cheap USB to serial adapters may be non-compliant (TTL)

I touched on this in this thread: [forums.reprap.org]

but there was a very interesting link today at Hack-a-day.

This guy put a scope on the cheap rs232<-->USB adapters and found that they're really not compliant. He found they were using +5 volts for high and 0 v. for low, in other words they were using TTL levels. Jan Axelson showed me how this *usually* works back in her series on the 8051 in ComputerCraft magazine back in the mid 90s.

So it looks like there may be another way around those $20 USB-to-Arduino cables.

(Incidentally this also explains why I've had a heck of a time using those dang adapters with some sensitive equipment.)

links:

[www.larsen-b.com]

[rambo.co.za]

It's a USB->RS232 TTL cable, It's specifically used in this way, RS232 drivers are a pain in the arse, the aim is to eliminate the full RS232 interface.

annodomini2 Wrote:
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> It's a USB->RS232 TTL cable, It's specifically
> used in this way, RS232 drivers are a pain in the
> arse, the aim is to eliminate the full RS232
> interface.

When I buy a cheap USB to RS232 Serial Port Adapter, it does not come from China with a label that says, "Sucks less than the other guy's, but we still don't implement the full RS-232 standard! 80% of the time it works out OK, and it's too cheap to return anyway!"

I'm ordering a few anyway. I'll add my own MAX232 and have a converter that works, all the time, with any hardware.