A POC for a robotic vehicle on Rasperry Pi Zero and Python
There are two subprojects that have been developed herein:
- rover - a four-wheeled vehicle
- robby - a 2DOF robot arm
The vehicle was developed first. The intention was kind of to include a camera that could be robotically pan and tilted to survey the current location of the vehicle and in the future provide CV to navigate the vehicle.
The vehicle was developed first. The intention was kind of to include a camera that could be robotically pan and tilted to survey the current location of the vehicle and in the future provide CV to navigate the vehicle.
These aims diverged a bit and this repo is a bit mixed up.
- Raspberry Pi Zero W V1.1
- Kingston SDC4/16GB Micro SD card
- Sparkfun Pi Servo Shield - DEV-14328
- Pan-tilt kit
- Tower Pro Micro Servo SG90 9 g
I've found that (at least the ones I got) are rather crappy. They are highly non-linear.
- 5 V
- 20 ms (50 Hz) PWM base
- Pulse width encoding:
- 1.0 ms: -90 degrees CCW (left)
- 1.5 ms: 0 degrees (middle)
- 2.0 ms: 90 degrees CW (right)
The linearity of these cheap "Tower Pro" servos is very poor. Going to try "Miuzei" MS-18, with reportedly better linearity and no offest drift.
This is actually designed for LED PWM control, but can be used for servos. It can control 16 output channels. PWM control for each channel is 12-bit (4096 steps).
Drive capability at 5 V:
- 25 mA sink open drain/totem pole
- 10 mA source totem pole
The internal 25 MHz oscillator is not very accurate. That coupled with the granularity of the scaler, pulse widths can not be controlled precisely. With pre scaler register set 121, observed 18.28 ms instead of 20 for 50 Hz.
Power on reset sets output to LOW.
Login via ssh:
ssh pi:[email protected]
Wait about 60 s for the RPI0Z to boot up, when the green LED stops flashing.
In order to use IntelliJ on Mac, set up a share.
In Mac File Sharing > Options, need to:
- allow RPI filder to be shared
- allow user for Windows File Sharing
Tip: copy the following to /home/pi/connect-mac:
sudo mount -t cifs //Franks-MacBook-Pro.local/RPI Projects/RPI -o user=frankw,uid=pi
Determine OS X hostname: hostname -a
Then on Pi, ls ~/Projects/RPI will show empty directories.
Then cd ~/Projects/RPI/pi-rover and the project directory.
These aims diverged a bit and this repo is a bit mixed up.
- Raspberry Pi Zero W V1.1
- Kingston SDC4/16GB Micro SD card
- Sparkfun Pi Servo Shield - DEV-14328
- Pan-tilt kit
- Tower Pro Micro Servo SG90 9 g
I've found that (at least the ones I got) are rather crappy. They are highly non-linear.
- 5 V
- 20 ms (50 Hz) PWM base
- Pulse width encoding:
- 1.0 ms: -90 degrees CCW (left)
- 1.5 ms: 0 degrees (middle)
- 2.0 ms: 90 degrees CW (right)
The linearity of these cheap "Tower Pro" servos is very poor. Going to try "Miuzei" MS-18, with reportedly better linearity and no offest drift.
This is actually designed for LED PWM control, but can be used for servos. It can control 16 output channels. PWM control for each channel is 12-bit (4096 steps).
Drive capability at 5 V:
- 25 mA sink open drain/totem pole
- 10 mA source totem pole
The internal 25 MHz oscillator is not very accurate. That coupled with the granularity of the scaler, pulse widths can not be controlled precisely. With pre scaler register set 121, observed 18.28 ms instead of 20 for 50 Hz.
Power on reset sets output to LOW.
Login via ssh:
ssh pi:[email protected]
Wait about 60 s for the RPI0Z to boot up, when the green LED stops flashing.
In order to use an editor on a host system and run the changes on the RPI, setup up a share as follows.
RULE OF THUMB: Reduce cycle time. In this case, avoid manually copying files from the host to the target.
- select this project's folder in explorer
- right click and choose properties
- select sharing tab
- select your user id
- click share
- select local network Then the folder can be shared as:
/[computer]/rpi-rover
In Mac File Sharing > Options, need to:
- allow RPI filder to be shared
- allow user for Windows File Sharing
Tip: copy the following to /home/pi/connect-mac:
sudo mount -t cifs //computer name/pi-rover Projects/RPI -o user=frankw,uid=bullseye
Determine OS X hostname: hostname -a
Then on Pi, ls ~/Projects/RPI will show empty directories.
Then cd ~/Projects/RPI/pi-rover and the project directory.
Then python src/main/pan-tilt.py
This is the gpio version.
Initial development was with pi-gpio, but latest is using smbus. see src/main/robby/pan-tilt.py
Update on pi:
scp -r ./src [email protected]:/home/pi/Projects/pi-rover
Shell into the pi cd /home/pi/Projects/pi-rover sudo pigpiod python src/main/pi-pigpio.py
To stop: ctrl+c
RPi.GPIO uses software PWM
https://rpitips.com/python-libraries-pigpio/
Well, it's kind of neat to have a full OS, but there are some downsides:
- long boot time (not really long, but too many seconds)
- not a real time OS (maybe there are variants)
- hardware PWM may require low-level language support
I got generic motors, but they look like DAGU
The gear train is a bit noisy.
Initally tried 100 Hz with python pigpio.
| 100 | maybe a bit of dwell at low, can hear the buzz at low values, some glitches | | 1000 | high pitched, doesn't reach full speed | | 500 | like 1000 | | 27 | rough, glitched are more pronounced | | 200 | like 100 |
http://www.techradar.com/how-to/computing/use-a-raspberry-pi-to-remotely-watch-your-home-1314466
v4l2-ctl --list-formats Failed to open /dev/video0: No such file or directory
https://hackernoon.com/spy-your-pet-with-a-raspberry-pi-camera-server-e71bb74f79ea http://192.168.1.1:8081/
uncomment: /tmp/motion.log error opening file /var/lib/motion/01-20180103043953.avi sudo chmod 777 /var/lib/motion works, choppy, dies after a while
take 2 (motion)
sudo modprobe bcm2835-v4l2 sudo service motion start . http://raspberrypi:8081
~1 fps ~2 sec lag
sudo apt install python-smbus
sudo vi /boot/config.txt sudo raspi-config peripherals, enable i2c
http://www.instructables.com/id/How-to-share-files-between-Mac-OSX-and-Raspberry-P/
PWM prescale of 121 results in 54.6 Hz
Got a linux image with BT support baked with the yocto-pi-vm project.
Haven't been able to get hci0 up during startup, so added a script setup-bt.sh to run manually after boot.
The dbus-bt.py script successfully advertises, but not much else yet.
The name is "TESTADVERTISEMENT"
Build the RPI SD card with Yocto project for RPI0W
Not remote: https://projects.raspberrypi.org/en/projects/getting-started-with-picamera
sudo pigpiod
TBD
https://github.com/luetzel/bluez/blob/master/test/example-advertisement
Get bluez version: bluetoothctl --version, currently 5.5.0
Get example code, including python/dbus, from the bluez repo in kernel.org: https://git.kernel.org/pub/scm/bluetooth/bluez.git
Look in the test folder for Python code examples.
https://www.ics.com/blog/control-raspberry-pi-gpio-pins-python