I’ve had a rash of problems with the touchscreens on bare Polarshields!

Over the last six months or so, I’ve noticed an issue where the touchscreen doesn’t work after booting. It looks ok, and updates fine, just no response to tapping.

I solve this by discharging the static from the device, while it is unplugged. I do it by either leaving it for a couple of minutes, unplugged, or by touching the metal USB socket housing, and rubbing an earthed piece of metal (it’s a wall-mounted shelving rack that I know happens to be screwed into the grounded metal studding in the wall). Handle it carefully, by the edges of the board while you’re plugging it back in.

I didn’t write anything about this until now, because until recently I was hoping this was a problem that only I was having! I think the touch IC must be being blocked during it’s boot process, or something like that.

I have handled hundreds of these, and the screens actually breaking down somehow is very rare. Having them rebel against their touch programming happens every day though, and I always fix it this way.

You can test your screen by using the UTFT and UTouch example sketches, but with these updated lines:

UTFT        myGLCD(TFT01_24_8, 38, 39, 40, 41);   
UTouch      myTouch(11, 12, 18, 19, 2);

Good luck!

Well, I’m glad you asked.

The drawing above is by Ben Young. I love it.

Released new code bundle. Only code change is that I’ve mended this line about how the crc_check pre-computed value table is defined in polargraph_server_polarshield.ino. The only purpose for this is to allow it to compile in the newest versions of the Arduino IDE (1.6x). If you aren’t using that version, you don’t need to update anything.

Also updated the UTFT library to v2.81, for the same reason (Arduino IDE 1.6 compatibility).

https://github.com/euphy/polargraphcontroller/releases/latest

I am generally filled with forboding about adding features to the Polargraph Controller. I remember it as being a twisted and unstructured wild-west kind of program. However, whenever I actually get into coding in it again, I always regret my fear, because I get something really useful done, in a really short length of time. Last weekend was no different.

Download the result: Polargraph v1.2 code bundle, or read on… If you dare.

G-Code importing

Polargraph exemplar Kongorilla has made a number of not-so-subtle hints about the impediments he runs into in getting stuff prepared for drawing. There’s a workflow that is sometimes fairly tortuous, even if it is logically straightforward. The controller has only been able to import SVG files, so a run through inkscape has always been the last step for most people.

The load vector dialog now allows .gco and .g files too, so anything that emits g-code files is also now a contender. Now, it’s fairly simplistic, understands only G0 and G1 commands, and the Z-axis implementation is rudimentary, but it does mean that it can swallow the output of wonderful things like Dullbits’ beautiful Death-To-Sharpie sketch.

The Z axis automatically makes a choice about when the pen is up or down. The very first Z axis change is ignored, and the second one is used henceforth as the “down” (drawing) position. Any position other than that second position is considered a travel (non-drawing_ position. This is because dullbits has Z1.0 as it’s drawing position and Z0 for travel, whereas inkscape(‘s gcodetools) seems to have Z-0.125000 as it’s drawing position, and moved to Z5.0 for travel. So opposite directions.

Usually the first Z movement is to shift into travel mode, in order to safely get to the start point, and then the second Z movement is to drop the pen / tool. Scripts that have funky stuff going on in their Z movement might need a bit of manual editing to work.

It’s immediately become obvious that .gco is not a standard enough file extension, so I’ll change it to .gcode as well for the next release. For now, just rename the file.

Preview cord offset

A commonly reported problem is that a drawing is short and fat, or tall and thin, or has a curved top or bottom, or it’s sides diverge.

There is a page about this in the Polargraph wiki, but it’s quite hard to diagnose, and hard to explain in words. I added this extra feature to the queue preview that allows me to simulate common calibration errors.

The way I imagine this being used, is:

1. Draw a shape. Oh no, it’s all wrong!
2. View the command queue in the controller app. It looks right here!
3. Adjust the preview cord offset until it the preview matches what happened on the paper.
4. Look at the value of preview cord offset. If it is:
   1. Positive: Your home point is further from the sprockets than you’ve told the machine. This might mean your home point is actually further down than you’ve measured, or your machine is wider than you’ve measured.
   2. Negative: Your home point is closer to the sprockets than you’ve told it. The home point might be higher up the machine than you have measured, or your machine is actually narrower than you’ve measured.

Firmwares

Polargraph_server_a1 has been updated to v1.2, and while there is no new functionality for UNO owners, I have merged the old MEGA-only features in, and made them configurable at compile time. So you can use polargraph_server_a1 on a MEGA, and get the SD card reading, norwegian pixel, spiral pixel etc. I actually fully expect this to have broken a load of stuff, so please take care, and report bugs.

In other news, I’ve also been working on porting the Controller to Processing 2, but that’s not borne fruit quite yet.

Download the code: Polargraph v1.2 code bundle