USB to TTL Serial Cable Problem

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jbielawa
 
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Joined: Tue Jul 22, 2014 9:23 pm

USB to TTL Serial Cable Problem

Post by jbielawa »

After spending a few hours trying to get my USB to TTL Serial Cable to work with a Raspberry Pi I have determined something is not quite right. Both screen and minicom freeze. The logs are showing a bunch of "failed to write -110" errors on Linux. On my Mac I am only getting an "unable to open device for configuration" message. I then checked the UART on the pi and have determined that it is in fact sending and receiving correctly. So then I checked the signals from the cable… I am getting a steady high level on the green wire from the time I plug it in. Is this a defective cable or am I missing something?

I have attached a picture of my connection. My Raspberry Pi is running Arch Linux. The remote computers I tried are running Arch Linux (up-to-date) and Mac OS X 10.7.5.
Connection to Raspberry Pi
Connection to Raspberry Pi
raspi_conn1.png (354.71 KiB) Viewed 228 times

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adafruit_support_mike
 
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Re: USB to TTL Serial Cable Problem

Post by adafruit_support_mike »

Try doing a loopback test: disconnect the cable from the RasPi entirely and run a jumper between the white and green plugs. That sends everything that goes out on the TX line back in on the RX line. If you can get access to the FTDI chip at all, what you type in a `screen` session should echo back immediately.

If you can't talk to the cable when the cable is only talking to itself, we'll call that a hardware failure.

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jbielawa
 
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Re: USB to TTL Serial Cable Problem

Post by jbielawa »

I tested it as you instructed and am still not getting anything... screen is just frozen until I disconnect the device.
Log Messages
Log Messages
Screen Shot 2014-07-23 at 7.02.44 AM.png (91.6 KiB) Viewed 207 times

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adafruit_support_mike
 
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Re: USB to TTL Serial Cable Problem

Post by adafruit_support_mike »

Sounds like a dead converter chip. Send a note to [email protected] with a link to this thread and the folks there will get you a replacement.

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jbielawa
 
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Re: USB to TTL Serial Cable Problem

Post by jbielawa »

I received my replacement cable today and it works perfectly! Thank you guys.

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