Software – Page 61 – The Smell of Molten Projects in the Morning

Streaming Radio Player: RPi and OLED Updates

Because the OLED driver came from the pip package manager, not the Raspberry Pi’s system-level apt package manager, it (or they, there’s plenty of code under the hood) don’t get updated whenever I do system maintenance. The doc says this should do the trick:

sudo -H pip install --upgrade luma.oled

However, it turns out the new version has a slightly longer list of pre-requisite packages, causing the update to go toes-up at a missing package:

Could not import setuptools which is required to install from a source distribution.
Please install setuptools.

So update (or install, for the new ones) the missing pieces:

sudo apt-get install python-dev python-pip libfreetype6-dev libjpeg-dev build-essential

Doing so produced a backwards-compatibility error in my Python code:

... change ...
from luma.core.serial import spi
... into ...
from luma.core.interface.serial import spi

The motivation for all this fuffing and fawing came from watching some OLEDs wake up completely blank or become garbled in one way or another. Evidently, my slower-speed SPI tweak didn’t quite solve the problem, although it did reduce the frequency of failures. I have decided, as a matter of principle, to not embrace the garble.

Soooo, let’s see how shaking all the dice affects the situation.

It’s entirely possible the OLED controllers don’t quite meet their specs, of course, or have begun deteriorating for all the usual reasons.

2018-02-28

Streaming Radio Player: Standard Galactic Alphabet

Prompted by Jacob’s comment about the most recent OLED garble:

RPi Streaming Player - Standard Galactic Alphabet — RPi Streaming Player – Standard Galactic Alphabet

If ya can’t fix it, feature it!

That’s the First SGA Font from the Standard Galactic Font origin story. I copied the font file to one of the streamers, then re-aimed the font setup:

#font1 = ImageFont.truetype('/usr/share/fonts/truetype/dejavu/DejaVuSansMono.ttf',14)
font1 = ImageFont.truetype('/home/pi/sga.ttf',14)
#font2 = ImageFont.truetype('/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf',11)
font2 = ImageFont.truetype('/home/pi/sga.ttf',11)

It looks surprisingly good on such a low-res display.

The user community seems divided over the update … [grin]

2018-02-26

MPCNC: Autolevel Probe, Tactile Switch Edition

So I intended to shrink the Autolevel probe with 1/8 inch drill rod and a tactile membrane switch:

MPCNC - Simple Z probe - pogo tactile switch — MPCNC – Simple Z probe – pogo tactile switch

Unfortunately, it didn’t work nearly as well as I expected, because the switch membrane requires slightly less than the 180 g of pressure that pushes the P100 pogo pin entirely into its housing, leaving no overtravel worth mentioning. The membrane switch mechanism itself has much less than 1 mm of overtravel after the dome snaps, which left me with an uncomfortable feeling of impending doom.

I managed to figure that out before completely assembling the thing, saving me a bit of time.

The end of the pogo pin initially sported a dot of epoxy to spread the load over the switch dome:

I dismantled the pogo pin to see ~~whether I could substitute a more forceful spring~~ how it worked. As expected, a teeny spring drives the probe up against a trio of indentations in the brass housing. I didn’t expect the probe to have such an intricate shape, but it’s obvious in retrospect.

The OpenSCAD code for the housing required minimal tweakage from the larger version, so it’s not worth immortalizing.

2018-02-23

MPCNC: USB Camera Mount

The bCNC doc shows a camera mount made from acrylic and aluminum, but the MPCNC tool carrier lacks anywhere to secure such a thing. The camera should be reasonably close to the spindle axis, high enough to clear the work, and stable enough to hold its alignment. There’s a tiny flat spot next to the outer-lower Z-axis bearing supports (along the bottom of the picture), so that’s where it must go:

MPCNC - Central Assembly - detail — MPCNC – Central Assembly – detail

At least for now, anyway.

The USB camera originally mounted on a spring clip, with a 10 mm ball at the end of a 6 mm OD × 6 mm long stalk. Because we live in the future, building a matching ball socket isn’t particularly difficult:

MPCNC - USB Camera mount - Slic3r — MPCNC – USB Camera mount – Slic3r

3D printing FTW!

The stalk opening slants downward by 5°, because the camera PCB isn’t quite aligned with the stalk and I couldn’t get the first version to aim the lens directly downward.

A pair of brass inserts anchor the two M3 SHCS. The clamping force seems barely adequate to the task, but I’ll wait to see what else I don’t like before complexicating the situation.

