17 Jun
2013
17 Jun
'13
3:12 p.m.
> Most of the complexity is in the host, not the
peripheral. Indeed,
> even without the FTDI-style interface chips, it's still possible to
> inexpensively create a device-level interface to USB using nothing
> more than an AVR ATTiny MCU--
You can implementasync serial or IEEE388 in <20 MSI
chips.
That was my own reaction on seeing that, too - needing an entire CPU,
albeit a simple one, is being cited as evidence of how simple it is?!
Depending on what it's to be connected to, I could come pretty close to
an async serial interface using discrete transistors. I'd need a lot
of them, probably nearly a hundred by the time it's all done, but it's
not out of reach. USB probably _is_ out of reach.
And when things don't work, it's a lot harder
to make sense of the
signals on a USB cable than those on an RS232 or IEEE488 cable.
Dunno 488, never done much with that. But 232, yeah. Indeed, crank
the baud rate down to ca. 15 baud and a little practice lets you read
off character values by eye. Even at higher rates I've sometimes been
able to tell useful things by watching blinkenlights.
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