Searching For Documentation... NRF_TIMER4->MODE =

[GaryDT]

Good day to you,

I cannot find any reference/documentation whatsoever that relates to the following type of code... 4 lines of example code is below (from this link https://forum.arduino.cc/t/measuring-pulse-time-with-timers-gpiote-ppi-on-the-arduino-nano-33-ble-sense/699552)

NRF_TIMER4->MODE = TIMER_MODE_MODE_Timer;

NRF_TIMER4->TASKS_CLEAR = 1;

NRF_TIMER4->PRESCALER = 4; 

NRF_TIMER4->BITMODE = TIMER_BITMODE_BITMODE_16Bit;

From the above link you'll notice that it's related to Arduino, which I've been using so far, but I need to use/learn GPIOTE to achieve 1 micro second precision timing for generating PWM and PPM for servo control.

The above code sample's library is located within Arduino's installation folder structure, i.e., the sample is not directly dependent on Nordic's nRF5 SDK.

My question is... please can someone tell me where to find documentation that explains such instructions as those in the above example?

I'm using a Nano 33 BLE which itself uses a NRF52840

Like I say it'd be really great to get some help with this, thanks, Gary.

[Kazi Afroza Sultana]

Hello Gary,

Good day.

I can say you are trying to access the peripherals directly, so it's not really Arduino specific. You can look at this GPIOT tasks and events (GPIOTE) module Nordic Semiconductor Infocenter.  The GPIOTE module provides functionality for accessing GPIO pins using tasks and events. Form here you can know the functionality of registers. Its same for PWM and PPM. https://infocenter.nordicsemi.com/topic/ps_nrf52840/timer.html?cp=4_0_0_5_29_4#topic 

You also can look at this bare metal code example in github GitHub - andenore/NordicSnippets: Bare-metal examples for nRF51 and nRF52 .

Hope it helps. You can write us if you have further queries. 

Best Regards,

Kazi Afroza Sultana

[GaryDT]

That looks like exactly what I needed, and thank you, that really is a great help.

Final question if I may... specifically the NRF object syntax itself, i.e., "NRF_TIMER4" before the "->". I'm used to creating objects in C++ and creating/accessing data members and member functions of the class, and so with that in mind, I'd like to find where the object itself (or just simply a mention of it) is documented... "NRF_TIMER" syntax?

Thanks, Gary.

Edit: maybe all objects are prefixed with "NRF_"? but perhaps that's not it.

Update: I've been looking here under "Data Structures" and following the links infocenter.nordicsemi.com/index.jsp but I still haven't found reference specifically describing "NRF_TIMER0 or 1 2 3 4"

[Kazi Afroza Sultana]

Hello Gary,

These are the registers. If we consider NRF_TIMER4 (for example) , it is just a pointer to the HW register.   

...

You can see from the above table that the base address of TIMER4 is 0x4001B000. Its the peripheral and each register has an offset from that address.  These offset registers  (for example: TASKS_START, TASKS_STOP etc) are the address location added to the base address in order to get access to a specific address in terms of task pattern.

You can use these peripherals (TIMER0, TIMER1.. and so on) the way you use instances in C programing. Each time instance have their own address; but the offsets between individual registers are the same for all instances. 

You can see the Timer instances and offset registers here. https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf52840%2Ftimer.html&cp=4_0_0_5_29_4&anchor=topic ,

It is defined in nrf52840.h (nRF5_sdk_folder\modules\nrfx\mdk) file.

#define NRF_TIMER4 ((NRF_TIMER_Type*) NRF_TIMER4_BASE)

#define NRF_TIMER4_BASE 0x4001B000UL

Hope it helps.

BR

Kazi Afroza Sultana

[GaryDT]

Hi Kazi, that's the best answer anyone has ever given to me about anything, it really is...

Thank you so much 

[Kazi Afroza Sultana]

Hello Gary,

I am very glad to hear that. Thank you so much. We the support team  try to solve the problem at our best. 

Good luck.

Best Regards,

Kazi Afroza Sultana