Mats Engstrom

Should ECAD footprints rotate around pin 1 or on the footprint’s center?

Is this a stupid or really smart solution to keep the SD card inserted when you have a cheap socket? I lean heavily towards it's kinda smart, but it would probably be better to use a good socket with a proper ejection mechanism. ;-) From a reddit thread reddit.com/r/ElectroBOOM/…

A bit more progress on my discrete USB device. The red LEDs in the upper right corner shows the assigned USB ID. And the 7seg displays shows the first two (of eight) payload data bytes sent from my computer as a "vendor" specific packet. I think I can actually pull this off.

I don't spend as much time as I'd like on this discrete logic USB device, but now the packet type decoder and a reply sequencer are added and debugged. It can now capture the device address sent by the host during enumeration. This is only the rx, I hope to finish the tx as well.

Some of the ICs in my TTL stash have the top painted in silver color and black legends like the LS21 CERDIP here. Anyone have any guesses of why? Other cerdips of the same era and manufacturer are "normal".

Cool. I've been coding in C for decades but haven't come across this before. Grok tells me that likely() and unlikely() are similarly available in plain GCC C as well. I'll give it a try some day and see if it will improve execution times compared to the built-it prediction.

Dang! They shipped 65,000 of those at a price equivalent to $50,000 today. It ran BASIC in 1973 and had a CPU made out of discrete TTL logic. Wang 2200...

It took me a while to figure out why the current went up from 450mA to 950mA when I hooked up this card. Then I realized that those are 74S not 74LS. 😁 I probably should replace them if I can find a tube of the LS versions. But for the time being they'll have to do.

Not super happy with the PEOP (Pulsed End-Of-Packet) signal output it's just as long as the propagation of the 7474. The 7474 is reset fine to not-InPacket state, but the pulse might be too short for downstream logic. Maybe I should do the same as the PSOP logic for it...

They're virtually useless in practice. The rate of packets are far too high to see anything on them, but I thought that if I hooked up a USB host slowed down about 100 000 times it might look cool. Ofc I need even more LEDs sprinkled all over the design as well. ;-)

My discrete (no microcontroller/usb-chip) USB device is progressing. Top row=payload latches. Middle=bit counter/selector followed by packet storage. Bottom=buffer, clk+T-state, packet start/stop detect +NRZI decoder+bit stuffing detect. Now onto pkt decoding & reply sequencing.

While getting a few tubes of IC sockets I got some Global Specialties breadboards as well to try out and see if they live up to their reputation as being much better than the cheapos, but maybe not reaching 3M quality. If decent they're probably worth the $10 each.

Cool function, but.....

I can't really complain when I get 10 each of 3 different smaller PCBs made, taxed and shipped to me across the world in 14 days for $4.38 in total. Ok, I have to separate them myself, but at 0.8mm thickness just a few scores with a box cutter makes them breakable. @JLCPCB

This gave me an idea - imagine replacing the plastic here with heat resistant silicone and then just fill all the grooves with molten solder. Et voilà! And you'll have a fully connected PCB without a PCB ;-)

Simple design for a register used as a 1-hot counter. As long as nOC is asserted the pulls initialise the counter holding T0 high. When de-asserted it will count glitch free. Alternatively I could use a binary counter + a 3-to-8 decoder (non-inv) + a register. #offLabelUsage

Do you know the difference between the usual KB and a KiB? I must admit that I have to look it up each time I care about it.

The oscilloscope sure is colorful and pretty when all four channels are in use ;-) I'm currently debugging a part of my old long term project to make a USB device out of only 74LS series logic. The digital sim is working fine so now I've started the actual build. #summerProject