lab-nanny

System to monitor signals from different labs and shares/acts on them remotely—just like a nanny.

The system consists on one or more arduinos, each of them connected via USB to a PC (it could be a Raspberry PI), which are later connected to the network. Each of these (arduino+PC) nodes are then connected to a central server which different clients/users can connect to.

Nodes

Each of the nodes consists of a bunch of sensors connected to the arduino, plus a slave computer which communicates with both the arduino and the master server.

Since the slave nodes are directly connected to the arduinos, they show a much lower latency to their stimuli; one may use this to implement low-latency responses to contingencies. For example, if a TTL pulse signals that a potentially harmful condition is met, one might stop an experiment.

arduino

The arduinos have both input and output ports, with which we can sense and act on the experiment respectively.

They communicate with the PCs connected to them via the serial connection. The node starts the communication with a handshake that arduino must send back to check that the connection works. The handshake, a single char, can either mean to just “send the sensor data” (if char value is 14) or to “perform an action and then send the sensor data” (if char values between 15 and 114). The value of this handshake just turns ON/OFF a particular digital port: chars in the region 65-114 correspond to turning ON channels 0-49, and chars with values 64-15 correspond to their respective OFF values (char 64 corresponds to channel 0 OFF, and char 15 corresponds to channel 49 OFF).

Slave node (servers.server_node)

The slave node is charge of interfacing the arduino and the master server. It can asking arduino for data and change its digital channels (using the above mentioned handshake). It offers the possibility of both I/O to arduino from server requests.

Master server (servers.server_master)

Periodically obtains data from all of the nodes. At the same time, the server currently implements a very rudimentary feedback system controlled by one or more "conditions". These are stored in the servers.server_master._conditions property, and checked with the same period as the nodes data is obtained.

The server stores some data to a sqlite database: it periodically stores a snapshot of the data (with smaller frequency than it obtains data from the nodes) and metadata corresponding to new connections, re-connections and closing connections.

Through the 'SOCKETPORT/status' link, the master server also makes available a summary if its state.

Clients

Coded in HTML + JS. Connect to the master-server, which then sends the data to all connected clients every time the slave nodes sends data back.

How to run

For testing purposes, one can run a master server and a slave node in the same machine. In the lab-nanny folder, execute

python -m servers.server_master

And execute a slave node:

python -m servers.server_node --emulate 1 -r lab6

One can then see the results through the navigator. First, open a server in the lab-nanny folder using

python -m SimpleHTTPServer 3000

which will start serving in http://localhost:3000. Then, go to the "clients" folder, and use the "datavis-master.html".