A square of Genuine 3M sticky foam tape holds the mount to the MPCNC beside the DeWalt DW660 spindle:

MPCNC USB Camera - installed — MPCNC USB Camera – installed

The MPCNC bearing bracket doesn’t provide much surface area for the foam and it’s a bit more flexy than I’d like, but good practice probably requires verifying the spindle-to-camera offset before trusting the results, so we’ll see how it works.

The initial camera alignment consists of putting a mirror flat on the (pretty much level) platform:

MPCNC USB Camera - mirror alignment — MPCNC USB Camera – mirror alignment

Then you adjust the camera so its lens looks squarely at itself in the middle of the image:

bCNC - Camera - Mirror Alignment - first mount — bCNC – Camera – Mirror Alignment – first mount

The picture shows the camera aligned left-to-right (because the ball can rotate around the shaft axis), but the first mount didn’t allow the stalk to have enough downward tilt to center the lens image on the horizontal crosshair, thus the -5° tilt appearing in the second version.

With the camera lens centered on its reflection, you know the optical axis is perpendicular to the mirror. Because the mirror is flat on the bench, the optical axis must be perpendicular to the bench, which is parallel to the XY plane. Because we assume the MPCNC Z-axis moves perpendicular to the bench = XY plane, the distance between the spindle axis and the camera axis will remain constant, regardless of the Z-axis position.

Seems workable to me.

The OpenSCAD program as a GitHub Gist:

	// MPCNC USB Camera Mount
	// Ed Nisley KE4ZNU – 2018-02-16

	Layout = "Build"; // Build, Show, Mount

	/* [Extrusion] */

	ThreadThick = 0.25; // [0.20, 0.25]
	ThreadWidth = 0.40; // [0.40]

	/* [Hidden] */

	Protrusion = 0.1; // [0.01, 0.1]

	HoleWindage = 0.2;

	inch = 25.4;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

	ID = 0;
	OD = 1;
	LENGTH = 2;

	//- Adjust hole diameter to make the size come out right

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
	FixDia = Dia / cos(180/Sides);
	cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
	}

	//- Dimensions

	CameraStalk = [6.0 + 1.0,10.0 + HoleWindage,4.0]; // stalk OD, ball OD, stalk length
	CameraAngle = -5; // stalk tilt, negative = downward

	MountBlock = [24.0,20.0,CameraStalk[OD] + 7.0]; // cube to hold ball, stick to MPCNC frame

	Insert = [3.0,4.4,4.5]; // brass insert

	NumSides = 6*4;

	//—–
	// Define shapes

	// Camera mount, enlongated for E-Z differencing
	// Origin at center of ball, stalk along +X

	module Camera() {

	union() {
	sphere(d=CameraStalk[OD] + HoleWindage,$fn=NumSides);
	rotate([0,90 – CameraAngle,0])
	PolyCyl(CameraStalk[ID],3*CameraStalk[LENGTH],NumSides);
	}
	}


	module Mount(Half="All") {

	Rounding = 2.0;

	ZShift =
	(Half == "Upper") ? -MountBlock.z/2 :
	(Half == "Lower") ? MountBlock.z/2 :
	2*MountBlock.z;

	difference() {
	hull()
	for (i=[-1,1], j=[-1,1], k=[-1,1])
	translate([i(MountBlock.x – Rounding)/2,j(MountBlock.y – Rounding)/2,k*(MountBlock.z – Rounding)/2])
	sphere(d=Rounding,$fn=3*4);
	for (j=[-1,1])
	translate([-MountBlock.x/4,j*MountBlock.y/4,-(MountBlock.z/2 + Protrusion)]) {
	PolyCyl(Insert[OD],Insert[LENGTH] + Protrusion,6);
	PolyCyl(Insert[ID],2*MountBlock.z,6);
	}
	translate([MountBlock.x/2 – (CameraStalk[OD]/2 + CameraStalk[LENGTH]),0,0])
	Camera();
	translate([0,0,ZShift])
	cube([2MountBlock.x,2MountBlock.y,MountBlock.z],center=true);
	}
	}

	//—–
	// Build it

	if (Layout == "Mount")
	Mount();

	if (Layout == "Show")
	Mount();

	if (Layout == "Build") {
	translate([0,0.75*MountBlock.y,MountBlock.z/2])
	rotate([180,0,0])
	Mount("Upper");
	translate([0,-0.75*MountBlock.y,MountBlock.z/2])
	rotate([0,0,0])
	Mount("Lower");}

view raw USB Camera Mount.scad hosted with ❤ by GitHub

2018-02-22

MPCNC – Autolevel Probe, Collet Edition

Although putting a Z-axis height probe in a rigid pen holder worked well enough, it’d be handy to have a probe with a stud suitable for clamping in the DW660 spindle (with the power off!):

MPCNC - Z probe - DW660 - 0.25 collet — MPCNC – Z probe – DW660 – 0.25 collet

Inside, it uses the same pushbutton and pogo pin as the pen holder design, with a similar brass tube around the pogo pin.

