Archive for category Software
Homage Tek CC: Subscripts & Superscripts
Posted by Ed in Electronics Workbench, Software on 2020-02-04
The GCMC typeset() function converts UTF-8 text into a vector list, with Hershey vector fonts sufficing for most CNC projects. The fonts date back to the late 1960s and lack niceties such as superscripts, so the Homage Tektronix Circuit Computer scale legends have a simpler powers-of-ten notation:
Techies understand upward-pointing carets, but … ick.
After thinking it over, poking around in the GCMC source code, and sketching alternatives, I ruled out:
- Adding superscript glyphs to the font tables
- Writing a text parser with various formatting commands
- Doing anything smart
Because I don’t need very many superscripts, a trivial approach seemed feasible. Start by defining the size & position of the superscript characters:
SuperScale = 0.75; // superscript text size ratio
SuperOffset = [0mm,0.75 * LegendTextSize.y]; // ... baseline offsetHalf-size characters came out barely readable with 0.5 mm Pilot pens:
They’re legible and might be OK with a diamond drag point.
They work better at 3/4 scale:
Because superscripts only occur at the end of the scale legends, a truly nasty hack suffices:
function ArcLegendSuper(Text,Super,Radius,Angle,Orient) {
local tp = scale(typeset(Text,TextFont),LegendTextSize);
tp += scale(typeset(Super,TextFont),LegendTextSize * SuperScale) + SuperOffset + [tp[-1].x,0mm];
local tpa = ArcText(tp,[0mm,0mm],Radius,Angle,TEXT_CENTERED,Orient);
feedrate(TextSpeed);
engrave(tpa,TravelZ,EngraveZ);
}The SuperScale constant shrinks the superscript vectorlist, SuperOffset shifts it upward, and adding [tp[-1].x,0mm] glues it to the end of the normal-size vectorlist.
Yup, that nasty.
Creating the legends goes about like you’d expect:
ArcLegendSuper("pF - picofarad x10","-12",r,a,INWARD);Presenting “numeric” superscripts as text keeps the option open for putting non-numeric stuff up there, which seemed easier than guaranteeing YAGNI.
A similar hack works for subscripts:
With even more brutal code:
Sub_C = scale(typeset("C",TextFont),LegendTextSize * SubScale) + SubOffset;
<<< snippage >>>
tp = scale(typeset("←----- τ",TextFont),LegendTextSize);
tp += Sub_C + [tp[-1].x,0mm];
tp += scale(typeset(" Scale -----→",TextFont),LegendTextSize) + [tp[-1].x,0mm];The hackage satisfied the Pareto Principle, so I’ll declare victory and move on.
SK6812 RGBW Test Fixture: Row-by-Row Color Mods
Posted by Ed in Electronics Workbench, Software on 2020-01-28
The vacuum tube LED firmware subtracts the minimum value from the RGB channels of the SK6812 RGBW LEDs and displays it in the white channel, thereby reducing the PWM value of the RGB LEDs by their common “white” component. The main benefit is reducing the overall power by about two LEDs. More or less, kinda sorta.
I tweaked the SK6812 test fixture firmware to show how several variations of the basic RGB colors appear:
for (int col=0; col < NUMCOLS ; col++) { // for each column
byte Value[PIXELSIZE]; // figure first row colors
for (byte p=0; p < PIXELSIZE; p++) { // ... for each color in pixel
Value[p] = StepColor(p,-col*Pixels[p].TubePhase);
}
// just RGB
int row = 0;
uint32_t UniColor = strip.Color(Value[RED],Value[GREEN],Value[BLUE],0);
strip.setPixelColor(col + NUMCOLS*row++,UniColor);
byte MinWhite = min(min(Value[RED],Value[GREEN]),Value[BLUE]);
// only common white
UniColor = strip.Color(0,0,0,MinWhite);
strip.setPixelColor(col + NUMCOLS*row++,UniColor);
// RGB minus common white + white
UniColor = strip.Color(Value[RED]-MinWhite,Value[GREEN]-MinWhite,Value[BLUE]-MinWhite,MinWhite);
strip.setPixelColor(col + NUMCOLS*row++,UniColor);
// RGB minus common white
UniColor = strip.Color(Value[RED]-MinWhite,Value[GREEN]-MinWhite,Value[BLUE]-MinWhite,0);
strip.setPixelColor(col + NUMCOLS*row++,UniColor);
// inverse RGB
UniColor = strip.Color(255 - Value[RED],255 - Value[GREEN],255 - Value[BLUE],0);
strip.setPixelColor(col + NUMCOLS*row++,UniColor);Which looks like this:
The pure RGB colors appear along the bottom row, with the variations proceeding upward to the inverse RGB in the top row. The dust specks show it’s actually in focus.
