5 Jun
2009
5 Jun
'09
12:46 p.m.
One wonders if the in-house product test was more
rigorous than
connecting two devices with a 2m cable and sending a few characters at
9600 bps, or more likely, the engineers said that the design as given
wouldn't meet the formal spec without spending $0.25 on more robust
components and were told to keep it cheap since it would probably work
for most customers, or at least work well enough that few customers
would return the item.
Or, given that many people seem to have problems with RS232 interfaces
[1], they'd simply claim the cable was wired wrongly, or you haven't set
the baud rate/parity/word length correctly, or... And of coruse support
is non-existant, as it seems to be for all thigns these days :-(
[1] I don't seem to have too many problems. But then of course I don't
just wire the cable and hope, I read the manuals and more imporatantly
stick a breakout box or prootcol analyser on the devives first.
spikes at about 20kHz more like a sawtooth wave, than
nice neat pulses.
Is it possible that the DC-DC converter is playing up? I asusme this
USB-RS"32 converter is powered from the 5V on the USB port so presumably
it contains some kinde of DC-DC converter to get RS232 levels, possible
inside a MAXnnnn IC.Perhaps that can't supply enough current to the drivers.