70016 Parallax Inc, 70016 Datasheet - Page 199

• Manufacturer Part Number: 70016
• Description: TEXT INFRARED REMOTE FOR BOE-BOT
• Manufacturer: Parallax Inc

Specifications of 70016

• Accessory Type: Manual
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Boe-Bot®
• For Use With: 29122 - KIT PARTS IR REMOTE FOR BOE-BOT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

Appendix C: Transmitting IR Remote Signals with
the BASIC Stamp 2
The activities in this text focused on programming the BASIC Stamp to receive and
decode IR remote signals. If you are also interested in encoding and transmitting the
same signals an IR remote would send, this appendix/activity provides a circuit and
example programs that can actually be used in place of the universal remote to send
SONY TV control commands to the Boe-Bot.
Pulse Controlled 38 kHz Transmitter Parts
Next to the circuit from the previous appendix, the parts for the circuit in this appendix
are arguably the second least expensive form of wireless communication between BASIC
Stamps. Some of the parts listed here are not included in the Boe-Bot or IR Remote for
Other Protocols
Several IR remote protocols can be transmitted by the BASIC Stamp 2. Typically, if the 38
kHz transmit times and the delays between transmit times are greater than or equal to 0.6
ms, it’s possible to write a PBASIC program to make the BASIC Stamp 2 do the job. The
challenge is typically writing code to control the transmit and delay times. This code has to
be executed during the delays, and it contributes to the delays as well. If the code takes
longer to do the calculations than the protocol allows for the delays, it may be necessary to
use a different microcontroller (see Better Tools and Other Protocols, below).
There is usually more than one way to write code that calculates the 38 kHz transmit times,
and it can make a big difference in the delays between transmits. PULSOUT commands to
unconnected pins can further tune the delay times when they are critical to the protocol.
This kind of tuning involves monitoring the signals the BASIC Stamp sends with an
oscilloscope. (See Understanding Signals, which has a section on analyzing the SONY
protocol with the Parallax USB Oscilloscope. Both Understanding Signals and the Parallax
USB Oscilloscope are available at www.parallax.com)
Better Tools for Other Protocols
Although several different protocols can be mimicked by the BASIC Stamp 2 with the help of
the 555 timer circuit introduced in this activity, it really isn't the best tool for the job. It's kind
of like using a hammer and a nail to make a hole. It would be better to just use a drill.
Microcontrollers like the SX and Propeller are much better suited to precisely timing signals,
and they do not need an external 555 timer circuit. They are also reasonable next steps
after you have become comfortable with BASIC Stamp programs and circuits. Programs for
the Propeller and SX microcontrollers typically monitor an internal timer and turn the 38 kHz
signals on/off at the required time intervals.
For more information about the SX and Propeller microcontrollers, go to www.parallax.com.