Category: Hardware

So I’ve got the RPi camera images sending to my laptop now, after installing OpenCV4, and running the test code from https://github.com/jeffbass/imagezmq

Next, we need to try move the servos with code.

https://learn.adafruit.com/16-channel-pwm-servo-driver/python-circuitpython

ok so i installed these

First, if no pip3,
sudo apt-get update
sudo apt-get install python-pip3
Then,

sudo pip3 install adafruit-circuitpython-pca9685
sudo pip3 install adafruit-circuitpython-servokit

Adafruit make you copy paste line by line from here…

https://github.com/adafruit/Adafruit_CircuitPython_Motor

Ok looking in the example folder of that,..

from board import SCL, SDA
import busio
from adafruit_pca9685 import PCA9685
from adafruit_motor import servo
i2c = busio.I2C(SCL, SDA)

pca = PCA9685(i2c)
pca.frequency = 50

servo2 = servo.Servo(pca.channels[2])

for i in range(90):
servo2.angle = i
for i in range(90):
servo2.angle = 90 - i
pca.deinit()

i changed it to 90 degrees and got rid of the comments. It suggests a min and max for the servo.

I ran it and the servo got angry with me and wouldn’t stop. I had to unplug everything because it was eating up the cables in its madness.

Ok so datasheet of MG996R: https://www.electronicoscaldas.com/datasheet/MG996R_Tower-Pro.pdf

It keeps going if I plug just the power back in. It seems to rotate continuously. So something is f***ed. Rebooting RPi. It’s supposed to be 180 degree rotation. Will need to read up on servo GPIO forums.

I also tried the ‘fraction’ style code: https://github.com/adafruit/Adafruit_CircuitPython_Motor/blob/master/examples/motor_pca9685_servo_sweep.py

and it rotated and rotated.

So, I think it must be a continuous servo. Now that I look at the product https://mantech.co.za/ProductInfo.aspx?Item=15M8959 i see it was a continuous servo. Derp.

Ok so let’s see… continuous servo: https://github.com/adafruit/Adafruit_CircuitPython_Motor/blob/master/examples/motor_pca9685_continuous_servo.py

We need to set some limits, apparently these are the defaults.

servo7 = servo.ContinuousServo(pca.channels[7], min_pulse=750, max_pulse=2250)

and possibly set this using a calibrated servo, using the calibrate.py program

pca = PCA9685(i2c, reference_clock_speed=25630710)

https://github.com/adafruit/Adafruit_CircuitPython_PCA9685/tree/master/examples

ok. cool.

At a later date, testing the MG996R servo,

I needed to initialise the min_pulse value at 550, or it continuously rotated.

servo7 = servo.ContinuousServo(pca.channels[1], min_pulse=550, max_pulse=2250)

dev Hardware hardware_ Linux

RPi without keyboard and mouse

Post author By DJ Bro Bot
Post date April 5, 2020

https://sendgrid.com/blog/complete-guide-set-raspberry-pi-without-keyboard-mouse/

https://github.com/motdotla/ansible-pi

First thing is you need a file called ‘ssh’ on the raspbian to enable it:.

https://www.raspberrypi.org/forums/viewtopic.php?t=144839

ok so I found the IP address of the PI

root@chrx:~# nmap -sP 192.168.101.0/24

Starting Nmap 7.60 ( https://nmap.org ) at 2020-04-05 17:06 UTC
Nmap scan report for _gateway (192.168.101.1)
Host is up (0.0026s latency).
MAC Address: B8:69:F4:1B:D5:0F (Unknown)
Nmap scan report for 192.168.101.43
Host is up (0.042s latency).
MAC Address: 28:0D:FC:76:BB:3E (Sony Interactive Entertainment)
Nmap scan report for 192.168.101.100
Host is up (0.049s latency).
MAC Address: 18:F0:E4:E9:AF:E3 (Unknown)
Nmap scan report for 192.168.101.101
Host is up (0.015s latency).
MAC Address: DC:85:DE:22:AC:5D (AzureWave Technology)
Nmap scan report for 192.168.101.103
Host is up (-0.057s latency).
MAC Address: 74:C1:4F:31:47:61 (Unknown)
Nmap scan report for 192.168.101.105
Host is up (-0.097s latency).
MAC Address: B8:27:EB:03:24:B0 (Raspberry Pi Foundation)
Nmap scan report for 192.168.101.111
Host is up (-0.087s latency).
MAC Address: 00:24:D7:87:78:EC (Intel Corporate)
Nmap scan report for 192.168.101.121
Host is up (-0.068s latency).
MAC Address: AC:E0:10:C0:84:26 (Liteon Technology)
Nmap scan report for 192.168.101.130
Host is up (-0.097s latency).
MAC Address: 80:5E:C0:52:7A:27 (Yealink(xiamen) Network Technology)
Nmap scan report for 192.168.101.247
Host is up (0.15s latency).
MAC Address: DC:4F:22:FB:0B:27 (Unknown)
Nmap scan report for chrx (192.168.101.127)
Host is up.
Nmap done: 256 IP addresses (11 hosts up) scanned in 2.45 seconds

if nmap is not installed,

apt-get install nmap

Connect to whatever IP it is

ssh -vvvv pi@192.168.101.105

Are you sure you want to continue connecting (yes/no)? yes

Cool, and to set up wifi, let’s check out this ansible script https://github.com/motdotla/ansible-pi

