5 open source boards using the 74LS21
Real designs built with the 74LS21, from public GitHub projects: a quick way to see how others power, decouple and connect it. Each board comes with its KiCad files, full parts list and a render — and you can simulate its firmware on HardLabs.
MAXI030
aslak3
239.4 × 165.7 mm197 parts4LGPL-2.038- schematic only · 32 parts
Digicard-D-Net
markadev
32 parts2LNo license23 
Qx10 titan clone
brijohn
281 × 79 mm48 parts2LNo license9
Spreadout
239.4 × 165.7 mm190 parts4LGPL-2.038
IO board
cherry-takuan
99.7 × 99.7 mm36 parts2LCC-BY-SA-4.045
The 74LS21 in open source designs
The gallery holds 5 open source boards using the 74LS21 from 4 GitHub repositories; a typical one measures about 239.4 × 132.7 mm and carries around 48 components.
60% are two-layer designs, the rest use four layers or more, and 60% carry an open source license.
The most starred is IO board by cherry-takuan.
What boards using the 74LS21 are built for
74LS21: common questions
Where can I find a 74LS21 reference design?
Each of the 5 boards on this page is a real design using the 74LS21. Open one to see how it is wired up, with the full BOM, a render of the layout and links to its KiCad files.
What parts are used alongside the 74LS21?
The 74LS04, 74LS245 and 74LS74 appear in the most repositories here.
How big is a typical board using the 74LS21?
The median is 239.4 × 132.7 mm, and 60% are two-layer designs.
What is the most popular open source board using the 74LS21?
By GitHub stars, IO board by cherry-takuan, with 45 stars.
Can I simulate one of these boards using the 74LS21 before building it?
Yes. HardLabs turns a board's netlist and BOM into a working simulation, so you can boot and test firmware against it with no hardware on your desk.