6

My mac is connected to four raspberry pi's using a desktop switch. My mac has ip 192.168.1.90 and my RPi's 192.168.1.11, 192.168.1.12, 192.168.1.13, 192.168.1.14. I can control them via ssh using the terminal on my mac, e.g. ssh [email protected] and can have four terminal screens open to control each one of them.

I would like to sent the same command (to control the camera) to each of the four raspberry pi's at the same time. Instead of copy pasting the command to the four terminal windows, would it be possible to somehow control the four pi's at the same time in one terminal window?

Improve this question
1

4 Answers 4

Reset to default
4

If you're asking about controlling the Pi's camera module specifically (as opposed to something like a USB webcam), you might want to have a look at my compoundpi project which was built for this purpose (it'll handle 4 quite happily; I originally made it for a group at the local university which had 20!).

It includes a console and GUI client which should work on Mac (it's all written in Python; the console client should work "out of the box" on Mac but the GUI client will involve installing the PyQt4 bindings). There's also a Python-based client library for scripting.

At the moment, the client has only been tested on Linux (Ubuntu) and Windows (works, but it's a pain to install). I'd be interested to hear of Mac experiences!

Improve this answer
5
  • Very nice indeed! +beer Commented Nov 7, 2014 at 11:39
  • Just to let you know also when navigation to your org.uk site I can see your cert data. better sort that out quick, revoke and regenerate Commented Nov 7, 2014 at 11:40
  • Wow this looks brilliant and exactly what I was looking for! Thanks for sharing. I will need some more time to try it all out and go through all the documents, but will get back to you next week with an update. It would be great if you could help me further with this. I will use it for research on animal behaviour and could acknowledge you for your contributions if interested. Is there an address I could contact you at? Commented Nov 7, 2014 at 11:40
  • @ppumpkin don't worry about those - that's just a self-signed CA I used to use (a few years ago) for internal signing purposes (and it's only the public cert - doesn't matter if anyone gets that). I really should find some time to build a proper website ... too busy with other projects though! Commented Nov 7, 2014 at 13:33
  • 1
    @JolJols - you can find my e-mail address on my GitHub page; I'm trying to find some time to polish off release 0.4 of compoundpi (to take advantage of recent changes in the picamera library, which I also wrote) but it'll probably be December before I to spend any serious time on it. Feel free to e-mail me with any questions/issues though! Commented Nov 7, 2014 at 13:36
4

There is MQTT, a publish/subscribe messaging system. Under Linux it seems to be supported by the mosquitto package.

apt-cache search mosquitto libmosquitto-dev - MQTT version 3.1 client library, development files libmosquitto1 - MQTT version 3.1 client library libmosquittopp-dev - MQTT version 3.1 client C++ library, development files libmosquittopp1 - MQTT version 3.1 client C++ library mosquitto - MQTT version 3.1/3.1.1 compatible message broker mosquitto-clients - Mosquitto command line MQTT clients mosquitto-dbg - debugging symbols for mosquitto binaries python-mosquitto - MQTT version 3.1 Python client library python3-mosquitto - MQTT version 3.1 Python 3 client library libmosquitto0 - MQTT version 3.1 client library libmosquitto0-dev - MQTT version 3.1 client library, development files libmosquittopp0 - MQTT version 3.1 client C++ library libmosquittopp0-dev - MQTT version 3.1 client C++ library, development files

That would allow you to publish the event (take photo) on one machine and have your Pi's subscribed to that event.

This would be a programming solution. I'm not sure if there is a bash interface to the publish/subscribe methods.

I HAVE NOT used it. I'm aware of it simply because I see it often recommended for this sort of task.

You give no indication of any timing constraints, e.g. how closely the photos must be synchronised in time.

EDITED TO ADD

I have had a quick play with mosquitto

sudo apt-get install python-mosquitto # on server and clients sudo apt-get install mosquitto # only needed on server

I wrote a couple of scripts.

The server tells the clients when to take the photos (now or some time in the future).

The clients wait for the specified time and then take the photo (actually it prints diagnostics).

A webm video here

Server Python script

#!/usr/bin/env python import mosquitto import time mq = mosquitto.Mosquitto() # Connect to mercury mq.connect("mercury") # Take a photo now t = time.time() print("take photo at {}".format(t)) mq.publish("photo/trigger", "{}".format(t)) time.sleep(1) # Take a photo in 10 seconds t = time.time() + 10 print("take photo at {}".format(t)) mq.publish("photo/trigger", "{}".format(t)) time.sleep(11) # Take a photo in 5 seconds t = time.time() + 5 print("take photo at {}".format(t)) mq.publish("photo/trigger", "{}".format(t)) time.sleep(6) # Take a photo now t = time.time() print("take photo at {}".format(t)) mq.publish("photo/trigger", "{}".format(t))

Client Python script

#!/usr/bin/env python import mosquitto import time def on_connect(mosq, obj, msg): print "Connected" def on_message(mosq, obj, msg): msg_time = time.time() snap_time = float(msg.payload) while time.time() < snap_time: pass now_time = time.time() print ("msg={}, snap={}, now={}".format(msg_time, snap_time, now_time)) mq = mosquitto.Mosquitto() #define callbacks mq.on_message = on_message mq.on_connect = on_connect #connect mq.connect("mercury") #subscribe to topic mq.subscribe("photo/trigger") #keep connected to broker while mq.loop() == 0: pass
Improve this answer
4
  • Thanks Joan. That sounds like an interesting idea but the suggestion of Hari to create some kind of shell/bash script sounds easier. Commented Nov 7, 2014 at 8:48
  • @JolJols I have edited my post to add an example script. I thought I might as well try mosquitto. Commented Nov 7, 2014 at 10:59
  • Wow thanks for investing that time. The video and script were very helpful. Could I load the python script on the four raspberry pi's and then run specific python scripts on the server (my mac)? For example, one script would be to record 4 images/sec of a certain resolution for 15min and store them on an usb drive while another would record for 30min at 1fps. Would I be able to run one such script on the terminal, let it terminate, then select another script and run that at a later point in time? Commented Nov 7, 2014 at 11:34
  • 1
    @JolJols Yes, it is flexible enough to handle that. The message names are quite arbitrary as are the strings associated with a message. You could have different scripts on the Pis to process the same message in a different way on each Pi. I've only scratched the surface of MQTT capabilities. If I was going to use it myself I'd probably search for on-line tutorials and spend an hour or so just trying things out in Python or the command line. sudo apt-get install mosquitto-clients will let you send messages from the command line, e.g. mosquitto_pub -t "photo/trigger" -m "23". Commented Nov 7, 2014 at 12:09
2

The simplest way would be to create some kind of a Bash script on your Mac, if you are running bash.

for i in 11 12 13 14; do ssh [email protected].$i "your command here"; done

Maybe some kind of a terminal multiplexer which allows you to send a command to all shells? For instance, on Windows I use Putty, and a tool called "MTPutty" that wraps multiple putty into tabs in the same window, and there's an option to send a script to all Putty sessions simultaneously.

Personally, I would go with the scripting option. Even create a shell script maybe.

Improve this answer
2
  • That is a good idea. I have no experience with bash scripts on mac but will look into it. If I could indeed run a single line like you suggest in one terminal window that could do the trick. If you have any further advice that would be appreciated. Commented Nov 7, 2014 at 8:47
  • Nice one liner :) +beer Commented Nov 7, 2014 at 11:46
2

clusterssh allows you to connect via SSH to multiple servers and send the same commands to each one : clusterssh annotated screenshot

You could also use a terminal emulator that supports groups, such as terminator terminator groups

Improve this answer

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.