XMEGA crystal 32 KHz is not working for RTC

Triplett · Joined: 28 Feb 2010 Posts: 52 Location: Maryland

Does anyone know why the real time clock is not working?

The code below works if either of the internal 32 KHz oscillators is selected.
I hope to use the 32 KHz crystal. Do I need to insert a bitwait somewhere?

Meister · Joined: 27 May 2010 Posts: 314

Could you post a code that works on internal oscillators and a code that doesn't work? (Maybe with a conditional compilation flag?)
I would test it on an XMega128A1 Xplained board that has the 32khz crystal on-board?

Triplett · Joined: 28 Feb 2010 Posts: 52 Location: Maryland

If curious to run it on a machine with no crystal, replace [Rtc = 1KHZ_32KHZ_CRYSTOSC] with [Rtc = 1KHZ_INT32KHZ_RCOSC]. Be sure to change the $regfile declaration to the correct XMEGA that you happen to be using, of course. It runs great with no crystal, but I want the 32 KHz crystal to work.

The board I am using has a 32 KHz crystal. It is a simple breakout board with an ATxmega32A4U. When using the breakout board, I have successfully activated the 32 KHz crystal as the RTC clock source in C, and it runs fine. It was straightforward. First, set bits in the XOSCCTRL register. Then, enable the oscillator using OSC.CTRL, and then finally do the C equivalent of a "bitwait" to see that the oscillator is ready and stable before moving on. I am wondering how to make these same things happen using the 32 KHz crystal in BASCOM.

It is probably something simple and, if you will excuse the pun, basic.

albertsm · Joined: 09 Apr 2004 Posts: 5024 Location: Holland

in your config osc, the 32KHZOSC=enabled is missing.

EDIT : that is for the internal 32 khz osc. so that is not the problem.

Meister · Joined: 27 May 2010 Posts: 314

This does not work:

albertsm · Joined: 09 Apr 2004 Posts: 5024 Location: Holland

i checked the PDF and all needed for the RTC to run is done by the selection.
Clk_rtcctrl is set, and Rtc_status.0 is checked for busy. after that the other regs are written.

so since Meister demos that it works, the problem is most likely not that the RTC does not work, but that the whole program will not work due to osc. config.

Triplett · Joined: 28 Feb 2010 Posts: 52 Location: Maryland

Very strange.

Meister's code doesn't work for me. Are we using the same processor? Mine is the ATXMEGA32A4U.
Could the 32 KHz external crystal work differently from one xmega to another?

Let's look at a simpler test case.

Scrap the code that also enables the external 16 MHz crystal oscillator.
Just run the processor on the default 2 MHz system clock.
Continue trying to make the RTC clock work using the 32 KHz crystal.

enniom · Joined: 20 Oct 2009 Posts: 472

Triplett · Joined: 28 Feb 2010 Posts: 52 Location: Maryland

We have a low-power application where nothing less than quartz timing accuracy will be sufficient. In the application, there will be conditions when the system will need to track time that has passed during a reduced power state where power consumption is kept as low as can be accomplished while tracking the elapsed time with quartz accuracy. Of course, this requirement can be met using an external low-power RTC that uses a watch crystal. It looks as if the function can be supported by the xmegas directly, so there should be no need to include an extra RTC module - if I can get it working.

For most users, the requirements would be different. It would be sufficient to use the internal RC oscillator for driving the RTC. Ours is not that case.

So, the mystery remains. In BASCOM, how is it possible to have the ATxmega32A4U RTC take its timing reference using the 32 KHz external crystal? I know it would be possible to resort to directly manipulating configuration registers, but I would prefer to avoid that, and apply BASCOM statements, if possible. I have been reading the data sheets. I can start experimenting with stuffing values into registers, and reading status bits. I am just not sure how to do that in the most elegant way using BASCOM. Any adult supervision would be greatly appreciated.

This is a bit of a tangent, but did anyone notice that in the simplified example, when I had disabled the internal 32 KHz RC oscillator, it still worked?

Meister · Joined: 27 May 2010 Posts: 314

@Triplett:

albertsm · Joined: 09 Apr 2004 Posts: 5024 Location: Holland

within series (A for example) all hardware is the same. That is why atmel/microchip has 1 manual for the series where everything is explained. And a generic datasheet for the chip.
The errata section for the 32U4 reveals some problems. just check with your revision.

The data sheet also shows that there are even 2 new modes which i did not noticed before. I will add those :
32.768 kHz from internal 32.768 kHz RC oscillator
External Clock from TOSC1

Did you add caps to the xtal?

beside problem with revisions of chips, it should not matter that Meister used a different chip. it is one from the same serie.
but exactly what kind of hardware do you use?

Triplett · Joined: 28 Feb 2010 Posts: 52 Location: Maryland

I do not understand caps. In the Config Clock, is the [Rtc = 1khz_32khz_crystosc] case sensitive?

The breakout board is from MattairTech, the MT-DB-X4. It is a good board, gold plated.

The datasheet is here:

http://www.mattairtech.com/docs/MT-DB-X4/MT-DB-X4_User_Guide.pdf

It would be easiest for us if I mark where all the jumpers are set.
I will attach a JPG of Justin's schematic with all jumper settings marked in green.
If a jumper has no green marking, it is open.

Triplett · Joined: 28 Feb 2010 Posts: 52 Location: Maryland

DUH

Capacitors are on crystal.

Shocked

MWS · Joined: 22 Aug 2009 Posts: 1803

albertsm · Joined: 09 Apr 2004 Posts: 5024 Location: Holland

caps is short for capacitor. i mean the ones from 6pf
i wonder which C code was able to run this when the jumpers are set the way you indicated?
IMO the jumpers do not route the xtal to the right pins. Have a look in the PDF of the processor.
The xtal pins are PR0 and PR1. you connect only the 16 mhz xtal.
but you must route the 32 KHz xtal to these pins.
I did not read the manual, but i guess there will be some instruction to set the jumpers to the 32 KHz xtal.
Do notice that this micro does not have 2 different osc. but you must make a choice. so either you use the 16 mhz as you have done now with the jumpers in green.
or you select the other one but then it runs on 32 khz.