HC908 Daughtercard

The controller for the Micro908, the HC908 Commander, and more!

                                                  

   
(Click photos to view full-size image)

DESCRIPTION  |   SCHEMATIC  |  QUICK SPECS  |  MANUAL

PRICE  |  ORDERING  |  AVAILABILITY

RESOURCE PAGE     Check out the HC908VFO Project!

DESCRIPTION
The HC908 Daughtercard  is a self-contained microcontroller on a 2" x 2" pc board that may be used as a standalone computing "block", or as the heart of other projects like the Micro908, or other custom projects for which you might need some computing power.  The HC908 offers lots more computing power and I/O capabilities as compared to a PIC, and the HC908's simple, self-programming feature makes it easily reprogrammable without the need for a special hardware programmer 

The Daughtercard contains components required for clock generation, a MAX-232 chip for serial communications, a voltage regulator and a RESET pushbutton. All I/O pins of the HC908 are brought out to 0.1"-spaced dual-row pin header socket connectors that permit the HC908 Daughtercard to be plugged into mating pin headers on a prototype base board containing other components.

The 64-pin PQFP device is soldered in the center of the card’s top side and its many I/O pins are connected by top-side traces to two 34-position sockets located on either side of the card. These long sockets can plug into mating pin headers located on another board containing additional I/O components, if desired..

The small pushbutton is located on the top side of the daughtercard. This normally-open momentary contact switch serves as a manual RESET for the system.

A 2-position pin header and LED are mounted in the lower corner of the card’s top side, serving to configure and indicate the boot loader feature. (More on this feature in the next section.)

The bottom side of the Daughtercard contains the surface mount components required for clock generation on the microcontroller – a crystal, two capacitors and a resistor. Also located on the bottom side are the LM78L05 3-terminal voltage regulator and associated filter caps, and the components used for serial interface – the MAX-232 level translator for the RS-232 communications port and the five electrolytic capacitors used for charge pump operation.

Creating a universal computing block in the form of a Daughtercard proved to be a very enabling decision. One is able to easily use the Daughtercard for many different applications and project. There is lots of capability in this little 2”-square standalone card – just supply 9-12Vdc and a serial communication line from your PC and you’ll be able to download and burn new programs into your HC908 microcontroller.

Getting Software into the HC908
One of the prime goals for this project was to have the Daughtercard be easily and inexpensively reprogrammable over long-term use in many different applications. Of course the unit has ample onboard flash memory, simplifying the board design and making for a non-volatile project.  That is, the HC908 microcontroller retains its program memory even when power is removed.

But getting the software program into the device is sometimes a concern for microcontroller homebrew enthusiasts due to the expense of the "programmer". Oftentimes it's necessary to purchase a $100-or-more programming board from the manufacturer that will allow you to burn your custom software into the controller's flash memory.  In many cases one is able to homebrew this programmer (as in the case of the PIC devices), however this is yet another project that must be done before getting to the fun part of experimenting with your intended project.

However the good news is that this 68HC908AB32 device has the ability to be in-circuit programmed, which means that a conventional RS232 serial port from a PC is all that's required in order to burn a new program into the HC908's  flash memory ... even when the Daughtercard is on the target board of your project! 

We've developed a special boot loader program that allows you to download the binary image of your program over the built-in RS232 serial data port connected to your PC. All you need to do is develop a program with the free software development tools on your PC, download it to the Daughtercard and bingo, you'll be running your new and improved program.  In this way you'll be able to take advantage of newer software programs that we'll be providing for download on this website, or you can develop your own customized versions of the programs.  Pretty cool, eh?

When it is time for you to get a new software program into your HC908, connect your PC’s serial port to the Daughtercard, install the Monitor Jumper and press the onboard pushbutton to reset the processor. The Daughtercard’s LED will illuminate, indicating that the boot loader software is running. You’ll next transfer the binary file of your new software from your PC using a communications program like HyperTerminal (standard in the Windows Accessory folder). Once the software is downloaded to the HC908 controller, the boot loader proceeds to burn the software into the controller’s flash memory. When successfully completed, control is returned to the HCmon program and the new program may be run. Detailed instructions for this boot load operation are supplied in the HC908 Daughtercard reference manual.)

"Quick Specs"

What comes with the HC908 Daughtercard?

The user experience should be quite fruitful upon first opening the box.  The following items are included ...

Given that the daughtercard comes fully assembled, programmed and tested, all one needs to do is apply power and provide some simple I/O.  The Reference manual describes the different kind of initial experiments you will be able to do with the board, given either controlled by an RS-232 serial port from your computer, or by an inexpensive LCD and pushbutton optionally plugged into the Daughtercard. 

The software "monitor" program (called "HCmon") we designed for the microcontroller gives you the ability to input from various ports and display to the LCD or serial terminal.  HCmon also provides the ability to output digital data to its output ports, with the assumption that the user has wired up some peripherals or other I/O devices to the edge connector of the HC908 Daughtercard.

