First post, by rasteri
For various reasons I want to be able to stick a logic analyzer on the ISA bus, and watch (at a minimum) 8bits data + 8 bits address + IOW/IOR (18 signals). Unfortunately the logic analyzers that have more than 16 channels are a bit out of my price range and/or don't have fast enough I/O.
I spoke with reenigne who designed an awesomely simple device ( https://www.reenigne.org/blog/isa-bus-sniffer/ ) but it's aimed at lower-level analysis for emulator development and can't analyze all channels at once.
However, Cypress (now infineon) make a superspeed USB3 controller chip called the FX3, which has 32 channels and is available on a dev board for a reasonable price (£$€ 50). There is an FX3 firmware to turn it into a logic analyzer (https://github.com/zeldin/fx3lafw), as well as a fork of libsigrok with support for it ( https://github.com/zougloub/libsigrok-1/tree/ … fw-for-upstream ).
I built a little adapter board using some 74LVC245 buffers to shift everything down to 3.3v (only 24 channels for now because I ran out of buffer chips)
Currently I'm analyzing a PC/104 board as it's easier to probe. To test I wrote a Qbasic program to send incrementing values to port 80, and everything seems to be coming through very nicely.
In the future I may design a PCB to let the analyzer connect directly into an ISA slot but this will be more than enough for the testing I need to do at the moment.