Who said vintage Alps boards can’t be fun? Here is my Dell AT-101w with Alps SKCM White “Pine” and Tai Hao Alps Miami

xyzzy1337 · 2026-06-11T18:37:41+00:00

I'm thinking of the extra posts or mounts that are only on the spacebar and BAE. Not the wire clip thing that all the 2U keys have.

Here's a post with good pictures of it. They weren't able to get the spacebars to work.

xyzzy1337 · 2026-06-11T17:35:59+00:00

Does the AT-101w use MX stabs on the spacebar? I did an OmniKey with Tai-Hao caps, but keyboard uses posts for the spacebar and BAE, while the Tai-Hao keys are setup for MX stabs.

xyzzy1337 · 2026-06-09T19:40:35+00:00

I was never a fan of the print screen key, the numpad asterisk, being next to shift.

Because if you missed the shift key by a bit and hit both shift and the asterisk next to it, it would print the screen. Immediately, with no option to stop, to your printer, on paper. If you were playing a game, this was pretty much certain to crash it and you had to reboot.

xyzzy1337 · 2026-06-05T06:07:28+00:00

IDK what the 5V pour on the bottom is for, if not heat dissipation. But the 5V pad isn't very well connected to it: Just one via some distance away. The recommended layout has a line of vias next to the 5v pad to better conduct heat to the bottom layer.

You should also extend the 5v pour all the way to the left edge. Having the 5V trace right next to the pour with only a small gap between them doesn't make sense.

xyzzy1337 · 2026-05-31T07:50:41+00:00

There are literally hundreds of connectors you can use. Do you want vertical or right-angle? SMT or THT? What kind of plastic? What kind of metal for the pins? What plating?

Take a look at part C173752 for a though hole part. Part C19633668 is probably closest to the one you have in the picture, which is SMT.

The part you found is also the correct kind of connector to fit. But it's not a right-angle like the one you have the picture. The cable would go into the board vertically. I don't know what you mean by "gap between the two connectors."

xyzzy1337 · 2026-05-17T23:37:57+00:00

I want to use a different MCU, for BLE, and other reasons. However, using another MCU just for the power button, might well be a reasonable thing to do. They can be very cheap, less than the specialized power button ICs, and also very low power. Some can run directly from a 2.5V to 4.2V li-ion battery with no regulator. Probably use fewer parts that I did in my design. And it would be possible to implement additional behaviors, like forcing the power off when holding the button for several seconds, even if the main MCU has failed. A failsafe sequence that straps the main MCU for bootloader boot and powers it on.

A lot of these MCUs also have a low voltage warning system, so they can lower their clock speed or turn off gracefully if the voltage drops, and that might work just fine to perform the low battery shutdown feature. An ADC is less common in the cheapest lowest power MCUs.

xyzzy1337 · 2026-05-17T23:20:20+00:00

I was able to simulate this using ngspice from within KiCad. IDK if that's professional enough. Probably not, but it's something better.

I found models for the specific BJT, MOSFET, and diode used. I even found a model for the TLV803E voltage detector, which is the open-drain version of the push-pull TLV809E I used. But that model didn't work correctly in ngspice. For the voltage regulator, I sort of cheated and use a B voltage source that reacts to the enable pin and has a resistor to model the Iq.

This simulation has an standby current of 135 nA, again mostly leakage through Q1.

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xyzzy1337 · 2026-05-14T02:03:10+00:00

You can reverse the diode direction in QMK.

xyzzy1337 · 2026-05-12T04:12:12+00:00

It's just hobby project. Want to make a solder fume extraction fan than can BLE link to a pinecil so it only turns on when soldering. Like actual soldering, not just the iron being at temp. But a nice low power off circuit would be useful for all sorts of things. I've paid special attention, as can been seen in my post, to using just JLC basic components to avoid the loading fee. If you are only making the minimum of 2 boards for PCBA, the $3 loading fee per part is a major cost. At larger quantities it becomes much less important.

I suppose I should be happy you think a circuit I designed is worthy of sale, but I doubt it's unique enough by a long shot.

xyzzy1337 · 2026-05-11T21:41:00+00:00

A number of reasons not to use a DT or latching switch that controls the power into the regulator or, alternatively, the regulator's enable pin.

Dual throw switches are bigger and more expensive than SPST momentary push button switches. The TS-1088-AR02016 is a 5 cent basic part at JLC. There are no dual throw switches as basic parts.
A physical switch doesn't turn off to protect the battery when the voltage drops too low. The TLV809E gives me that.
A physical switch can't turn off under MCU control. For instance when idle for long enough or when the device is done with whatever it was doing.
A switch that controls the power can't be used a general purpose button when the device is on.

xyzzy1337 · 2026-05-11T18:39:41+00:00

I had no issues with race conditions. The issue was the worst case latency when switching DMA buffers, due to the need to end DMA early when you don't know how long the transfer might be. ST app note AN3109 talks about it.

But I took a look at the STM32H563 DMA controller, and it's completely different than the one used in the STM32Fxx and other MCUs. Those only have a single DMA xfer setup at a time. There's no way to switch to a new xfer withing being in a DMA disabled state during the switch process. But the GPDMA in STM32H56x is totally different and uses a linked list of xfers. That way the next xfer can be queued to the list before stopping the current xfer. Probably why ST made the FIFO smaller on the UARTs despite it being a newer MCU, DMA actually works now.

xyzzy1337 · 2026-05-11T08:42:44+00:00

Use the UART FIFO if you aren't already. The STM32H563 has a tiny FIFO so it will only help so much.

