Ronja Twibright Labs

Duty cycle preemphasis test with Bertest



  • A computer with 1 free full duplex network interface card (NIC)
  • Linux OS where C programs can be compiled
  • Bertest installed
  • Twister or AUI Forte
  • Ronja 10M Metropolis transmitter that is being tested
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Connect the device

Connect the device to the NIC according to the picture. If it's Twister, power it up.

Turning on the interface

If the interface is not up, turn it on (possibly ifconfig eth? up. You don't have to assign an IP address.

Eye test

Note: for Inferno, you have to use B/W CCD camera or night shot camcorder instead of eyes because the light is invisible.

Enter the directory with compiled Bertest and run ./permanent_10 and break it. Repeat couple of times and look at the transmitter during that:

  • If the LED is shining more during ./permanent_10 , then the preemphasis circuit is telling the LED to shine too long (test failed).
  • If the LED is shining less during ./permanent_10, then the LED is shining too short time (test failed).
  • If you cannot tell a difference, then the duty cycle preemphasis is set correctly (test passed).

Multimeter test

If the eye test passed and you have a photocell or large area photodiode, connect that to a multimeter set to suitable current range, and place it it over the TX LED and secure by some heavy enough object. Then repeat the same, but instead of eye use the multimeter. The higher current, the more the LED is shining.

An expected information missing here?