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GMX-CARRIER

The GMX Carrier is a companion board for GMX modules.



It breakouts the GMX bus enabling quick prototyping of your next IoT module. But it doesn't stop here, the GMX Carries adds an USB/Serial bridge allowing the connection of the GMX serial port to your computer USB port. A LiPO battery section, including battery recharge when you connect the USB connector. Power ON/RESET/OFF pushbutton to turn on and off the module ( auto on is available with a jumper ). Last but not least an 10 pin ARM programming header that will enable the programming of GMX modules that have a programmanle MCU on board ( GMX-LR1 for example).

Here the back side of the board, with the label of the GMX bus breakout.



The carrier board has been designed for ultra low power nodes. When connected to the battery the overall power footpring of the module is around 3uA.

Board Jumpers

The carrier board has 4 jumpers that allow different behaviours.



  • A auto power on. When connected the board turns on automatically when power is applied. If removed you need to push the push button to turn on the board.
  • B handles the STM32 bootloader. When connected GMX modules that have an STM32 MCU (like the GMX-LR1) will enter bootloader mode.
  • C connects the Power On LED. Normally is not connected to save power.
  • D enables the step-up converter for 5V on the GMX bus, normally this voltage is not necessary, to save power it is recommended to keep it removed.

Connectors, Leds and Buttons

The board has a LiPO battery and an USB connector. The USB connection is used both to charge the LiPO battery - when charging the D1 green led will turn on and will go off when battery is charged - and to connect to the FTDI USB/Serial converter that connects to the GMX BUS serial port.
The push button S2 on the left of the battery connector can be used to turn on and turn off ( keep button pressed 5 seconds to turn off board) or to send a reset signal to the GMX BUS.
The red D2 LED will turn on - if the respective jumper is connected - when the board is powered.
Finally the P1 connector, which is an 10 pin ARM mini jtag (SWD) which can be used to program GMX Modules which support SWD programing.