*** UPDATE *** Realtime UDP control now fully tested and latency between command and control has been completely eliminated. Many UDP controllers can be connected at the same time to get instantaneous updates and control. We are currently using 7 16 channel relay boards in our current setup driving the relays with a 88 key MIDI keyboard, a MIDI controller and a realtime web interface using a combination of udptelnet with websocketd. The startup 50ms latency problem has been resolved, latency is virtually eliminated while using UDP sockets to drive this software.
C program to enumerate and control SainSmart 16 channel relay boards. I created this software for the Reared In Steel Flower Tower Fire Effects for Burning Man. I needed to gang multiple boards and control them as one unit. This software enumerates all SainSmart USB boards and lets you control up to 4 boards with one command.
This software is still in flux and the Daemonize functions are not yet fully tested.
Clone into a directory, enter the source directory and type 'make'. This will generate a binary called 'usb-relay'. You should not need any non standard or special libraries to build this software as it directly uses hidraw. This has been built on raspberry pi's and Ubuntu desktops, but it should build and run on most linux systems.
Currently this software can be driven from the command line in interactive mode or by a UDP socket. I primarily use it via websockets with websocketd controlling it with a web interface
SainSmartUsbRelay Aug 15 2017 at 04:44:18
Version 0.1 - https://github.com/lowerpower/SainSmartUsbRelay
usage: ./usb-relay [-h] [-v(erbose)] [-c udp_command_port] bitmask
-h this output.
-v verbosity.
-t run test.
-c command port (defaults 1026)
-e emulate number of boards (no hardware needed)
When run without options the software will run in interactive mode. It will enumerate all the relay boards and allow them to be set and read. If one board is found the bitmask would be 4 hex digits long, two boards are found the bitmask would be 8 hex digits long and so on.
Interactive commands are in the following format:
[command] <bitmask> <hold time>
Commands that are supported are set, get, quit.
'get' by itself will return the current relay state.
'set' requires a bitmask, and an optional 'hold time' in 100's of MS increments.
Example set relays 16-13 and 5-8
set F0F0[enter]
-returns
F0F0
Example set relay 1 on second board
set 10000[enter]
-returns
10000
Example set relay 1 on first board with 500ms hold time
set 1 5[enter]
-returns
1
When a hold time is specified, the state will be immediately returned, but the next command will not be processed until hold time has expired. This allows control programs using websockets to be totally event driven without having to rely on timer callbacks.
You can run the software without hardware when started in emulation mode. This is enabled by specifying the -e option on the command line with the number of boards you wish to emulate (valid range 1-4). The number of relay boards will be virtually enumerated and allowed to be virtually set and read.
I discovered websocketd and used this instead of a more complex scheme I had initially contrived using UDP sockets and php. Websocketd allows you to 'websocket' enable a stdio program. Since I had built the interactive mode into this software, this mapped nicely to websockets. You can enable this software with the following command:
/path/to/websocketd --port=8080 /path/to/usb-relay
or emulating 3 relay boards
/path/to/websocketd --port=8080 /path/to/usb-relay -e 3
or run in background with logging to /tmp
nohup /path/to/websocketd --port=8080 /path/to/usb-relay > /tmp/websocketd.log 2>&1 &
Search Amazon for "SainSmart 16-CH USB HID Programmable Control Relay Module + Relay". The unit looks like this:
You will also need a 12V power supply (~1A) connected to the blue connector on the main relay board. Do not connect anything to the green connector on the USB HID board.
- https://github.com/lowerpower/fire-controller-web - Web UI that can drive this software.
- https://www.facebook.com/rearedinsteel/ - Reared In Steel facebook.
- https://www.facebook.com/rearedinsteel/videos/713271008877496/ - project in action on flower tower
- Video Demo of this project integrated into a solution.
- websocketd - allows websocket control of a stdio program.
- https://github.com/mvines/relay : I've borrowed the required hardware section of this document from this site. I also used this software here to help me figure out the USB protocol for these relay boards, this is great software but I needed something a bit different and was more comfortable doing this in C. I highly recommend you look at this software to see if it fits your purpose better than the software here, and for general knowledge.