Assembling the Handy Board, Part 3

Beeper & LCD Circuitry

This is the third step in the Handy Board assembly. In this assembly sequence, the beeper and LCD screen are installed, and Interactive C is brought up on the Handy Board.

For this assembly sequence, collect the following parts:


The LCD screen is presently required for proper functioning of Interactive C. The beeper is not necessary, but provides helpful audio feedback. The resistor pack is used to provide ``hardware defaults'' to some 6811 pins; these are required for the 6811 to operate correctly.

Assembly

Install SPKR1. Orientation is not important.

Get J14, a 14--long strip of female header socket and install in the position of U4. If the female socket header is not precut to the correct length, the socket strip must be cut to size. See the Assembly Tips for instructions on how to do this.

Get J15, a 14--long strip of male pin header and install it in U4, the LCD screen. If the male pin header is not precut to the correct length, simply snap the header to break off a 14--pin segment (a pair of long-nose pliers is helpful when doing this).

Insert the pins from underneath the LCD screen, and solder from the top (see diagram above).

Install RP3* (47K x 9 resistor pack, 10 pins). Make sure to get the pin 1 markings on the resistor packs lined up with the square pads.

Testing

Plug LCD into board and connect the telephone cable from the Interface/Charger board. Make sure the I/C board has power from the wall adapter. Turn on the Handy Board, and observe the LCD screen. The display light dimly, showing a single row of sixteen faint blocks.

Put the Handy Board in bootstrap download mode (hold down the STOP button and turn it on), and run the appropriate version of the 6811 downloading software. If using DLM for MS-DOS or 6811 Downloader for Macintosh, please perform the sequence required to initialize the CONFIG register.

After initializing the CONFIG register, have the downloader load the file pcode_hb.s19. After the downloader finishes, power-cycle the board (make sure the LCD is still plugged in). The board should beep, and the LCD screen should display the Interactive C startup message (e.g., Interactive C V 2.81 9/28/93). If so, congratulations! The Handy Board memory circuit is working properly and communication between the Handy Board and the host computer is functioning.

With the Handy Board still connected and turned on, boot the Interactive C (IC) application on the host computer. IC should communicate with the Handy Board, download some library files, and display the ``C>'' prompt. If this works, take a deep breath and relax! From this point on it's smooth sailing.

Try typing an expression; for example,

1 + 2;
When the return key is pressed, IC will compile this expression, download it to the Handy Board, and cause the Handy Board to execute it. The result is returned to IC; the following should then appear in IC's console window:
Downloading 7 bytes (addresses C200-C206): 7 loaded
Returned 3

Try another:

printf("%f\n", sqrt(10.));
On its LCD screen, the Handy Board should display the result of computing the square root of 10. Note that the Handy Board is performing this calculation, not the host computer.

Debugging

If the LCD screen either does not light at all, or lights strongly, when power is turned on, it may be plugged in backward. Look for a pin 1 marking on the LCD screen; this should plug into the leftmost pin on the Handy Board (labelled GND on the silkscreen legend).

If the download process appears to go correctly, but then the Handy Board does not boot with the Interactive C prompt, the memory circuit may not be working properly. Check the orientations of chips U2 (the memory chip itself), U3 (the 74HC373 chip underneath the memory), and U7 (the 74HC132 chip). If any of the chips is getting hot, it is probably plugged in backward.

Check the soldering joints on the above mentioned chips, re-heating any that appear suspect.

Finally, check continuity for each of the wires in the memory circuit (including address lines, data lines, and select lines). Check that any adjacent wires are not shorted together.


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Fred Martin / MIT Media Laboratory / fredm@media.mit.edu / Thu Jan 2 19:20:33 1997