The color variations seem easier to see without the diffuser:
The white LEDs are obviously “warm white”, which seems not to make much difference.
Putting a jumper from D2 to the adjacent (on an Nano, anyway) ground pin selects the original pattern, removing the jumper displays the modified pattern:
For whatever it’s worth, those LEDs have been running at full throttle for two years with zero failures!
The Arduino source code as a GitHub Gist:
LibreOffice Impress vs. NFS Network Shares vs. Caching
Whenever I put together a presentation, LibreOffice Impress gradually grinds to a halt with images in the slide thumbnails repeatedly updating and never stabilizing; eventually, LO crashes and sends a crash report to whoever’s watching. This may be due to my enthusiastic use of images to get my point(s) across, although I’m just not gonna back down from that position:
That’s a screenshot of a small thumbnail, enlarged for visibility, so it doesn’t look that crappy in real life.
Perhaps the problem arises because I insert the images as links, rather than embedding them to create a monolithic presentation file roughly the size of all outdoors?
Searching with the obvious keywords produces tantalizing hints concerning LO’s file locks clashing with NFS network share locking, which seems appropriate for my situation with all the files living on the grandiosely named file server (a headless Optiplex) in the basement.
The suggestions include making sure the NFS locking daemon is active, but I have NFC about how that might work in practice. The lockd daemon is running, for whatever that’s worth.
Seeing as how I’m the only one editing my LO presentations, disabling LO’s locks has little downside and requires tweaking one character in one line inside /usr/bin/libreoffice:
# file locking now enabled by default
SAL_ENABLE_FILE_LOCKING=0
export SAL_ENABLE_FILE_LOCKING
<<< blank line to show off underscores above >>>After a brief bout of good behavior, Impress resumed thrashing and stalling.
Copying the entire presentation + images to the SSD inside my desktop PC didn’t improve the situation.
More searches on less obvious keywords suggested disabling the Impress “background cache”, whatever that might be:
Tools → Options → Impress → General → SettingsThen un-check the ☐ Use background cache item, which may be the last vestige of the now-vanished memory usage and graphics cache size settings from previous versions.
In any event, disabling the cache had no effect, so it’s likely a problem deep inside LibreOffice where I cannot venture.
It autosaves every ten minutes and I must restart it maybe once an hour: survivable, but suboptimal.
There seems to be an improvement from Version 6.0.7 (Ubuntu 18.04 LTS) to Version 6.2.8 (Manjaro rolling release), although it’s too soon to tell whether it’s a fix or just different symptoms.
Raspberry Pi Shutdown / Start Button
Posted by Ed in Electronics Workbench, Software on 2020-01-23
While adding the usual Reset button to a Raspberry Pi destined for a Show-n-Tell with the HP 7475A plotter, I browsed through the latest dtoverlay README and found this welcome surprise:
Name: gpio-shutdown
Info: Initiates a shutdown when GPIO pin changes. The given GPIO pin
is configured as an input key that generates KEY_POWER events.
This event is handled by systemd-logind by initiating a
shutdown. Systemd versions older than 225 need an udev rule
enable listening to the input device:
ACTION!="REMOVE", SUBSYSTEM=="input", KERNEL=="event*", \
SUBSYSTEMS=="platform", DRIVERS=="gpio-keys", \
ATTRS{keys}=="116", TAG+="power-switch"
This overlay only handles shutdown. After shutdown, the system
can be powered up again by driving GPIO3 low. The default
configuration uses GPIO3 with a pullup, so if you connect a
button between GPIO3 and GND (pin 5 and 6 on the 40-pin header),
you get a shutdown and power-up button.
Load: dtoverlay=gpio-shutdown,<param>=<val>
Params: gpio_pin GPIO pin to trigger on (default 3)
active_low When this is 1 (active low), a falling
edge generates a key down event and a
rising edge generates a key up event.
