I was really surprised that there are people who hate receiving unsolicited advice, as this is how I learn many things. Social media should have an account setting by which users can declare whether or not they like unsolicited advice. Also there should be a setting by which I can prevent myself from replying to those who dislike unsolicited advice, so I won't inadvertently offend, and to hide their posts from me, so that I am not sad that they are having a problem that I know how to solve.

@whitequark What FPGA would you pick to make something similar to LibreVNA (design files and VHDL on GitHub), but with the possibility of avoiding proprietary FPGA tools? It looks like jankae used a xc6slx9. I guess it mostly reads from some ADCs into buffers and does DFTs. I've been vaguely considering making something like that but with different RF components, and. I don't want to pick a chip that locks me in to proprietary tools. I don't know much about recent FPGAs.

I built an optical receiver with a plastic optical fibre on its input and a USB UART on its output, and I can receive 4Mbps easily by pointing it at an ordinary indicator LED on a microcontroller board. (The USB UART drops some characters at this speed on both debian and win10, though it drops different ones on each OS. The hardware could do 12Mbps.) I wonder whether any popular devices actually do send data via their power-on LED.