keypad
The image below is an extract from the schematic for the keypad referred to on page 620 of LAoE.
What does the symbol connecting switch S4 to pin 11 of U7 and connecting pins 6 and 11 of U7 mean in terms of how to wire it up? Does this just indicate direct connections between S4 and pin 11 and between pin 6 and pin 11, with the three unfilled circles and the solid and dotted curved lines indicating the function of S4 as toggling between 10Hz and 20Hz?
Using the following keywords in a search engine> 4x4 keyboard 10 pin One quickly finds several solutions.
Confirm that it matches your pinout using an ohm-meter or by following traces.
Located here with software http://www.mikroe.com/eng/downloads/get/1215/keypad_manual_v100.pdf
Number 1 can be destructive for your controller. If you would use push-pull outputs for the columns, and the rows as inputs, then pressing two keys on the same row will short circuit the power supply through the microcontroller's outputs. If the microcontroller's outputs can be configured as open-drain, then there's no problem, but the outputs must have pull-up resistors as well. Then you basically have number 2, but with the pull-ups integrated.
Number 2. Same story if you would use the rows as outputs. Using the columns as outputs makes more sense, since R1-R3 avoid a short-circuit of the outputs. Note that a low output level will see the series/pull-up resistor as a voltage divider, so that the input will be 0.1 Vcc, though that's usually not a problem.
Number 3 avoids the divider, but the resistors on the inputs don't serve any function. A variant without the series resistor will do.
So 1) may be an absolute no-no. 3) is a bit better than 2) because it doesn't have the voltage divider, but can do without the series resistor.
Best Answer
That'll be a 3-pin header with a jumper to connect the middle pin to either side. It's, effectively a single-pole, double-throw switch.
In your example the wire from the right will connect to the centre pin and the outer pins will connect to FAST (6) and SLOW (11).