[34S] occasional RTC reset upon power on
03-21-2015, 10:32 PM
Post: #1
 John Galt Member Posts: 193 Joined: Oct 2014
[34S] occasional RTC reset upon power on
Occasionally, perhaps once every five or ten times I power up the 34S, there is a slight but noticeable pause (about a half second) before the display turns on. Normally, it's instantaneous.

If this pause occurs, the only noticeable effect is that the RTC is reset - time and date are reset to midnight, 1 January 2007. No other memories appear to be affected. "Restored" does not appear.

It does not seem to be related to how long the calculator was previously powered down, however I cannot seem to cause it to occur if I repeatedly turn it off and on.

It could be related to weak batteries. They're not new, but the battery indicator has not yet appeared.

The behavior is the same using either the mainline code build 3747 as well as Bit's custom version.

Any ideas?
03-21-2015, 11:22 PM (This post was last modified: 03-22-2015 02:38 AM by MarkHaysHarris777.)
Post: #2
 MarkHaysHarris777 Senior Member Posts: 333 Joined: Jan 2015
RE: [34S] occasional RTC reset upon power on
(03-21-2015 10:32 PM)John Galt Wrote:  Occasionally, perhaps once every five or ten times I power up the 34S, there is a slight but noticeable pause (about a half second) before the display turns on. . . .

It could be related to weak batteries. They're not new, but the battery indicator has not yet appeared.

Replace your batteries; took care of things when mine had the same symptom.

Power, Performance, Measurement

Delay at Power On

Cheers,
marcus

Kind regards,
marcus
03-22-2015, 02:39 AM
Post: #3
 MarkHaysHarris777 Senior Member Posts: 333 Joined: Jan 2015
RE: [34S] occasional RTC reset upon power on
hi John, see the links I updated on my previous post...

Kind regards,
marcus
03-22-2015, 03:00 AM
Post: #4
 John Galt Member Posts: 193 Joined: Oct 2014
RE: [34S] occasional RTC reset upon power on
Thank you Marcus. The symptoms are exactly as you described. I suspected it was due to marginal batteries, and that it might be related to this question.

It's also interesting to note that different battery manufacturers have different characteristics. The ones I'm using in this thread are from Maxell. The ones in the other are Panasonic. Whereas the Maxell voltage decreases gradually with use, the Panasonic voltage drops precipitously under load, only to recover significantly after the calculator shuts down.

Right now BATT shows the Maxell batteries at 2.8 V. That's low. The Panasonic might indicate 2.9 V, but under load that decreases suddenly, and in a manner that's obvious to the user (the calculator shuts down). I haven't been able to make the Maxell batteries crash under load while the calculator is in use. They appear to do so in a much less obvious way - the RTC reset. Or, a noticeable delay during power on.

The WP 34S is obviously very fast, even in SLOW mode. I wish there were a way to slow it down even more, to get more life out of the batteries or to provide more warning to the user that they're about to die. Perhaps CR2032 cells just weren't designed for the load it demands.

I just wish there were a better way of utilizing the low battery indicator... which is the subject of that other thread.
03-22-2015, 04:46 AM (This post was last modified: 03-22-2015 04:47 AM by MarkHaysHarris777.)
Post: #5
 MarkHaysHarris777 Senior Member Posts: 333 Joined: Jan 2015
RE: [34S] occasional RTC reset upon power on
(03-22-2015 03:00 AM)John Galt Wrote:  The WP 34S is obviously very fast, even in SLOW mode. I wish there were a way to slow it down even more, to get more life out of the batteries or to provide more warning to the user that they're about to die. Perhaps CR2032 cells just weren't designed for the load it demands.

I just wish there were a better way of utilizing the low battery indicator... which is the subject of that other thread.

hi John, ... that's why I pointed you to the link with the small code snippet. Tuck that snippet away someplace in the back of your WP34s (whatever I mean by that) and run it from time to time... set the counter to something meaningful... it should load the cpu briefly, but not run so long that IT kills the batteries!

When the batteries are getting weak the battery indicator will flicker a bit 'while' the nop loop is running, but before the batts are dead.

That's about all you can do. We might snoop through the code a bit (there may be more than just 'slow' and 'fast' on the Arm; Marcus would know the details. Maybe there's a way to cut the clock one more time?

As a side note: This is not for everyone (I'm not recommending this to anybody) but I am going to be modifying my WP34s with a docking station; IMHO its the best way to print, program, transfer peer-to-peer &c, and still have power. If all you need to do is peer-to-peer transfers then the micro stereo phone plug is the best way to go. But if you need the whole kit'n'kabootle then a docking station is the best way. Essentially, its a small box (cardboard works great) that runs a ribbon cable (six lines) into the back of the WP34s (with the back cover off, and the batteries removed) while the calculator sits on top. The cable plugs in via six pin header (completely concealed with the back cover on). The docking station has the IR diode(s), power pack (3v), transfer TxRx, and FTDI chip if desired. In my opinion NONE of that crap should be mounted in the 34s itself (there is not enough room, and the coin cells are not adequate for the job).

I do a lot of programming (constant looping) with my unit. My coin cells don't last long in that environment. They are fine for routine calculations, and some programming cycles; but not long running jobs... they just can't handle it.

Cheers,
marcus

Kind regards,
marcus
03-22-2015, 06:07 AM
Post: #6
 Paul Dale Senior Member Posts: 1,556 Joined: Dec 2013
RE: [34S] occasional RTC reset upon power on
(03-22-2015 04:46 AM)MarkHaysHarris777 Wrote:  That's about all you can do. We might snoop through the code a bit (there may be more than just 'slow' and 'fast' on the Arm; Marcus would know the details. Maybe there's a way to cut the clock one more time?

There are other clock speeds available. Marcus has used some of these already -- when you press a key the device kicks up to slow or fast speed depending on settings and the battery, when finished it slows to 32kHz for a while and then goes into power save mode, the saves lots of re-initialisation for a soon after keypress. We've had a couple of bugs where the 32kHz clock speed didn't kick up properly with another keystroke and the device was truly glacial. Marcus will, no doubt, correct me where I'm wrong

I'm not sure if there is a speed between 32kHz and slow however, the CPU datasheet would tell you. Also, remember the 34S firmware was not written with performance in mind. Accuracy & usability first and foremost, then code size.

Quote:As a side note: This is not for everyone (I'm not recommending this to anybody) but I am going to be modifying my WP34s with a docking station;.....

You could add some extra wires and include some of the other exposed stuff from the 30b's circuit board. There are some analogue to digital converters available, and one SPI bus is exposed (we considered SPI FRAM at one point). Not sure about I2C. These would require firmware changes, but folks seem to be getting the hang of these

- Pauli
03-22-2015, 12:14 PM (This post was last modified: 03-22-2015 12:15 PM by Marcus von Cube.)
Post: #7
 Marcus von Cube Senior Member Posts: 760 Joined: Dec 2013
RE: [34S] occasional RTC reset upon power on
There are plenty of options.

Code:
/// PLL MUL values. #define PLLMUL_HALF       599   // half speed (20 MHz) #define PLLMUL_HALF_NX    665   // if no crystal installed #define PLLMUL_FULL       1124  // (37 MHz) 1199 is probably too demanding on the hardware #define PLLMUL_FULL_NX    1249  // 1333  // no crystal

You can adjust these lines in main.c for different speeds. See set_speed() for details.

Marcus von Cube
Wehrheim, Germany
http://www.mvcsys.de
http://wp34s.sf.net
http://mvcsys.de/doc/basic-compare.html
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