main(void)
{
NVIC_EnableIRQ(TIMER1_IRQn); //enable timer1 interrupt
IRQ_DIRECT_CONNECT(TIMER1_IRQn, 3, TIMER1_IRQHandler, 0); //link interrupt flag to handler
NVIC_SetPriority(TIMER1_IRQn, 3); //set interrupt execution priority
struct device *dev;//port container for gpio management
dev = device_get_binding("GPIO_0"); //on nrf52805 all GPIOs are on port0
/**/
gpio_pin_configure(dev, FREQ_MEASURE_PIN, GPIO_INPUT|GPIO_ACTIVE_HIGH|GPIO_PULL_DOWN); //p0.11 freq in
//init freq count hardware
counter_init();
timer_init();
gpiote_init(FREQ_MEASURE_PIN);
ppi_gpiote_counter_init();
ppi_timer_stop_counter_init();
ppi_timer_start_counter_init();
//test clock hardware
gpio_clock_8m(TST_CLK_PIN);
//start freq count task
NRF_TIMER1->TASKS_START = 1;
while (1) {
//manage loop
}
}
Thanks!