I am aware that using a USB Hub you can attach multiple arduino to one computer and either upload code one by one or use bash script to upload code on all arduinos together. But you can attach only as many arduino to a computer. I need to prgram around 100 arduinos/atmega ICs at once. Is there a way to do so? There are other methods that I found online like programming ICs over Wifi network. But that require a lot of WiFi chips connected to arduino. I cant setup that. Also that doesn't seems cost effective. Also Arduino sells their uno and other boards with pre-installed blink program. They must be doing batch programming only (multiple ICs at once). Any idea how they do this?
Arduino, the company, may sell on enough volume to make it worthwhile to get the microcontroller manufacturer to program the microcontrollers durin the production process This wouldn't cost them extra if they already get the bootloader pre-programmed. I've read programming ICs is a service available to high volume customers.
I guess low volume makers use fixtures that use the ICSP headers, pogo sticks or IC clips and which trigger the programming on contact using a microswitch etc.
I suspect Adafruit do something of this sort, see GIFs and video discussing testing at