Options; Firmware Upgrades - ozQRP DDS VFO Construction Manual

8 O
PTIONS
LCD
The DDS VFO operates best with a backlit display. The characters are bright and clear and
readable in dim environments. The backlight does consume extra current and if minimizing
current consumption is a priority then a non-backlit LCD can be used instead. In this case
resistor R9 can be left off the board, although leaving it in will not cause any issues.
If an LCD with backlight is used, but is not the same as listed in the parts list, the backlight may
require a different value of current limiting resistor. Check the LCD data sheet before applying
power to determine the correct resistor value and change R9 if needed.
A non-backlit display will also not be as deep and this needs to be taken into account when
mounting to the front panel.
Additional inputs
The PCB includes two additional inputs. One is intended to measure an analog voltage and the
other is configured as a digital input. Both are able to handle a voltage between 0 and 20V DC
maximum. The current firmware release does not utilize these inputs and so when making the 4
pin power cable these pins can be left unterminated.

Firmware upgrades

The PCB contains a functioning 6 pin ISP header to allow future firmware upgrades.
DDS VFO Construction Manual – Issue 1 Page 14