The symptom is that it will download data from my GPS only some of the time. Upon closer examination, it appears that it will sometimes drop the first character on a read.
I have a bit more data on this now.
I got my hands on another pl2303 adapter, which does not exhibit this problem. The problematic one is a "type 2" and the OK one is a "type 1"
The good one works great with the GPS.
For testing, I just shorted pins 2 and 3 on the adapter and ran a testing procedure.
I'm attaching a short script with he testing procedure. This procedure causes the problem to occur _every_ time. The good adapter shows
foofoofoofoofoofoo
[pause]
foofoofoofoofoofoo
and the bad one always shows foofoofoofoofoofoo [pause] oofoofoofoofoofoo
(note the dropped f)
Also of note: I got an oops and looping vm messages when I didn't wait one second after one of the fuser -k (see script below).
You can see the results of these two scripts at http://throb.netspace.org/~bperk/pl2303-type2.log (bad one) http://throb.netspace.org/~bperk/pl2303-type1.log (good one)
You can also see the diff -u good bad http://throb.netspace.org/~bperk/diffgoodbad.log
The testing script is at http://throb.netspace.org/~bperk/serialtest
but here it is also, with a few extra comments.
#!/bin/bash
fuser -k /dev/ttyUSB0 rm /tmp/tmplog # special log file for testing service syslog restart rmmod pl2303 modprobe pl2303 debug=1
echo Please insert bad adapter, the hit enter read foo stty -F /dev/ttyUSB0 -echo -echoe -echok -echoctl -echoke -onlcr 57600
cat /dev/ttyUSB0 & sleep 1; echo 'foofoofoofoofoofoo' > /dev/ttyUSB0 sleep 1; fuser -k /dev/ttyUSB0 sleep 1; #<crashed machine once without this line cat /dev/ttyUSB0 & sleep 1; echo 'foofoofoofoofoofoo' > /dev/ttyUSB0 sleep 1;
echo Please take out bad adapter, the hit enter read foo fuser -k /dev/ttyUSB0 cp /tmp/tmplog /tmp/badlog rm /tmp/tmplog service syslog restart rmmod pl2303 modprobe pl2303 debug=1
echo Please insert good adapter, the hit enter read foo stty -F /dev/ttyUSB0 -echo -echoe -echok -echoctl -echoke -onlcr 57600
cat /dev/ttyUSB0 & sleep 1; echo 'foofoofoofoofoofoo' > /dev/ttyUSB0 sleep 1; fuser -k /dev/ttyUSB0 sleep 1; cat /dev/ttyUSB0 & sleep 1; echo 'foofoofoofoofoofoo' > /dev/ttyUSB0 sleep 1;
echo Please take out good adapter, the hit enter read foo
fuser -k /dev/ttyUSB0 cp /tmp/tmplog /tmp/goodlog
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