There’s a conspicuous lack of good wire management; we all know where those wires will snap. In practice, you’d secure it to the DW660 power cord, way up on top, to eliminate most of the flexing. Still, it wants better strain relief than its gets from those heatstink tubes.

The solid model looks like a weaving shuttle:

MPCNC - Autolevel probe - collet - Slic3r preview — MPCNC – Autolevel probe – collet – Slic3r preview

It’s sitting upside-down in a 5 mm brim for more platform adhesion.

The next one will have a 1/8 inch stud to fit the DW660’s other collet and shorten the top by 3/8 inch, because I want the rod inserted three diameters for stability. The bottom can’t get much shorter, because the pogo pin determines the switch-to-tip distance. Maybe a simple membrane switch will work well enough?

You can see the depression in the glass sheet pretty clearly in a bCNC Autolevel scan on 30 mm centers (clicky for more dots):

bCNC - Probe Array - 600x390 30 mm OC - ISO2 — bCNC – Probe Array – 600×390 30 mm OC – ISO2

The OpenSCAD source code as a GitHub Gist:

	// MPCNC Z Axis Height Probe for router collet
	// Ed Nisley KE4ZNU – 2018-02-14

	Layout = "Build"; // Build, Show

	Section = false;

	/* [Extrusion] */

	ThreadThick = 0.25; // [0.20, 0.25]
	ThreadWidth = 0.40; // [0.40]

	/* [Hidden] */

	Protrusion = 0.1; // [0.01, 0.1]

	HoleWindage = 0.2;

	inch = 25.4;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

	ID = 0;
	OD = 1;
	LENGTH = 2;

	//- Adjust hole diameter to make the size come out right

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
	FixDia = Dia / cos(180/Sides);
	cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
	}

	/* [Switch] */

	SwitchBody = [7.8,6.8,7.0]; // PCB mount hardware extends infinitely to +Y
	SwitchButton = [3.5,5.0,1.0]; // OD allows some clearance
	SwitchClear = 5.0; // room for pad atop probe rod

	SwitchZ = SwitchBody.z + SwitchButton.z + SwitchClear;

	Sleeve = [1.5,2.5,15.0]; // tube around pogo pin

	ShankOD = 0.25 * inch; // rod into tool collet

	/* [Hidden] */

	WallThick = 3.0; // basic wall & floor thickness

	ProbeBody = [Sleeve[OD],
	2*WallThick + sqrt(pow(SwitchBody.x,2) + pow(SwitchBody.y,2)),
	3*ShankOD + SwitchZ + Sleeve[LENGTH]];

	echo(str("Probe Body: ",ProbeBody));

	NumSides = 2*4;

	//—–
	// Define shapes

	module Switch() {
	union() {
	translate([0,0,SwitchBody.z/2])
	cube(SwitchBody,center=true);
	translate([0,ProbeBody[OD]/2 – SwitchBody.y/2,(SwitchBody.z + SwitchButton.z)/2])
	cube([SwitchBody.x,ProbeBody[OD],SwitchBody.z + SwitchButton[LENGTH]],center=true);
	translate([0,0,SwitchBody.z])
	PolyCyl(SwitchButton[OD],SwitchButton[LENGTH] + SwitchClear,6);
	}
	}

	module ProbeHolder() {

	difference() {
	hull() {
	PolyCyl(Sleeve[OD] + 6*ThreadWidth,Protrusion,NumSides);
	translate([0,0,Sleeve.z])
	rotate(180/8)
	PolyCyl(ProbeBody[OD],SwitchZ,NumSides);
	translate([0,0,Sleeve.z + SwitchZ + 3*ShankOD – Protrusion])
	PolyCyl(ShankOD + 10*ThreadWidth,Protrusion,NumSides);
	}
	translate([0,0,SwitchZ + Sleeve[LENGTH]])
	rotate([0,180,0])
	Switch();
	translate([0,0,-Protrusion])
	PolyCyl(Sleeve[OD],Sleeve[LENGTH] + 2*Protrusion,NumSides);
	translate([0,0,Sleeve.z + SwitchZ – Protrusion])
	PolyCyl(ShankOD,3ShankOD + 2Protrusion,NumSides);
	if (Section)
	translate([ProbeBody[OD]/2,0,ProbeBody[LENGTH]/2])
	cube([ProbeBody[OD],2ProbeBody[OD],ProbeBody[LENGTH] + 2Protrusion],center=true);
	}

