Beardy! Good to see you back. The interface for the LCD hasn't changed over the years, so you can replace it with another one that has the same 40 pin header.

The 2.2" screens kinda disappeared from the market, but I think I have a handful left. Otherwise the new 2.4" screens work ok too, with a rebuild of the firmware. Though they are getting more difficult to find too - the most modern ones use serial communications rather than the big-header parallel bus.

This resembles the screen I use:
http://www.elecfreaks.com/store/24-tft-lcd-tft0124-p-110.html
or
http://www.emartee.com/product/41969/

There is a minor difference between the different ones out there on the market, but they'll all work with a bit of (straightforward) modification to the firmware.

If you drop me an email (sandy dot noble at gmail.com) reminding me of your address, I'll send you a new 2.4" screen, or I can check for a 2.2" one if you'd prefer to keep it original 🙂

Lastly - there's been an issue with touchscreens not working recently. I haven't quite diagnosed the issue, but it seems to be a static-y kind of problem that prevents the touch IC from booting properly, or communicating properly. Or something like that.

This is only a problem for machines where your hands can touch the PCB, and proper grounding, with careful handling seems to bring it back to life. It's not broken, just malfunctioning. So not sure if that might be something to investigate.

sn

Seems only fair given how much I lifted the pen holder design off you in the first place!

Unless you've sent a "set home" first, nothing will do anything. "Set home" should engage the motors, and move-pen-to-point will do something once the motors are on, even if the machine isn't calibrated.

"move direct" might not work if the machine isn't sync'd with your controller properly. (Do an "upload machine spec" to sync.)

sn

Hi Sandy

Thanks for sending through the new screens, they just arrived. Yippee! Unfortunately, still no good, I tried the 2.2" screen first as that's a straight swap, no good, so I uploaded the latest 2.4" pre-compiled image and swapped to the 2.4" screen but still no dice. Any other ideas?

Sorry to be a continuing pain!

Hm, small progress, true, but it shows the thing physically works at least! Hurray. That kind of issue is typical of miscalibration of the touchscreen.

There's two things to change when defining the screen, you might already know this, but I'll say it anyway:

1) Define the screen type:
https://github.com/euphy/polargraph_server_polarshield/blob/master/polargraph_server_polarshield.ino#L58-L63

#define LCD_TYPE TFT01_24_8
or
#define LCD_TYPE ITDB22

2) Calibration details:
https://github.com/euphy/polargraph_server_polarshield/blob/master/polargraph_server_polarshield.ino#L31-L35
Calibration details go into UTouchCD.h. I think you've probably done both these things.

So just double-check those things. The calibration strings for the 2.2 screen and the 2.4 screen are in the file above.

There isn't much difference (electrically) between the version of polarshield you have vs the newest ones. The way the level shifting is done is a little different, but the outputs should be the same.

Actually, the new way of doing it (with buffers rather than resistors to drop the voltage from 5v to 3.3v) _was_ in response to some problems I was having with the LCD screens. In hindsight though, I've wondered if those problems were my regular static electricity problem - before I figured out they were static problems.

Sandy Noble

That it works ok for the calibration routine indicates that the polarshield is ok too - I believe that is true, and it's the rationale I've used.

I might try to do some more experiments around the timing of the init_touch stuff ... Because it is impossible to predict when the touch does work, and when it doesn't, it's really hard to do this kind of test.

You're probably right about the CAL_Z thing - where is the CAL_Z? Is it in the copy of UTouchCD.h that I've got in the code bundle?

Thanks for digging into this,
sn

I reckon if the thing works at all, then it's not an arduino _or_ a shield issue.

I know you've tried the calibration sketch, have you tried either of the other UTouch sample apps? There's a buttons one, and a paint one.

Oh yes, I see the CAL_S. Duh. Good spot.

sn

I'll try the other sample apps, but here's an update: I managed to get a set of calibration values that sorta worked - all the buttons worked if you hit the top right corner of them with a stylus. Huzzah! Trouble is, the unit doesn't respond to anything except pen lift/drop - which is the same as when controlling via usb, so it's beginning to look like it might well be a P-shield or Arduino issue. I'll update again when I've run the test apps.

I'm pretty puzzled about it. There's so little on the polarshield that actually does anything that I almost can't think what could be causing the issue. It's just resistors. And even more odd that it's something that changes over time - I mean it _used_ to work ok, but now it doesn't.

sn

Ha ha! Pulled it out the bag there 🙂

So anyway, that's weird. Some combination of configuration that we hadn't tried I guess?

sn