$ sudo apt update
$ sudo apt install software-properties-common
$ sudo apt-add-repository --yes --update ppa:ansible/ansible
$ sudo apt install ansible

ok 58MB install…

# ansible-playbook playbook.yml -i hosts –ask-pass –become -c paramiko

PLAY [Ansible Playbook for configuring brand new Raspberry Pi]

TASK [Gathering Facts]

TASK [pi : set_fact]
ok: [192.168.101.105]

TASK [pi : Configure WIFI] **
changed: [192.168.101.105]

TASK [pi : Update APT package cache]
[WARNING]: Updating cache and auto-installing missing dependency: python-apt
ok: [192.168.101.105]

TASK [pi : Upgrade APT to the lastest packages] *
changed: [192.168.101.105]

TASK [pi : Reboot] **
changed: [192.168.101.105]

TASK [pi : Wait for Raspberry PI to come back] **
ok: [192.168.101.105 -> localhost]

PLAY RECAP ****
192.168.101.105 : ok=7 changed=3 unreachable=0 failed=0 skipped=0 rescued=0 ignored=0

And I’ll unplug the ethernet and try connect by ssh again

Ah, but it’s moved up to 192.168.1.106 now

nmap -sP 192.168.101.0/24 (I checked again) and now it was ‘Unknown’, but ssh pi@192.168.101.106 worked

(If you can connect to your router, eg. 192.168.0.1 for most D-Link routers, you can go to something like Status -> Wireless, to see connected devices too, and skip the nmap stuff.)

I log in, then to configure some stuff:

sudo raspi-config

Under the interfaces peripheral section, Enable the camera and I2C

sudo apt-get install python-smbus
sudo apt-get install i2c-tools

ok tested with

raspistill -o out.jpg

Then copied across from my computer with

scp pi@192.168.101.106:/home/pi/out.jpg out.jpg

and then make it smaller (because trying to upload the 4MB version no)

convert out.jpg -resize 800×600 new.jpg

Cool and it looks like we also need to expand the partition

sudo raspi-config again, (Advanced Options, and first option)

Upon configuring the latest pi, I needed to first use the ethernet cable,

and then once logged in, use

sudo rfkill unblock 0

to turn on the wifi. The SSID and wifi password could be configured in raspi-config.

At Bitwäsherei, the ethernet cable to the router trick didn’t work.

Instead, as per the resident Gandalf’s advice, the instructions here

https://raspberrypi.stackexchange.com/questions/10251/prepare-sd-card-for-wifi-on-headless-pi

worked for setting up wireless access on the sd card.

“Since May 2016, Raspbian has been able to copy wifi details from /boot/wpa_supplicant.conf into /etc/wpa_supplicant/wpa_supplicant.conf to automatically configure wireless network access”

The file contains

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=«your_ISO-3166-1_two-letter_country_code»

network={
    ssid="«your_SSID»"
    psk="«your_PSK»"
    key_mgmt=WPA-PSK
}

Save, and put sd card in RPi. Wireless working and can ssh in again!

2022 News flash:

Incredibly, some more issues.

New issue, user guide not updated yet

https://stackoverflow.com/questions/71804429/raspberry-pi-ssh-access-denied

In essence, the default pi user no longer exists, so you have to create it and set its password using either the official Imager tool or by creating a userconf file in the boot partition of your microSD card, which should contain a single line of text: username:hashed-password

Default pi and raspberry:

pi:$6$/4.VdYgDm7RJ0qM1$FwXCeQgDKkqrOU3RIRuDSKpauAbBvP11msq9X58c8Que2l1Dwq3vdJMgiZlQSbEXGaY5esVHGBNbCxKLVNqZW1

Hardware hardware_ robots

Robot prep: PWM control

Post author By DJ Bro Bot
Post date April 1, 2020

I started up a raspberry pi with raspbian installed on it. (I used balena’s etcher to flash an sd card): the light version, basically just Debian OS for rpi: https://www.raspberrypi.org/downloads/raspbian/

https://www.balena.io/etcher/

The RPi needs a proper keyboard, at least until you set up ssh and can access it remotely. (

We’re interested in making a robot, and we’re using a Raspberry pi. So we need to control servos. RPi only has a single PWM pin, so we need to use an I2C module https://learn.adafruit.com/16-channel-pwm-servo-driver to control however many servos our robot needs, and the software libs to run it https://github.com/adafruit/Adafruit_Python_PCA9685

and we need an external 5V PSU, to power the servos.

Configuring Your Pi for I2C:

sudo apt-get install python-smbus
sudo apt-get install i2c-tools

Need to connect the RPi to the servo driver. This was a picture taken when testing it on the RPi Zero W in 2019. The instructions for pinout connections: https://learn.adafruit.com/16-channel-pwm-servo-driver/pinouts

Or from Adafruit, for RPi:

(or Arduino)

Ok but how do we power servos? We can’t run it off the RPi’s 5V 2A. Oh duh, there’s that big DC socket connected to the PCA9685

There is something to be said for running the robot on an Arduino. You get something robotic. You upload someone’s hexapod spider code, and it does a little dance. You can control it remotely. It can interact with sensors.

Arduinos are dirt cheap. So I bet we could have tiny neural networks running in arduinos… shit, do we already have them? Let’s see… ok wow there is like a whole thing. https://blog.arduino.cc/2019/10/15/get-started-with-machine-learning-on-arduino/ ok but 2K of RAM is not much. You would need to be a real demo scene junky to use a 2KB NN, but yeah, you could do something crudely intelligent with it.

Robots on ESP32s are definitely a thing. But ok no, Raspberry Pi for real robot. We need Linux for this.

Ok so I need to wire this up. But I also need a chassis for the robot.