As you know, the HC908 Daughtercard is designed to serve as the heart of many different microcontroller projects we might soon want to have in our radio shacks.  The most important of which is the Digital QRP Breadboard (DigBB), as chronicled in the pages of QRP Quarterly.  As such, therefore, the HC908 Daughtercard's HCmon monitor software comes programmed with various subroutines in its library that allow for reading a shaft encoder, setting a DDS frequency (and thus serving as a VFO), reading analog voltages and most specifically reading/interpreting signals coming from a reflectometer (SWR bridge), serving as a frequency counter by reading frequency, and many other functions as documented in the DigBB project. 

All software source code listings in the Reference Manual (software source code is also downloadable from the HC908 website) provide a good example of how the various subroutines in the software library may be used to construct your own application.  If you didn't wish to construct the DigBB project, you could of course wire up your own specific hardware project and "re-order" the software routines in the HC908 subroutine library to perform your own control logic.  Thus, you would be able to control a small robot mechanism, control your HF rig by issuing CT commands over the serial line, design a repeater controller, or whatever other end-goal you might have for your HC908 Card.

All software source code listings in the Reference Manual (software source code is also downloadable from the HC908 website) provide a good example of how the various subroutines in the software library may be used to construct your own application.  If you didn't wish to construct the DigBB project, you could of course wire up your own specific hardware project and "re-order" the software routines in the HC908 subroutine library to perform your own control logic.  Thus, you would be able to control a small robot mechanism, control your HF rig by issuing CT commands over the serial line, design a repeater controller, or whatever other end-goal you might have for your HC908 Card.

The free development program from P&E Micro gives you an editor/assembler/debugger for source code programs, then you can download that to the HC908 Daughtercard via your computer's serial port using the built-in boot loader program I designed for the daughtercard. 

Ordering by PayPal

            HC908 Daughtercard: ...... $30      ( Shipping added at checkout.  Tax automatically added for MD residents.)

Ordering by Mail
See price above and add shipping fee ($10 for US and Canada, or $17 for International orders).
Write a check or M.O. for made payable to "Midnight Design Solutions, LLC" and send to:


CURRENT STATUS
We have lots of stock!  

A comprehensive Reference Information is available online at the Resource Page ... 
- Quick Start
- Features & Capabilities
- 'Exerciser' -- a pre-loaded application
- 'HCmon' Command Reference Guide
- 'Hello DDS' -- A Guide to Writing Your First Application
- Schematics, Photos and Diagrams.

The development of this HC908 project was chronicled in my QRP Quarterly columns during 2001-2003, and is currently serving as the heart of the Micro908 (http://www.amqrp.org/kits/micro908).   

Upon opening the HC908 package, all you'll need to do is apply power to the appropriate pins, connect the daughtercard to the serial port of your PC, load up your favorite terminal program on your PC (or use one of the free programs linked on our HC908 web pages), and you'll be using your HC908 as advertised.

The first program to come up (i.e., when the Monitor Jumper is in place on the connector) is the 'HCmonitor' program.  HCmon is a debug monitor which allows you to set breakpoints in the main programs you download from the Internet, inspect and edit memory and registers, and single step from instruction to instruction. HCmon also allows you to erase the flash (nonvolatile) memory on the daughtercard and burn a new software into the  application space of the controller.  This means that when it comes time to  load up the Digital Breadboard software, or the Antenna Analyzer software, or the Commander software, or the VFO software, or any of the other programs available for this project, all you need to is issue the appropriate commands on your terminal program and "voila!", you'll have a new project.

The other program that comes preloaded on the HC908 Daughtercard is called 'Exerciser'.  This is a useful program that exercises (demonstrates, uses, etc.) many of standard components that you'll be putting into the QRP projects you'll be making with this project -- components like shaft encoders, LCD displays, potentiometers, DDS frequency synthesizers, piezo beepers, Morse paddles, switches, LEDs, and more.  Using the Exerciser program as a template or a starting point, you'll be able to easily add your own functionality to customize the project and make it truly your own creation.

By the way, it's important to note that you do not *have* to design a new software program to make use of the HC908.  You can merely download the programs already available for it, wire up some of the peripheral components mentioned above, and you'll have a working VFO, or a working antenna analyzer, and so on.

It is important however to note that this is a "homebrewer's project", meaning that there is still some gathering of parts and assembly required. While we provide some good examples, schematics, part sources, test routines, etc. to help you get your project going, the HC908 daughtercard won't do too much all by itself.  But this pre-assembled/tested computing module will indeed plug into a number of full-fledged and typical project kits we have in the making.   So if you have purchased the HC908 daughtercard, you can experiment with it and build your own project around it, but when some other kits become available later this year, you can merely plug your HC908 into the kit, load up the new software and within minutes have an operational project.

If you are already an HC908 Daughtercard owner, you'll find special value at the Resource Page containing lots of detail, tools and links that will assist you in the initial usage of this product.  

73, George N2APB 

 

Page last updated:  Dec 4, 2013