Working with the Pumpkin MBM2¶
Overview¶
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¶
- Getting Started with KubOS Linux and the Kubos SDK - Basic tutorial for creating your first KubOS Linux SDK project
- Using KubOS Linux - General guide for interacting with KubOS Linux
- KubOS Linux on Pumpkin MBM2 - Steps to build and load KubOS Linux for the Pumpkin MBM2
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.
Peripherals¶
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.
UART¶
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.
I2C¶
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.
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 */
close(file);
/* Remove device */
system("echo 0x20 > /sys/bus/i2c/devices/i2c-1/delete_device);
ADC¶
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:
Where:
- \(D\) = 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
GPIO¶
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
Note
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.
eMMC¶
The user partition on the eMMC device is used as the primary user data storage area. All system-related /home/ paths will reside here.
/home/usr/bin¶
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.
/home/usr/local/bin¶
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.
/home/etc/init.d¶
All user-application initialization scripts live under this directory. The naming format is ‘S{run-level}{application}’.