BASIC stamp manual v2.2

DTMFOUT – BASIC Stamp Command Reference
Page 180 • BASIC Stamp Syntax and Reference Manual 2.2 • www.parallax.com
The following DTMFOUT instruction will generate DTMF tones on I/O
pin 10:
DTMFOUT 10, [6, 2, 4, 8, 3, 3, 3] ' Call Parallax
If the BASIC Stamp is connected to the phone line properly, the above
command would be equivalent to dialing 624-8333 from a phone keypad.
If you wanted to slow the pace of the dialing to accommodate a noisy
phone line or radio link, you could use the optional OnTime and OffTime
values:
DTMFOUT 10, 500, 100, [ 6, 2, 4, 8, 3, 3, 3] ' Call Parallax, slowly
In this example, on a BS2 the OnTime is set to 500 ms (1/2 second) and
OffTime to 100 ms (1/10th second).
Tone Value Corresponding Telephone Key
0 – 9 Digits 0 through 9
10 Star (*)
11 Pound (#)
12 – 15 Fourth column tones A through D
Table 5.20: DTMF Tones and
Corresponding Telephone Keys.
from I/O pin
1k
0.1
µ F0.01 µ F
1k
Driving an Audio Amplifier
Amplifier
(e
.g., Radio Shack
277-1008C)
Vss Vss Vss
10 µ F (both)
+
+
≥ 40 Ω Speaker
(or 8
Ω in series
with 33
Ω resistor)
from I/O pin
C1 C2
Notes:
C1 may be omitted for piezo speakers
C2 is optional, but reduces high-frequency noise
Driving a Speaker
Vss Vss
Figure 5.4: Example RC Filter
Circuits for Driving an Audio
Amplifier (top) or a Speaker
(bottom).