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R. Pi cannot find FONA over Serial
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R. Pi cannot find FONA over Serial

by CPhillips7 on Tue Nov 06, 2018 4:19 pm

Hello,

I am working to connect a FONA to a raspberry pi 2 B+ with Raspian using the instructions found here:
https://learn.adafruit.com/fona-tetheri ... k/overview

The first issue I found was that the provided script to disable the kernel's use of the serial no longer works. The files it modifies do not exist on the latest Raspian distributions. Instead, I used raspi-config to disable the serial console (while leaving the GPIO serial turned on). I then connect the FONA as shown in the wiring diagram, and the FONA begins to blink as described in the instructions.

At this point I run into my problem. I cannot establish a serial connection with the FONA. Sending AT commands does not result in the FONA responding OK.

I have pointed the serial screen to ttyAMA0 and /dev/serial0. I have also tried different baud rates. To test my wiring connections, I have used multiple different bread boards as well as tying the FONA directly to the Pi with female-female wires. I am at a loss. Any ideas?

CPhillips7
 
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Re: R. Pi cannot find FONA over Serial

by adafruit_support_mike on Wed Nov 07, 2018 1:06 am

Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

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Re: R. Pi cannot find FONA over Serial

by CPhillips7 on Wed Nov 07, 2018 2:16 pm

I have uploaded pictures of my circuit. If anything is unclear, please ask. In the pictures, I am using a breadboard for photography's sake but have also tried direct connection. It is not clear in the photos, but the network light on the FONA is blinking.
Attachments
20181107_120605.jpg
The Pi
20181107_120605.jpg (168.93 KiB) Viewed 58 times
20181107_120555.jpg
The FONA
20181107_120555.jpg (176.58 KiB) Viewed 58 times
20181107_120546.jpg
Overview
20181107_120546.jpg (172.51 KiB) Viewed 58 times

CPhillips7
 
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Re: R. Pi cannot find FONA over Serial

by adafruit_support_mike on Thu Nov 08, 2018 3:46 am

Your soldering looks excellent and the connections seem to be right.

As a sanity check, try doing a loopback connection on the RasPi: move the jumpers so the RasPi's TX pin is connected to its RX pin, and neither are connected to the FONA, then try to use the RasPi's Serial interface. If everything works as it should, anything you send out on TX should come back on RX.

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Re: R. Pi cannot find FONA over Serial

by CPhillips7 on Thu Nov 08, 2018 3:53 pm

Thank you for your assistance. When I loop the Pi TX->RX I now see the AT command as I type it, but see no OK in response.

CPhillips7
 
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Re: R. Pi cannot find FONA over Serial

by adafruit_support_mike on Fri Nov 09, 2018 2:22 am

A loopback test doesn't show anything except what you type in. The RasPi is just listening to itself talk. The fact that you do see what goes out on TX coming back through RX means the RasPi's GPIO Serial connection is working properly and the jumpers are good.

That suggests the FONA's TX or RX pins have failed.

When did you get the FONA?

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Re: R. Pi cannot find FONA over Serial

by CPhillips7 on Fri Nov 09, 2018 12:29 pm

I received the FONA close to a year ago. I have also tested another FONA with identical setup. That one failed with the same issues.

CPhillips7
 
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Re: R. Pi cannot find FONA over Serial

by adafruit_support_mike on Sun Nov 11, 2018 2:17 am

I'm afraid a year is past our return/replace period, and the fact that you get the same behavior from another FONA suggests the problem might be between the two devices.

Try replacing the jumpers you're using, or moving the FONA to a different area on the breadboard. It's not unusual for breadboards to have flaky connections.

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Please be positive and constructive with your questions and comments.