Challenger RP2040 LTE Datasheet

The Challenger RP2040 LTE is a small embedded computer equipped with an LTE-modem in the popular Adafruit Feather form factor. It is based on an RP2040 microcontroller chip from the Raspberry Pi Foundation which is a dual-core Cortex M0 that can run on a clock up to 133MHz.

We paired the RP2040 with a 8MByte high speed flash capable of supplying data up to the max speed. The flash memory can be used both to store instructions for the microcontroller as well as data in a file system and having a file system available makes it easy to store data in a structured and easy to program approach.

The device can be powered from a Lithium Polymer battery connected through a standard 2.0mm connector. An internal battery charging circuit allows you to charge your battery safely and quickly. The device is shipped with a programming resistor that sets the charging current to 250mA. .

The LTE section of this board is based on UBlox LTE modem SARA R410M that is connected to the microcontroller through one of its internal UARTs.

The modem is controlled using standard AT-commands that allow the user to connect the device to a LTE network to send and receive data

Challenger RP2040 LTE

Short introduction to the board

PCB
The board is based on a popular form factor called “Feather” which is created and maintained by an American company called Adafruit. The entire specification for the Feather format is available here. The size of the PCB for the module is 50.80mm x 22.86mm but the entire module is a little bit bigger as the Type C USB connector protrudes about 1 mm outside the board.

Antenna
On the opposite end from the USB connector there is a small U,FL connector where an LTE antenna should be connected. The antenna must have 50 ohm impedance and should be mounted according to the manufacturer’s specifications.

Headers
On each of the longer sides of the PCB there are holes intended for soldering pin header connectors. If you don’t want to use connectors for some reason you can also solder a wire directly into the hole, making a permanent connection to your external device. If you go this way please make sure that the wires are fixed in place, otherwise, vibrations can cause the wire to break at the soldering point.

LED’s
On each side of the USB connector there is a small indicator LED placed. The LED which is marked CHG is the charge control indicator. This red LED will shine whenever the connected battery is being charged, and when the battery is fully charged the LED will turn off again. If you haven’t connected a battery to the board this LED will not come on at all.

On the other side of the USB connector there is a user-programmable green LED. This LED is connected to pin D15 and can easily be controlled by the user program.

Hardware details

Pins

The on board micro controller (RP2040) have a number of communication channels that have been routed out to the side (header connector) connectors.

  • UART – One UART channel have been routed to the header pins (RX, TX). The micro controller have 2 UARTs, on this board the second UART is used for communicating with the LTE modem.
  • SPI – One SPI channel have been routed to the header pins (SCK, SDO, SDI).
  • I2C – One I2C channel have been routed to the header pins (SCL, SDA).
  • Analog pins – The micro controller have 4 analog input pins that all are available on the header pins (A0-A3).
  • PWM – All pins can be used for PWM.

The pin chart below shows the placement of all pins and their respective functions. When working in an Arduino environment (or Platform IO) use the blue pins when writing your code and when working with CircuitPython use the orange marked pin assignments.

Power

The board can be powered from multiple sources. The most obvious way to run the board is by plugging it in to a USB cable and attach it to your computer. In this mode you can write software and test the board with all its functionality.

There is also a third way to supply the board. This way is more invasive and will disable the onboard 3.3V power regulator.

You will have to pull the EN header pin low and then supply your own 3.3V voltage on the 3.3V header pin. Please note that when disabling the onboard power regulator you will have to supply the 3.3V also when running the system on battery power.

Battery

As described earlier the board can be powered from a LiPo battery. The battery can be connected using a standard 2.0mm JST connector through the battery connector on the right side of the board or ff the battery is an integral part of the system that you are designing it is possible to connect the battery through the BAT pin instead.

Switching between the battery voltage and the applied USB voltage or external 5V is done seamlessly by the onboard circuitry.

Charging of the battery is done by either connecting a USB cable or by connecting a 5V power source to the header pin marked USB on the board. If you do this make sure you connect your voltage through a 1A Schottky diode to avoid any excessive current draw in the system when the two levels are slightly different.

Please note that providing external charger circuitry could destroy the internal charger on the Challenger board.

Connection between MCU and SARA R410M.

The board uses the second UART (UART 1) of the MCU to connect to the LTE modem. In addition to the RXD and TXD signals the RTS and CTS signals are also connected to support large data transfers. Three more GPIO pins are connected to the power on and reset pin of the device.

  • GPIO4 acts as UART1 TXD
  • GPIO5 acts as UART1 RXD
  • GPIO6 acts as UART1 CTS
  • GPIO7 acts as UART1 RTS
  • GPIO13 is connected the power on signal of the SARA R410M module.
  • GPIO14 is connected to the reset signal of the SARA R410M module.
  • GPIO15 is connected to the LDO that supplies the modem with power.


DescriptionValueComment
Board Size50,80 mm x 22,86 mm x 3,20 mmUSB Connector protrudes ~1mm outside PCB
Main micro controllerRP2040 from Raspberry Pi133MHz dual core Cortex M0
SPIOne SPI channel configured
I2COne I2C channel configured
UARTOne UART channel configuredSecond UART is for the LTE modem
Analog inputs4 analog input channels
LTE ModuleSARA R410MCat M1/NB-IoT
FLASH Memory8MByte 133 MHz
SRAM Memory264KByteDivided into 6 banks
USB 2.0 controllerUp to 12MBit/s full speedIntegrated USB 1.1 PHY
JST Battery connector2.0mm pitch
On board LiPo charger250mA standard charge current
Technical Data