 |
HC908 VFO
A
DDS VFO using the DDS-30 or DDS60 daughtercard, |
About the
AmQRP Club |
DESCRIPTION
Here's yet another DDS VFO for homebrewers to
try out ... but this one is different from all the rest. It's a derivative
of the Micro908 running on a minimal set of daughtercards: either the DDS-30 or
DDS60, and the powerful HC908 microcontroller daughtercard. This small and
standalone approach gives the builder flexibility in constructing the
application, the advantage of using a ton of tested/proven VFO software, and the
tremendously convenient capability of downloading new software updates from the
website to provide new features as they become available. Other nifty features
such as LCD backlight timeout control, built-in debugger and terminal control,
and programmable scanning capabilities all conspire to make this the most
flexible and singularly-powerful VFO module available on the homebrew market
today.
By the way, this project is not a kit but instead is software that is designed
to run on existing daughtercards that many builders already have, or that can be
obtained as kits/modules from the AmQRP. Using the "reference
design" schematic and parts list, simply wire together the daughtercards
and a few extra components, load up the software from the web page, and you'll
have yourself this great little HC908 VFO.
HC908VFO is a VFO software program that runs on a small, standalone collection of "daughtercards" that will be familiar to Micro908 users. What we did was simply connect the powerful HC908 Daughtercard microcontroller to one of the very popular DDS Daughtercards, and added an LCD and rotary encoder to form a very flexible signal generator in the RF range. We used some of the well-tested software modules from the Micro908 to consruct this simple VFO, then further simplified its operation by giving the user control over a multitude of features.
The single control in the system, the rotary encoder, allows the user to dial in any frequency desired from 1-30 MHz when using the DDS-30 card, or from 1-60 MHz when using the DDS-60 card. One can also set a frequency start, end and step size for a scan through that range. He can also quickly set the frequency dial to any ham band and then conveniently scan just that band. Other menu functions allow for setting timeout on the LCD backlight, selecting which DDS card to enable, allowing control from a PC, and more. Then there's the all-important Software Load function that allows the user to download software updates from the Internet (this website) for the inevitable new features and bug fixes.
Operating the VFO is very straightforward. Turning the dial changes the digit on the frequency dial indicated with the underscore cursor, thus changing the frequency by MHz, 100 kHz, 10 kHz, 1 kHz, 100 Hz, or 10 Hz. Pressing-and-turning the dial positions the cursor to another digit for tuning at at different rate. Pressing-and-releasing the dial brings up the menu, then allowng the user to dial through the menu functions listed int he diagram below. Selecting Exit brings back the frequency dial and the VFO function.
HARDWARE
The schematic shown below is a reference circuit ... an example of how the system components may be wired together. The HC908 VFO is not a hardware kit, but just the software that runs on these readily available components.
PARTS LIST
If you wish to build the HC908 VFO reference circuit, here are the parts needed.
You will also need the daughtercards, of course ... you can find either the kit ordering information or the technical details on them at the links below:
SOFTWARE
The software is the magic of the system and can be downloaded to your PC and easily placed into the flash memory on the HC908 daughtercard without using any expensive hardware. Just follow the easy Loading New Software steps to load the hc908vfo.s19 file into your system and you'll be off and running in no time. The source code is also provided for those wishing to experiment in software.
LOADING NEW SOFTWARE INTO THE HC908 VFO
There are three ways to get software updates into your VFO. Any one can be used, but people have been finding the best luck in the order shown here ...
Method 1) Select "Software Load" in the VFO menu -- With TeraTerm running on your PC, and with the
VFO connected to the serial port of your PC ...
a) select the "Software Load" item in the VFO menu
b) see the HCmon prompt on the PC screen
c) clear the HC908 memory (type 'C' <enter>)
d) load new program (type 'L' <enter> and see 'waiting ...')
e) select TeraTerm's 'Send file ...' item and navigate to the place where the S19 file is that you wish to
load, and then select it
f) see line-after-line of text data being sent to the VFO. When done, the HCmon prompt will be
displayed again;
g) cycle the power on your VFO to restart the program and see the newer version number displayed
on the LCD.Method 2) Select "Debug Monitor" in the VFO Menu -- This method transfers control to the Debug
Monitor that talks to the PC over the serial port. So with TeraTerm or HyperTerminal running
on your PC, you can manually clear memory and load a new program ... just follow steps
b-to-g above.Method 3) Install the P3 MON shunt and enter the low-level Debug Monitor when VFO is turned on.
Follow the same steps (b)-(g) above, and remember to remove the MON jumper before
restarting your VFO.
Material and concepts
presented on the AmQRP website is Copyright 2005 by the American QRP Club,
Inc.
These pages are designed and maintained by George Heron, N2APB
(n2apb_at_amqrp.org)
Page last updated: Feb 6, 2007