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Connecting to the T-Mobile LTE-M Network

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Introduction

This document describes how to connect your IoT Developer Kit to T-Mobile's LTE-M network.

Prerequisites

  • A DevEdge Account. If you do not have one, please create one here.
  • The T-Mobile DevEdge IoT Developer Kit
  • A T-Mobile LTE-M SIM card
  • A computer with a web browser installed on it
  • A Wi-Fi Internet connection
  • A smartphone
    • If it is an iPhone
      • iOS version 15.3.1 and later installed on the iPhone.
      • The DevEdge IoT companion app installed on the iPhone.
    • If it is an Android
      • Android OS version 11 and later installed on the phone.
      • The DevEdge IoT companion app installed on the phone.

Configuration

Step A

Purchase the kit then activate it.

  1. Purchase the T-Mobile DevEdge IoT Developer Kit here.

    You must be logged into DevEdge to be able to order the kit.

  2. Go to the Dashboard page.

  3. Activate the kit by clicking Activate kit, Activate, then Done.

Step B

Power the kit on, install the DevEdge IoT app, then use your smartphone to confirm that you are connected to the T-Mobile LTE-M Network.

  1. Insert the SIM card included in the box into the IoT Developer Kit.

  2. Plug your IoT Developer Kit in like in the screenshot below.

  3. On your smartphone, install the DevEdge IoT companion app on either your iPhone or your Android device.

  4. Open the DevEdge IoT app then connect it to your IoT Developer Kit by tapping on "T-Mobile DevEdge".

  5. Confirm you are connected to the T-Mobile LTE-M network by looking at your DevEdge IoT companion app > Connectivity section.

Step C

Use the Web App to confirm that you are connected to the LTE-M network.

  1. On your computer, open a serial app like Tera Term, PuTTY, or Serial. For demonstration purposes we will use Serial on a Mac.

  2. Select the serial port that is connected to your IoT Developer Kit then click Open.

  3. Under Terminal > Settings > Line Settings > Baud Rate make sure the following values are set then click OK:

    1. Baud Rate / Speed - 9600
    2. Data Rate - 8
    3. Parity - None
    4. Stop Bits - 1

    5. Flow Control - None

  4. At the command line screen press Enter on your keyboard. The uart command prompt appears. To learn more about uart, please read the document Interacting with the Kit at CLI via tmo_shell.

  5. Enter tmo wifi connect 2 "<SSID>" 0 "<PSK>" to connect to Wi-Fi.

  6. Enter tmo json iface 2 to set the default interface that will send the developer kit's JSON payload then press Return on your keyboard.

  7. Enter fs cat /tmo/aws_session.txt then press Return on your keyboard.

  8. Write down the number that appears just before the uart command line. This number is your 8-digit access code to the web app.

    This access code is case sensitive. Please ensure that you get the spelling of this access code correct or it will not work in the web app.

    Also note that if you receive a "Failed to obtain file /tmo/aws_session.txt (err: -2)" please contact us and we will give you instructions on how to fix this error.


  9. Enter tmo json enable then press Return on your keyboard.

  10. You should receive a 200 status code.

  11. In a web browser, go to the web app https://devkit.devedge.t-mobile.com/.

  12. Enter the access code then click Next.

  13. Look at the LTE Signal Strength section to understand your T-Mobile LTE-M network connection.

  14. If your dBm is strong enough (-85 decibels or better) try sending yourself an SMS message. Learn more in the Interacting with the Kit at CLI via tmo_shell document.

    modem list
modem sms send <modem index> <phone number> <message>

Troubleshooting

  • Issue 1 - I inserted my SIM card, however, nothing is coming up on either the mobile app or the web app. What could be wrong?

  • Solution 1 - Your area may not have strong enough signal strength to connect to the T-Mobile LTE-M network. Please try moving to an area that does have strong enough signal strength (-85 decibels or better) and re-insert the card.


  • Issue 2 - I am seeing the following error in my serial app when my IoT Developer Kit boots up or is reset. What does this mean?
    <err> modem_cmd_handler: command AT+CIMI ret:-5
    <err> modem_murata_1sc: modem_cmd_handler_setup_cmds error

  • Solution 2 - This means that there is no SIM card inserted in the SIM slot. To fix this error, insert your T-Mobile SIM card into the SIM slot like in the screenshot below.


FAQ


  • Question 2 - I do not know my 8-digit access code that is used with the web app. Is there a way to retrieve it?

  • Answer 2 - Yes. In your serial app enter fs read /tmo/aws_session.txt. The output should give you your 8-digit code.