Low-cost Wifi connected Wixel for use with xDrip. Can be used in combination with a Bluetooth Wixel.

This is a low-cost do-it-yourself Wifi connected receiver for the Dexcom G4 transmitter. It is intended to be used together with xDrip. It is possible to use multiple NodeMCU-Wixels to cover a large area. Can be used together with a Bluetooth Wixel, if you do not want to carray around the Bluetooth Wixel at home.

Example use

• A Wixel ~15 €
• A NodeMCU ~4 €
• A micro usb charger (An old phone charger works great.)
• A stripboard, perfboard or breadboard and cables depending on how it should be assembled.
• A box to put it in. (Optional)
• A Wifi network to connect the nodes too.
• An Android device (phone/tablet/computer)

Diagram

Finished NodeMCU-Wixel in box.

See bottom for more images.

1. Assemble the NodeMCU-Wixel by soldering or using a breadboard.
2. Download the NodeMCU-Wixel repository and extract the files.
3. Download the wixel-xDrip repository and extract the files.
4. Modify transmitter id in Wixel code from the NodeMCU-Wixel repository (NodeMCU-Wixel/Wixel/dexdrip.c) and set it to your transmitter id. Then save.
5. Copy dexdrip.c from the NodeMCU-Wixel repository (NodeMCU-Wixel/Wixel/dexdrip.c) to the wixel-xDrip repository (wixel-xDrip/apps/dexdrip/dexdrip.c).
6. Build the Wixel code in the wixel-xDrip repository and write it to the Wixel by following the instructions here.
7. Flash the NodeMCU with the firmware from the NodeMCU-Wixel repository (NodeMCU-Wixel/Firmware) using the NodeMCU Firmware Programmer.

• Connect the NodeMCU to the computer.
• Open the firmware programmer.
• In the Config tab:
  • Browse for the firmware file.
  • Make sure that the new firmware file is the only selected firmware.
  • Set Offset to 0x00000.
• In the Operation tab:
  • Select COM Port.
  • Click the Flash button.
• Wait for the flash to finish.

8. Change Wifi settings in the NodeMCU-Wixel repository (NodeMCU-Wixel/NodeMCU/modWifi.lua). Change ip, netmask, gateway, wifiSsid and wifiPassword depending on your network configuration. Then save. If you have multiple NodeMCU-Wixels, then make sure they each have a different ip.
9. Upload code to the NodeMCU using ESPlorer.

• Select COM port.
• Set Baud rate to 115200.
• Click Open.
• Make sure you are connected to the NodeMCU. You might need to press the reset button on the NodeMCU.
• Upload all files for the NodeMCU from the NodeMCU-Wixel repository (NodeMCU-Wixel/NodeMCU/) by clicking "Upload..." and selecting a file. Repeat until all files are uploaded.

10. Restart the NodeMCU by pressing the reset button on it.

• Wait until you see the text "Starting NodeMCU Wixel in 10 seconds...", then you know it is working.

11. Download and install xDrip to your Android device (phone/tablet/computer).
12. Start xDrip and goto Settings.

• Select "Wifi Wixel" as Hardware Data Source. (Or "Wifi Wixel + BT Wixel" if you also want to use a Bluetooth Wixel.)
• Under "List of recievers" enter the ip-addresses and ports of all NodeMCU-Wixels you want to use. This is the ip-address that was configured when changing Wifi settings for the NodeMCU-Wixel. The port is 50005 It should be a comma separated list. Example: 192.168.0.100:50005,192.168.0.101:50005

13. Select "Start Sensor" in xDrip and wait for two readings, then enter a dual calibration.

The LED, if present, will blink when an error occurs.

• Fast blink (on and off four times in one second): Unable to connect to access point. Wrong password, out of range, etc.
• Slow blink (on and off once in two seconds): Lost connection to access point, restarting after 60 seconds if not connected again.

Finished NodeMCU-Wixel in box.

Back of perfboard.

NodeMCU-Wixel connected on breadboard. No soldering needed.

Monitoring NodeMCU-Wixels.

This project relies on, and uses, the wixel-xDrip code and the xDrip application. A big thank you to the people behind these projects.