On Thu, Mar 1, 2018 at 4:12 PM, Christopher Havel <[email protected]> wrote: > I /designed/ that circuitry in the micro-desktop. I still have the paper > copy somewhere...
Very nice! > You can also do it with a dedicated DAC chip, which is the > easy-but-expensive way I hinted at. > > But we aren't testing /that/ part -- the micro-desktop -- are we? If we're > testing the /card/, the card does not output anything remotely like VGA, > and, therefore, some kind of conversion is necessary in order to attach it > to a VGA cable as was being proposed in the email I replied to about that. We aren't planning to test the micro-desktop. The planning is for tests of the card mounted in a micro-desktop case to use as a test fixture. We are planning to use your good work on the micro-desktop case to our advantage and connect the VGA cable to the micro-desktop VGA connector in order to see that the EOMA68 RGBTTL (with EDID) works as advertised! > All you really need for this is a laptop PCMCIA or CardBus card cage, an > IDE cable or two, a couple 4051s and toggle switches on a slice of > perfboard, a 9v battery with connector and switch, and a cheap USB logic > analyzer attached to a laptop. You use the 4051s, switched manually, and > powered by the 9v battery, to act as input expanders for the logic > analyzer. Each 4015 turns one channel into eight and requires three "on-on" > switches -- with one "on" wired to +9v, one to ground, and the common to > the chip. You use the IDE cable for the wires ;) If you hook it up so that > you have one 4051 mux per logic analyzer channel, that'll give you 128 (!) > channels to switch with -- most USB logic analyzers, even the super cheap > ones, are 16-channel... > > Heck, if you wanted to make the circuit "complicated" -- I could draw up > something that automatically iterated through the channels for you at the > press of a single button, switching at variable speed with a pot, a 555, a > resistor and cap, and a couple 4017s and 4051s. You'd only need /one/ > channel for that -- so you could even use an o-scope there. Heck, I could > do it with that circuit and my old, old Tektronix 422... > > I'm honestly surprised that this sort of idea hasn't been mentioned yet. That is a cool way to set up a very wide logic analyzer. We were planning to use a little specialized hardware and less elbow grease to make our test fixture: * USB devices connected to the micro-desktop case USB ports, * SD peripheral connected to the micro SD slot, * VGA monitor connected to the VGA connector, * serial terminal connected to the UART pins in expansion header _______________________________________________ arm-netbook mailing list [email protected] http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook Send large attachments to [email protected]
