Welcome to Microstack Node’s documentation!¶
Microstack Node (for Python) is the software component of Microstack which communicates with the Microstack I/O boards.
Contents:
Installation¶
First, make sure you have enabled I2C and SPI by running:
sudo raspi-config
and then navigating to:
Advanced Options > Would you like the I2C interface to be enabled? > Yes
Would you like the I2C kernel module to be loaded by default? > Yes
and:
Advanced Options > Would you like the SPI interface to be enabled? > Yes
Would you like the SPI kernel module to be loaded by default? > Yes
Then reboot.
You can install microstacknode with either apt-get or pip.
Installing with apt-get¶
Make sure you are using the lastest version of Raspbian:
$ sudo apt-get update && sudo apt-get upgrade
Install microstacknode for Python 3 with the following command:
$ sudo apt-get install python3-microstacknode
Installing with pip¶
Warning
Do not install microstacknode with both apt-get and pip as unexpected things will happen. Consider using virtual environments.
Make sure pip is installed:
sudo apt-get install python3-pip
Install microstacknode using pip:
sudo pip3 install microstacknode
GPS¶
The GPS uses the serial port. By default it is configured to output the login shell. You must disable this before GPS will work. To do so, run:
sudo raspi-config
Navigate to Advanced Options > Serial, disable the login shell
and then reboot.
Note
If you’re using a Raspberry Pi 3 you will also need to fix the
CPU core_freq at 250 otherwise the serial port baud rate
will not stay constant. To do this add core_freq=250 to
/boot/config.txt.
Testing¶
Accelerometer¶
Dump accelerometer data with:
$ python3 /usr/share/doc/python3-microstacknode/examples/accelcat.py
GPS¶
Dump GPS data:
$ python3 /usr/share/doc/python3-microstacknode/examples/gpscat.py
Other GPS Software¶
You might also want to install standard GPS software:
$ sudo apt-get install gpsd gpsd-clients python-gps
You can dump GPS data with:
$ sudo gpsd /dev/ttyAMA0 -F /var/run/gpsd.sock
or:
$ cgps -s
Replace /dev/ttyAMA0 with /dev/ttyS0 if you’re using a
Raspberry Pi 3.
Automatically Starting GPS¶
Reconfigure the GPS daemon and choose <yes> when asked if you want to start gpsd automatically (use the defaults for the remaining options):
$ sudo dpkg-reconfigure gpsd
Examples¶
L80 GPS¶
Note
It usually takes about two minutes for the GPS module to get a GPS fix (indicated by a red flashing LED on the GPS module). Until then, the L80GPS object may throw exceptions.
Note
Some commands may take one or more seconds to return. This is becasue
L80GPS reading the latest data from the serial port which the
GPS module is connected to. It only updates every second. It is
normal for locus_query_data to take a long time to return.
Todo
Link to GPS command wiki describing what each of the GP*** do.
Basic GPS (GPGLL is useful for location/time):
>>> import microstacknode.hardware.gps.l80gps
>>> gps = microstacknode.hardware.gps.l80gps.L80GPS() # creates a GPS object
>>> gps.get_gprmc() # get latest GPRMC data as a dictionary
>>> gps.get_gpvtg()
>>> gps.get_gpgga()
>>> gps.get_gpgsa()
>>> gps.get_gpgsv()
>>> gps.get_gpgll()
>>> gps.get_gptxt()
Extra modes:
>>> gps.standby()
>>> gps.always_locate()
>>> gps.sleep()
>>> gps.set_periodic_normal() # wakes from sleep or always locate off
LOCUS Data Logging¶
The GPS unit can log data to its internal memory without anything driving it using the LOCUS logging system. The following commands interface with LOCUS:
>>> gps.locus_query() # Query the status of the LOCUS logger
>>> gps.locus_start() # Start the logger
>>> gps.locus_stop() # Stop the logger
>>> gps.locus_erase() # Erase all data items in the log
>>> gps.locus_query_data() # Return a list of data items in the logger
For example, you could issue the following command:
>>> gps.locus_start()
Shutdown/halt the device running Python, go for a walk, reboot, start Python and then run the following command and receive GPS data for the walk:
>>> gps.locus_query_data()
The logger will continue to log GPS data until it runs out of memory, at which point it will stop. Manually stop the LOCUS logger with:
>>> gps.locus_stop()
MMA8452 Accelerometer¶
>>> import microstacknode.hardware.accelerometer.mma8452q
>>> accelerometer = microstacknode.hardware.accelerometer.mma8452q.MMA8452Q()
>>> accelerometer.open()
>>> accelerometer.get_xyz()
{'x': 0.00927734375, 'y': 0.00341796875, 'z': 0.49853515625}
>>> accelerometer.get_xyz(res12=False) # turn off 12-bit resolution
{'x': -0.0078125, 'y', -0.0078125, 'z': 0.5078125}
You don’t have to call open() if you’re using the with statement:
import time
from microstacknode.hardware.accelerometer.mma8452q import MMA8452Q
with MMA8452Q() as accelerometer:
while True:
print(accelerometer.get_xyz())
You can configure the range recorded by the accelerometer and change the output data rate (how fast the accelerometer is sampled):
import time
from microstacknode.hardware.accelerometer.mma8452q import MMA8452Q
with MMA8452Q() as accelerometer:
# change the settings
accelerometer.standby() # call standby before changing settings
accelerometer.set_g_range(2) # Either 2G, 4G or 8G
accelerometer.set_output_data_rate(800)
accelerometer.activate()
# let the accelerometer settle before reading again
time.sleep(0.5)
while True:
print(accelerometer.get_xyz())
SHT21 Temperature and Humidity Sensor¶
This behaves very similar to the accelerometer:
>>> from microstacknode.hardware.humiditytemperature.sht21 import SHT21
>>> sht21 = SHT21()
>>> sht21.open()
>>> sht21.get_humidity()
>>> sht21.get_temperature()
or even using with (Python-magic will call open()):
with SHT21() as htsensor:
while True:
humidity = htsensor.get_humidity()
temperature = htsensor.get_temperature()
print('Humidity: {:.2f} %RH'.format(humidity))
print('Temperature: {:.2f}°C'.format(temperature))
print()
time.sleep(1)
Reference: