FlexCase
MPU Pinout
Introduction
This guide is written as supplemental material for the FlexCase datasheet. Please reference the appropriate FlexCase datasheet (including revision) for the most accurate information.
| Type | Supported Modules (Label shortcode) |
|---|---|
| Recommended |
|
| Previously Validated |
|
| Supportable |
Any module which is compatible with the pinout defined by the Raspberry Pi CM4. Custom modules can also be supported.
|
**The CM3+ does not use hirose connectors, so each lookup has been grouped by function and the corresponding pin is listed beside the mux. lookup if the feature is available.
Pinout on FlexCases
The current available pins supported by FlexCases is provided below. Not all features listed here are available on every FlexCase. Check for a corresponding pin on the MCU for feature.

|
Hirose Pin |
Function | MPU Mux. Lookup |
|---|---|---|
| Control | ||
| HR J1-92 | Reset |
Controlled by MCU |
| HR J1-99 | Sleep | Controlled by MCU |
| HR J1-93 | Boot | Controlled by MCU |
| RS232 | ||
| HR J1-51 | RX |
|
| HR J1-55 | TX |
|
| MCU-MPU UART |
Use applicable pins depending on fashioned MPU. | |
| HR J1-28 | RPI RX | Rasberry Pi CM4 – GPIO13/RXD5 |
| HR J1-31 | RPI TX | Rasberry Pi CM4 – GPIO12/TXD5 |
| HR J1-62 | Radxa RX | Radxa CM3/CM3J/CM3I – UART5_RX_M0 |
| HR J1-57 | Radxa TX | Radxa CM3/CM3J/CM3I – UART5_TX_M0 |
|
MCU-MPU SPI |
MPU is typically master | |
| HR J1-40 | MISO |
|
| HR J1-44 | MOSI |
|
| HR J1-38 | CLK |
|
| HR J1-39 | CS0 (MCU CS) |
|
| HR J1-24 | (if available on FlexCase) RTC CS |
Controlled as Digital Output.
|
|
MCU-MPU GPIO |
||
| HR J1-48 | GPIO 0 (Request) |
Digital Input/Output. Typically used for request signals.
|
| HR J1-50 | GPIO 1 |
Digital Input/Output
|
| IoT | Airgain modems supported | |
| HR J1-26 | SKY STATUS |
Digital Input. Connected to Nimbelink pin 13 with a pull up. LOW is modem on, HIGH is modem off.
|
| HR J1-27 | SKY VCC EN |
Digital Output. Set HIGH to provide power to Nimbelink modem.
|
| HR J1-41 | SKY ON/OFF EN |
Digital Output. Set HIGH to turn on modem. Connected to Nimbelink pin 20.
|
| HR J1-45 | SKY VREF PWR |
Digital Output. Set HIGH to turn on modem. Connected to Nimbelink pin 14.
|
| HR J1-47 | SKY VUSB EN |
Digital Output. Set HIGH to enable USB on modem. Connected to Nimbelink pin 6.
|
| HR J1-49 | SKY RESET |
Digital Output. Set HIGH to reset modem. Connected to Nimbelink pin 5.
|
| HR J1-35 |
SKY DOUT (UART) |
MPU UART RX
|
| HR J1-36 |
SKY DIN (UART) |
MPU UART TX
|
| HR J1-58 |
SKY CTS (UART) |
MPU Clear to Send hardware flow control
|
| HR J1-56 |
SKY RTS (UART) |
MPU Request to Send hardware flow control
|
| HR J1-46 |
SKY DTR (UART) |
MPU Data terminal ready
|
|
Ethernet (Gigabit) |
Not present on all models | |
| HR J1-3 | ETH3+ | |
| HR J1-4 | ETH1+ | |
| HR J1-5 | ETH3- | |
| HR J1-6 | ETH1- | |
| HR J1-9 | ETH2- | |
| HR J1-10 | ETH0- | |
| HR J1-11 | ETH2+ | |
| HR J1-12 | ETH0+ | |
| Power | ||
| HR J1-77/79/81/83/85/87 | +5V0 | 5V0 input from main board |
| HR J1-78 | VREF | 3V3 reference from main board. |
| HR J1-84/86 | +3V3 | Not connected |
| HR J1-88/90 | +1V8 | Not connected |
| HR J1-(Several) | GND | All GND pins connected. |
| USB 2.0 | ||
| HR J2-101 | USB OTG |
Applicable Models
|
| HR J2-103 | USB D- |
Applicable Models
|
| HR J2-105 | USB D+ |
Applicable Models
|
| USB 3.0 | Not available on standard SKUs | |
| HR J3-(Several) | USB 3.0 |
Applicable Models
|