	}

	//—–
	// Build it

	if (Layout == "Show")
	ProbeHolder();

	if (Layout == "Build") {
	translate([0,0,ProbeBody.z])
	rotate([0,180,0])
	ProbeHolder();
	}

view raw Z Axis Height Probe – collet.scad hosted with ❤ by GitHub

2018-02-20

Streaming Radio Player: OLED Garble

Even in the dim light of dawn, it’s obvious slowing the SPI clock to 1 MHz didn’t quite solve the problem:

RPi OLED display - garbled — RPi OLED display – garbled

The display started up fine, became encrypted during the next few hours, and remained garbled as the track information changed. This is almost certainly a bad SPI transfer trashing the OLED module’s control registers.

Dropping the clock to the absolute minimum of 0.5 MHz didn’t help, either:

serial = spi(device=0,port=0,bus_speed_hz=500000)
device = sh1106(serial)

This particular display woke up blank after loading the new code, then worked OK after another reset. The other streamers lit up as expected on the first try, so the slower SPI isn’t making the situation instantly worse.

Running the clock at 1 MHz definitely reduced the failure rate, which suggests it’s a glitchy thing.

Good embedded systems practice suggests resetting the entire display from scratch every now and again, but my streamer code has no concept of elapsed time. Opening that particular can o’ worms would almost certainly result in an on-screen clock and I do not want to go there.

I suppose I must get a new oscilloscope with SPI bus decoding to verify all the SPI setup and hold times …

2018-02-19

Kinesis Freestyle2 Keyboard: Linux Fix

Someone who found my original post about the Freestyle2’s dysfunctional media keys came up with a fix: https://github.com/whereswaldon/kfreestyle2d.

Some notes for the next time this comes up:

After doing sudo modprobe uinput, lsmod | grep uinp returns nothing at all (Xubuntu 16.04), but evtest seems perfectly happy:

sudo evtest /dev/input/event17
Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x58f product 0x9410 version 0x0
Input device name: "KB800 Kinesis Freestyle"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 113 (KEY_MUTE)
    Event code 114 (KEY_VOLUMEDOWN)
    Event code 115 (KEY_VOLUMEUP)
    Event code 140 (KEY_CALC)
Properties:
Testing ... (interrupt to exit)
Event: time 1518199358.454619, type 1 (EV_KEY), code 113 (KEY_MUTE), value 1
Event: time 1518199358.454619, -------------- SYN_REPORT ------------
Event: time 1518199358.454638, type 1 (EV_KEY), code 113 (KEY_MUTE), value 0
Event: time 1518199358.454638, -------------- SYN_REPORT ------------
Event: time 1518199361.014681, type 1 (EV_KEY), code 114 (KEY_VOLUMEDOWN), value 1
Event: time 1518199361.014681, -------------- SYN_REPORT ------------
Event: time 1518199361.014699, type 1 (EV_KEY), code 114 (KEY_VOLUMEDOWN), value 0
Event: time 1518199361.014699, -------------- SYN_REPORT ------------
Event: time 1518199361.654701, type 1 (EV_KEY), code 115 (KEY_VOLUMEUP), value 1
Event: time 1518199361.654701, -------------- SYN_REPORT ------------
Event: time 1518199361.654721, type 1 (EV_KEY), code 115 (KEY_VOLUMEUP), value 0
Event: time 1518199361.654721, -------------- SYN_REPORT ------------
Event: time 1518199362.294715, type 1 (EV_KEY), code 140 (KEY_CALC), value 1
Event: time 1518199362.294715, -------------- SYN_REPORT ------------
Event: time 1518199362.294733, type 1 (EV_KEY), code 140 (KEY_CALC), value 0
Event: time 1518199362.294733, -------------- SYN_REPORT ------------

And the keys work without any special configuration on my part. Apparently they’re already built into XFCE, despite the sound keys not showing up in the Keyboard Shortcuts control panel where you assign programs to keys.

This is wonderful work!

I’ve never seen so many calculators before! Oops.

There should be some udev-rule-ish way to automagically figure out which /dev/hidraw? device to use and symlink to a suitable alias, so the program could use it without knowing the actual device. A casual search turns up:

https://unix.stackexchange.com/questions/105144/udev-rule-for-assigning-known-symlinks-for-identical-usb-serial-devices#105218

With which I’d produce /dev/input/kinesis0 and kinesis1, then use:

/home/ed/bin/kinesis/kfreestyle2d /dev/input/kinesis1

If only the Kinesis Fn key was momentary, rather than a push-on / push-off toggle. Le sigh. I can cope.

2018-02-16