Working with the Pumpkin MBM2


This document covers the KubOS Linux features which are specific to the Pumpkin MBM2 target.

Reference Documents

Pumpkin Documentation

The CubeSat Kit Motherboard Module (MBM) 2 reference document is available from Pumpkin and is a useful document for learning what each of the hardware components are and how they are connected.

Kubos Documentation

USB Connection

The Pumpkin MBM2 should be shipped with a USB Debug Adapter board.

The white connection cable should be plugged into the labeled “UART0” port on the edge of the board, with the exposed pins facing up.

The USB cable can then be plugged into your computer. Any required drivers should be automatically installed.

This connection will be passed through to a Kubos Vagrant image as /dev/FTDI and will be used for the serial console.


The Pumpkin MBM2 has several different ports available for interacting with peripheral devices. Currently, users should interact with these devices using the standard Linux functions. A Kubos HAL will be added in the future to abstract this process.


The Pumpkin MBM2 has 5 UART ports available for use in varying capacities:

Linux Device TX Pin RX Pin RTS Pin CTS Pin
/dev/ttyS1 H1.18 H1.17 H1.10 H1.9
/dev/ttyS2 H1.8 H1.7    
/dev/ttyS3 H1.5      
/dev/ttyS4 H1.16 H1.15    
/dev/ttyS5 H1.20 H1.19 H1.12 H1.11

Users can interact with these ports using Linux’s termios interface.

A tutorial on this interface can be found here


The Pumpkin MBM2 has one user-accessible I2C bus. Users can connect a new device to it via pins H1.43 (SCL) and H1.41 (SDA) of the CubeSat Kit Bus connectors.

I2C Standards Doc

KubOS Linux is currently configured to support the I2C standard-mode speed of 100kHz.

The I2C bus is available to the userspace as the ‘/dev/i2c-1’ device. Users will need to add their peripheral device to the system and then open the bus in order to communicate. Once communication is complete, the bus should be closed and the device definition should be removed.

Since the peripheral devices will be different for each client, they will need to be dynamically added in the userspace (method 4).

The bus is then opened using the standard Linux open function and used for communication with the standard write and read functions. These functions are described in the Linux I2C dev-interface doc. The buffer used in the write and read functions will most likely follow the common I2C structure of “{register, value}”

The user program should look something like this:

/* Add device to system */
system("echo i2cdevice 0x20 > /sys/bus/i2c/devices/i2c-1/new_device);

/* Open I2C bus */
file = open("/dev/i2c-1");

/* Configure I2C bus to point to desired slave */
ioctl(file, I2C_SLAVE, 0x20);

/* Start of communication logic */
buffer = {0x10, 0x34};
write(file, buffer, sizeof(buffer));

read(file, buffer, lengthToRead);
/* End of communication logic */

/* Close I2C bus */

/* Remove device */
system("echo 0x20 > /sys/bus/i2c/devices/i2c-1/delete_device);


The Pumpkin MBM2 has seven analog input pins available:

Name Pin
AIN0 H2.8
AIN1 H2.7
AIN2 H2.6
AIN3 H2.5
AIN4 H2.4
AIN5 H2.3
AIN6 H2.2

The pins are available through the Linux device /sys/bus/iio/devices/iio\:device0/.

A single raw output value can be read from each of the pins via /sys/bus/iio/devices/iio\:device0/in_voltage{n}_raw, where {n} corresponds to the AIN number of the pin.

Information about setting up continuous data gathering can be found in this guide from TI.

To convert the raw ADC value to a voltage, use this equation:

\[V_{in} = \frac{D * (2^n - 1)}{V_{ref}}\]


  • \(D\) = Raw ADC value
  • \(n\) = Number of ADC resolution bits
  • \(V_{ref}\) = Reference voltage

The Pumpkin MBM2 uses 12 resolution bits and a reference voltage of 1.8V, so the resulting equation is

\[V_{in} = \frac{D * (4095)}{1.8}\]


The CSK headers have 6 GPIO pins available for use. These pins can be dynamically controlled via the Linux GPIO Sysfs Interface for Userspace as long as they have not already been assigned to another peripheral.

CSK Pin Linux GPIO Value Direction
H1.6 65 Input
H2.18 61 Output
H2.21 89 Output
H2.22 87 Output
H2.23 86 Output
H2.24 85 Output

To interact with a pin, the user will first need to generate the pin’s device name:

$ echo {pin} > /sys/class/gpio/export

For example, to interact with pin H2.23 of the CSK header, which corresponds with GPIO_86, the user will use:

$ echo 86 > /sys/class/gpio/export

Once this command has been issued, the pin will be defined to the system as ‘/sys/class/gpio/gpio{pin}’. The user can then set and check the pins direction and value.

Set H2.23 as output:
$ echo out > /sys/class/gpio/gpio86/direction

Set GPIO_86's value to 1:
$ echo 1 > /sys/class/gpio/gpio86/value

Get GPIO_86's value:
$ cat /sys/class/gpio/gpio86/value


The GPIO direction should match the value in the above table

User Data Partitions

The Pumpkin MBM2 has multiple user data partitions available, one on each storage device.


The user partition on the eMMC device is used as the primary user data storage area. All system-related /home/ paths will reside here.


All user-created applications will be loaded into this folder during the kubos flash process. The directory is included in the system’s PATH, so applications can then be called directly from anywhere, without needing to know the full file path.


All user-created non-application files will be loaded into this folder during the kubos flash process. There is currently not a way to set a destination folder for the kubos flash command, so if a different endpoint directory is desired, the files will need to be manually moved.


All user-application initialization scripts live under this directory. The naming format is ‘S{run-level}{application}’.



This directory points to a partition on the microSD device included with the base Beaglebone Black board