Hardware Reference
In-Depth Information
▪ 22 kΩ resistor (see
“Resistors”
)
A variable resistor with three terminals
Figure 2-8
shows a simple variable resistor (trimpot) wired to the Bone. One end terminal
is wired to the ADC 1.8 V power supply on pin
P9_32
, and the other end terminal is at-
tached to the ADC ground (
P9_34
). The middle terminal is wired to one of the seven
analog-in ports (
P9_36
).
Figure 2-8. Wiring a 10kΩ variable resistor (trimpot) to an ADC port
Example 2-5
shows the BoneScript code used to read the variable resistor. Add the code
to a file called
analogIn.js
and run it; then change the resistor and run it again. The
voltage read will change.
Example 2-5. Reading an analog voltage (analogIn.js)
#!/usr/bin/env node
var
b
=
require
(
'bonescript'
);
b
.
analogRead
(
'P9_36'
,
printStatus
);
function
printStatus
(
x
) {
console
.
log
(
'x.value = '
+
x
.
value
.
toFixed
(
3
));
console
.
log
(
'x.err = '
+
x
.
err
);
}
