cDMXdriver

Driver to use a serial port on linux to output a dmx-signal

About

Hardware

Use the TX pin of your serial port or usb to serial adapter (e.g. CP2102 or FT232RL) as a input for a RS485 transmitter (e.g.MAX485). Connect the output of the RS485 transmitter to your DMX device.

example for MAX485:

• Pin 3, 8 at Vcc = 5V
• Pin 2, 8 at GND
• Pin 1 over 120Ohm at GND
• Pin 4 TX as input signal
• Pin 6 as DMX HOT (+)
• Pin 7 as DMX COLD (-)

Functions

• struct dmxPort: A struct in which all important data is stored. It is stored in shared memory.
• initDMXPort(port): The function to generate a dmxPort struct (as shared memory). It configures the serial port, initializes the variables and returns a pointer to the generated dmx Port. The parameter specifies the port e.g. "/dev/ttyUSB0".
• setMaxDMXChannel(dmx, maxChannel): Set the highest send DMX channel. You should use this to get a higher output frequency cf. img/.
• setDMXChannel(dmx, channel, value): Set a channel (1-512) to a value (0-255).
• getDMXChannel(dmx, channel): Get a channel (1-512).
• getDMXOutputPointer(dmx): Get a pointer to the output array. Channels from 0 to 511.
• startDMXOutput(dmx): Start sending the dmx signal (makes a fork and call 'dmxThreadFunction').
• stopDMXOutput(dmx): Stops the active output.
• closeDMXPort(dmx): Stops sending signals and closes the serial port.

Notes

• I used a CP2102 USB to TTL adapter with MAX485 to test the software successfully.
• Look in the img folder for oszi images.
• There are some ohter usefull functions. Take a look at cDMXdriver.h.