When this is 0 (active high), this is
reversed. The default is 1 (active low).
gpio_pull Desired pull-up/down state (off, down, up)
Default is "up".
Note that the default pin (GPIO3) has an
external pullup.
debounce Specify the debounce interval in milliseconds
(default 100)So I added two lines to /boot/config.txt:
dtoverlay=gpio-shutdown
dtparam=act_led_trigger=heartbeatThe fancy “Moster heatsink” case doesn’t leave much room for wiring:
The switch button is slightly shorter than the acrylic sheet, so it’s recessed below the surface and requires a definite push to activate. It’s not as if it’ll get nudged by accident, but ya never know.
I’ll eventually migrate this change to all the RPi boxes around the house, because it just makes more sense than any of the alternatives. Heck, it’ll free up a key on the streaming radio player keypads, although I must move the I²C display to Bus 0 to avoid contention on Pin 3.
For reference, the Raspberry Pi header pinout:
I don’t know if I²C Bus 0 has the same 1.8 kΩ pullups as Bus 1, though; a look at the bus currents will be in order.
Homage Tek CC Cursor: Pivot Milling
Posted by Ed in Machine Shop, Software on 2020-01-22
A test to mill the pivot hole in 0.5 mm PETG sheet worked perfectly:
The cutter is a 3.175 mm = 1/8 inch router bit, one of a ten-pack that came with the CNC 3018 and to which I have no deep emotional attachment, held in a collet in the Sherline. The hole is 5.5 mm to fit an eyelet. The PETG is taped to a thin plywood scrap.
The hole happened by feeding G-Code manually into LinuxCNC, after touching off XYZ=0 at the center of the pivot and jogging up a bit:
g0 y-1.1625
f1000
g0 z0.5
g2 p5 z-1.5 i0 j1.1625Yes, I engraved the hairline using a diamond drag tool on the CNC 3018, cut the cursor outline with a drag knife on the MPCNC, then milled the pivot hole on the Sherline. This seems way over the top, even to me, but that’s just how the tooling worked out right now.
In actual practice, I’d probably mill a stack of cursors and pivot holes on the Sherline in one setup, then engrave the hairlines in a suitable fixture. I think I know enough to fit a spring-loaded diamond drag bit into the Sherline’s 10 mm ID spindle or, worst case, conjure a block for the Z-axis carrier in place of the entire spindle mount.
At least now I can remember what I did to make the hole.
HP 7475A Plotter Data Sniffing: socat Serial Port Tee
Some hints and examples provided the socat incantation required to sniff serial data between my Superformula demo program (on the Raspberry Pi) and my HP 7475A plotter:
socat /dev/ttyUSB0,raw,echo=0 SYSTEM:'tee /tmp/in.txt | socat - "PTY,link=/tmp/ttyv0,raw,echo=0,wait-slave" | tee /tmp/out.txt'The out.txt file collects data from the program to the plotter, the in.txt file holds data from the plotter to the program, and both files contain exactly and only the serial data, so some interpretation will be required.
With that in hand, tweak the .chiplotle/config.py file to aim Chiplotle at the virtual serial port:
serial_port_to_plotter_map = {'/tmp/ttyv0' : 'HP7475A'}This is dramatically easier than wiring a pair of additional hardware serial ports onto the RS-232 connection between the two:
The adapter stack instantly become a custom cable, although I miss Der Blinkenlights.
The HPGL output to the plotter (out.txt) comes from the Chiplotle driver with no embedded linefeed / carriage return characters, as HPGL uses semicolon command terminators, making it one humongous line impervious to the usual text utilities. In addition, several plotter configuration commands have prefix ESC (0x1b) characters without semicolon separators. Each LB (label) command within the stream ends with a 0x03 ETX character.
