Assembling the Handy Board, Part 5

Analog Input, Infrared, and Expansion Header Circuitry

This is the fifth step in the Handy Board assembly. In this sequence, the analog input connectors, infrared input and output circuitry, and expansion connectors are installed.

For this assembly sequence, collect the following parts:

Resistors:
R3 and R7 (10K--brown, black, orange)
R4 (3.83K precision resistor--orange, grey, orange, brown)
R5 (1K--brown, black, red)
R6 (47K--yellow, purple, orange)
VR1 (20K trimmer potentiometer knob)
Capacitors:
C6 (0.0068 µF, labelled ``682'')
LEDs:
LED9R (HLMP-1700, red)
Integrated Circuits:
U15 (Sharp IS1U60 infrared demodulator)
Connectors and Sockets:
J1 (3 pcs. of 7--pin female socket strip)
J3 (10--pin female socket strip)
J6 (2 pcs. of 4--pin female socket strip)
J8 and J13 (4--pin female socket strip)
J7 (3--pin female socket strip)
Other Components:
Q1 (Zetex ZTX614 NPN Darlington transistor)
SW2 (pushbutton switch)

Analog Inputs

The Handy Board analog input bank connects directly to the 6811's analog inputs. RP3, which has already been installed, is used to provide a default value to these inputs.

Assembly

Get three strips of 7--long female header socket and install in the J1 position. 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.

Install VR1 (20K trimmer potentiometer).

Testing

Boot the Handy Board and Interactive C; load the hbtest.c file. Type ``testanalogs();'' at the IC prompt.

The Handy Board will display the message ``Press START to test knob...'' on its LCD screen. Press the START button, and the screen will show the message ``Turn knob; STOP to end -> xxx,'' where xxx is the current value of the knob. Turn the knob and the value should vary with a minimum of zero and a maximum of 255.

Press the STOP button, and the Handy Board will show the message ``Press START to test analog ins.'' Press the button, and the display will then show a series of seven numbers. They should all be in the range of 250 to 255.

To test the inputs, get a 10K resistor and bend its leads into the shape of a ``U.'' For each sensor column, insert the resistor end in the outermost two connector sockets.

The first number on the display is the value of analog input 6. Insert the resistor into this position; the value being displayed should change to around 45. Check each of the seven analog inputs in this fashion.

Debugging

If particular analog inputs are not working, trace their wiring continuity back to the 6811. Perhaps the 6811 socket leaves are not pressing firmly against the 6811 itself.

If none of the analog inputs works, including the knob, verify that pin 52 of the 6811 is +5v, and pin 51 of the 6811 is ground. These are the voltage reference high and voltage reference low for the 6811 analog input circuit, respectively.

Infrared Input and Output

The Handy Board includes the Sharp IS1U60 infrared demodulator, a device that is used to decode common household TV and VCR infrared transmissions. It also has an oscillator and power output stage for driving infrared LEDs to generate such signals.

Assembly

Output Stage

Install R4, R7, C6, R3, R5, Q1*, and LED9R*.

Get the 3--long piece of female header socket and install in the J7 position. If the female header is not precut, see instructions in the Assembly Tips.

Input Stage

Install R6 and U15*.

Testing

Output Stage

Boot the Handy Board and Interactive C. At the IC prompt, type

poke(0x1000, 0x40);

This turns on the 6811 pin that controls the infrared output oscillator. LED9R should light up. Using an oscilloscope, measure the signal at pin 2 of U9 (the 74HC04). It should be a square wave with a frequency of about 40 kHz (between 39,000 Hz and 41,000 Hz). From IC, issue the command

poke(0x1000, 0);

LED9R should turn off, and the square wave should disappear.

Input Stage

Boot the Handy Board and Interactive C At the IC prompt, type:

while (1) {if (4 & peek(0x1000)) fd(0); else bk(0);}

This statement causes the infrared input signal control the Motor 0 port.

Get a household VCR or TV remote, aim it at the green IS1U60 infrared demodulator, and press a button. Motor 0 should flash green and red while transmitting IR data to the Handy Board, and should light steady green otherwise.

Debugging

Output Stage

If LED9R fails to light after the poke command is issued, trace the following progression of signals. Please refer to the infrared output schematic:

6811 Timer Output 2. This is the signal from the 6811 that enables the IR transmission circuit. Check pin 28 of the 6811; it should be high. The signal is wired to pin 2 of U7; it also should be high.
Oscillator Output. Look at the signal on pin 3U7; when the 6811 timer output 2 is high, it should be a 40 kHz square wave. If not, check for proper installation of U7, R4, and C6.
Inverter. The 40 kHz square wave should go to pin 1 of U9, where it is inverted and output on pin 2 of the same chip.
Transistor Drive. The 40 kHz signal then passes through R3, where it is delivered to the base of Q1. Check for the signal's presence at these points.
Transistor and LED Wiring. Check that the emitter lead of the transistor is properly grounded, and that LED9R and R5 have good solder joints.

Input Stage

Check power and ground on the IS1U60: the center pin is ground; the right-most pin (nearest to the corner of the board) is +5v.

View the output line (the left-most pin) with a logic probe, and aim a TV/VCR remote at the device. Press buttons on the remote, and the output line should strobe low.

A very few TV/VCR remotes will not be compatible with the sensor; if you are stuck try a different remote.

Expansion Connectors

The Handy Board presents a variety of signals available for use by expansion boards, including: the full 6811 data bus (on the LCD connector), select lines for controlling input and output latches, four 6811 analog inputs, the 6811 high speed synchronous communications port (SCI), and motor power and ground.

In this assembly step, the female socket headers for these signals are installed.

Assembly

Get four pieces of 4--long female header socket and install in the J13, J8, and J6 positions.

Get the piece of 10--long female header socket and install in the J3 position.

If the female header is not precut, see instructions in the Assembly Tips.

Testing and Debugging

There are no testing or debugging procedures for this assembly step.

Fred Martin / MIT Media Laboratory / fredm@media.mit.edu / Fri Dec 26 10:21:40 1997