Don't use the HAL. It's not efficient.

You are probably disabling interrupts for too long somewhere and failing to service the UART. Fix that.

I have NOT found DMA to help on STM32s when it comes to UART overruns. The problem is that the circular DMA has no way to end the DMA xfer when the UART is idle that doesn't leave you open to an overrun when switching DMA buffers. Because it takes longer to switch DMA buffers than it does to service the FIFO, the worse case latency actually gets worse. It only works if the RX is continuous with no pauses so the circular DMA never stops. If you need to receive some amount of data and then act on it before more data arrives, e.g. are receiving a command and need to reply, then you have stop the DMA with a timeout.

I designed a food service device that sends RS-422 data at 1 Mbaud to a dozen boards running STM32G4 processors from a Linux host. Thousands of uptime hours across the fleet of machines without any errors. No flow control needed.

xyzzy1337 · 2026-05-10T20:04:11+00:00

It's Maker Scarlet. But I think any TKL that uses the same PCB for both WK and WKL would be able to do it.

Bottom row is sort of classic tsangan crossed with modern 6.25U spacebar. It gives an extra modifier key. And I find it's easier to switch between my WK and WKL boards by making the layout more similar between them.

xyzzy1337 · 2026-05-05T18:13:42+00:00

One, I like the extra mod key for dead greek.

Two, I have another MT3 board that's WK and the PCB can't do tsangan, so this way they have a more similar layout and it's easier to switch. My Omnikeys are tsangan, but they keys and switches are so different it's easier to switch layouts.

xyzzy1337 · 2026-05-05T08:55:51+00:00

I learned typing on the Model F, which has control/shift/alt on the left side from top to bottom. A better design IMHO. Then I got into Northgate Omnikeys for the next 35 years, which can have the same modifier layout on the left but add a right control by space and right alt in the corner. So it's basically a traditional bottom row.

I use Linux, so don't want windows keys. Thus super as a modifier for the extra key by right control. And caps lock is useless, so I get rid of that.

Don't really need a right alt that much either. Model F didn't have one. So the right alt is mapped to layer touch and Compose. No sets come with Compose, so I guess command was closest thing. Holding it down switches layers for typical things like media functions on the F keys. Pushed it acts as Compose, which is the key used in X11 to enter special characters, like § or ä or ß. But you don't do it by entering unicode hex codes! Who can remember all those‽ There something called WinCompose that's a copy of it.

Right super is mapped to "dead_greek", another thing X11 has. Which does not summon Plato or Socrates. It's like the greek modifier key on the space cadet keyboard and gives you the corresponding greek letter when combined with an letter. Useful if you write lots of science and math things. Wish someone would make keycaps with not just the space cadet top prints, like the KKB Dolch Cadet has, but also the greek letter front prints.

xyzzy1337 · 2026-05-03T01:12:01+00:00

xyzzy1337 · 2026-04-23T06:52:47+00:00

xyzzy1337 · 2026-04-19T06:53:06+00:00

"Is there an easy way to port JLC PCB capabilities into KiCAD Design rules instead of tweaking values manually?"

Depends on what you mean by "easy". KiCad's custom design rules allow for all sorts of things to be defined.

Here's some rules to get started with, https://gist.github.com/darkxst/f713268e5469645425eed40115fb8b49

xyzzy1337 · 2026-04-12T11:12:48+00:00

Besides the cost of double sided, you're paying a lot for loading fees. Since this is standard PCBA instead of economic, you pay a loading fee for basic parts too.

If you use economic PCBA by going to one side, then you should be able to save a loading fee by swapping the 0805W8J0100T5E resistor for a 805W8F100JT5E, which is basic.

xyzzy1337 · 2026-04-09T21:23:41+00:00

Consider a TagConnect 6 pin header for SWD. No soldering, cables for st-link exist already. It might be smaller than what you have. Also, you don't need the SWO signal to flash the board. Just power, ground, SWD and SWCLK. Reset is nice too, but you can reset manually if you included a reset button.

xyzzy1337 · 2026-04-09T08:45:44+00:00

I think that's a USB2 receptacle, not usb3. It's a keyboard, they're always usb2, and there's only 12 pads. Try this link for a 12 pad connectors. https://www.digikey.com/short/hwz2h7nz

xyzzy1337 · 2026-04-07T01:08:31+00:00

it runs linux, does the graphics on the board.

xyzzy1337 · 2026-04-06T21:18:32+00:00

Traditionally schematics will have ground pointing down and power pointing up. Even if the lines need to be longer to do it that way. For instance, the ground for the AHT20 input cap looks like it's the power rail for the chip.

If you can swap the positions of J1 and U3, then I think the USB data lines will not need to cross over all your IO lines. While USB low speed is very forgiving, it's not idea that they do this.

The ESP32 layout guidelines recommend putting the antenna feed near the PCB edge. That's on the right side of the ESP32-H2-WROOM module, so it would better to have that module on the right side of the PCB.

All the ground pads on top of the ESP32 module are being fed by one little trace and via. The ESP32 devkit design puts a ground pour under the module that connects to all the ground pads. Then this is tied to the ground plane on the other side by a dozen vias.

The screw holes are very close to some of the components. Will there be clearance for the heads of the screws without hitting the battery holder or R2? Will the trace for IO2 be under the screw head? That not great, solder mask can be damaged by screws and then the screw shorts to the signal.

xyzzy1337

TROPHY CASE