Low cost Logic Level Analyzer on Linux.

FT232R USB UART IC provides really cheap device, capable to sample about 10Mhz for 8 digital channels. This FTDI IC can be found on many embedded solutions like Arduino boards and many other development boards, primary acts as USB to serial UART converter. Another way to use this IC is Logic Signal Analyzer. Linux OS is required for control GUI and signal visualization / decoding. For this purpose install https://sigrok.org/wiki/PulseView developed by sigrok.

List of supported hardware can be found at this link: https://sigrok.org/wiki/Supported_hardware

For example connecting IR receiver, taken from old set-top box to the FTDI module permits infrared signal visualization from any TV remote controller.

FT232R datasheet: https://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf

IR receiver datasheet: https://www.vishay.com/docs/82491/tsop382.pdf

Find more details on Bit-Bang operating mode: https://hackaday.com/2009/09/22/introduction-to-ftdi-bitbang-mode/

Libftdi programming documentation: https://www.intra2net.com/en/developer/libftdi/documentation/

Python libftdi programming example: https://github.com/adafruit/Adafruit_Python_GPIO/blob/master/Adafruit_GPIO/FT232H.py

Arduino ATMega and PulseView solution works with 2Mhz or 4Mhz samplerate: https://github.com/gillham/logic_analyzer

More about Logic Sniffers: http://dangerousprototypes.com/docs/Open_Bench_Logic_Sniffer