While one could fix all those gotchas with a sufficiently complex sed script, I manually separated the few lines I needed after each semicolon, then converted the raw ASCII control characters to displayable Unicode glyphs (␛ and ␃), making it legible for a presentation:
head -c 1000 out.txt
␛.B
␛.(;
IN;
OW;OW;OW;OW;
␛.H200:;
SC;
OW;OW;OW;OW;
IP0,0,16640,10365;
OW;OW;
SC-8320,8320,-5182,5182;
SI0.13,0.17;
VS8;
PA5320,-4282;
SP1;
PA5320,-4282;
LBStarted 2020-01-09 18:03:57.494617␃;
SP1;
PA5320,-4382;
LBPen 1: ␃;
SP1;
LBm=1.9 n1=0.71 n2=n3=0.26␃;
SP1;
PU;
PA8320.00,0.00;
PD;
PA8320.00,0.00,
6283.71,24.59,
5980.63,46.81,
5789.79,67.98,
5648.37,88.44,
5535.22,108.34,
5440.50,127.81,
5358.77,146.89,
<<< snippage >>>The corresponding responses from the plotter to the program (in.txt) are separated by carriage return characters (␍) with no linefeeds (␊), so the entire file piles up at the terminal’s left margin when displayed with the usual text tools. Again, manually splitting the output at the end of each line produces something useful:
1024
0,0,16640,10365
0,0,16640,10365
0,0,16640,10365
0,0,16640,10365
0,0,16640,10365
0,0,16640,10365
0,0,16640,10365
0,0,16640,10365
0,0,16640,10365
0,0,16640,10365
26
18
18
<<< snippage >>>The first number gives the size of the serial FIFO buffer. An inexplicable ten OW; commands from deep in the Chiplotle driver code return the Output Window size in plotter units. No other commands produce any output until the plot finishes, whereupon my code waits for a digitized point from the plotter, with the (decimal) 18 indicating a point isn’t ready.
All that at 9600 bits per second …
CNC 3018XL: Adding Run-Hold Switches
Posted by Ed in Electronics Workbench, Machine Shop, Software on 2020-01-03
Although the bCNC GUI has conspicuous Run / Hold buttons, it’s easier to poke a physical switch when you really really need a pause in the action or have finished a (manual) tool change. Rather than the separate button box I built for the frameless MPCNC, I designed a chunky switch holder for the CNC 3018XL’s gantry plate:
The original 15 mm screws were just slightly too short, so those are 20 mm stainless SHCS with washers.
The switches come from a long-ago surplus deal and have internal green and red LEDs. Their transparent cap shows what might be white plastic underneath:
I think you could pry the cap off and tuck a printed legend inside, but appropriate coloration should suffice:
Making yellow from red and green LEDs always seems like magic; in these buttons, red + green produces a creamy white. Separately, the light looks like what you get from red & green LEDs.
The solid model shows off the recesses around the LED caps, making their tops flush with the surface to prevent inadvertent pokery:
The smaller square holes through the block may require a bit of filing, particularly in the slightly rounded corners common to 3D printing, to get a firm press fit on the switch body. The model now has slightly larger holes which may require a dab of epoxy.
A multi-pack of RepRap-style printer wiring produced the cable, intended for a stepper motor and complete with a 4-pin Dupont socket housing installed on one end. I chopped the housing down to three pins, tucked the fourth wire into a single-pin housing, and plugged them into the CAMtool V3.3 board:
The CAMtool schematic matches the default GRBL pinout, which comes as no surprise:
The color code, such as it is:
- Black = common
- Red = +5 V
- Green = Run / Start (to match the LED)
- Blue = Hold (because it’s the only color left)
The cable goes into 4 mm spiral wrap for protection & neatness, with the end hot-melt glued into the block:
The model now includes the wiring channel between the two switches, which is so obviously necessary I can’t imagine why I didn’t include it. The recess on the top edge clears the leadscrew sticking slightly out of the gantry plate.
The LEDs require ballast resistors: 120 Ω for red and 100 Ω for green, producing about 15 mA in each LED. Those are 1/8 W film resistors; I briefly considered SMD resistors, but came to my senses just in time.
A layer of black duct tape finishes the bottom sufficiently for my simple needs.
Note: the CAMtool board doesn’t have enough +5 V pins, so add a row of +5 V pins just below the standard header. If you’ve been following along, you needed them when you installed the home switches:
A doodle giving relevant dimensions and layouts:
I originally planned to mount the switches on the other gantry plate and sketched them accordingly, but (fortunately) realized the stepper motor was in the way before actually printing anything.
The OpenSCAD source code as a GitHub Gist:
It seems bCNC doesn’t update its “Restart Spindle” message after a tool change when you poke the green button (instead of the GUI button), but that’s definitely in the nature of fine tuning.
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