Max232A RS-232 Driver/Receiver

Friday, October 14th, 2005

Maxim’s RS-232 level converters are sometimes necessary if a chip or a control board needs to communicate with the PC, especially if the specs for the chip/board indicates that it can only accept TTL/CMOS logic levels. The uControllers, the PIC and the BX-24, that we’ve been using are more tolerant of these voltage levels, so that’s why we can connect the TX/RX of the PC directly to these uControllers.

For situations where you need to shift the voltage levels so you can communicate with a PC(on the PC the voltage swings from +12 to -12 V), you’ll need the Max232A. This bumps up the voltage for serial communication TO the PC(because most chips/boards work on 0 to 5 volts) and lowers the voltage for serial communciations FROM the PC to a safer level for the chips/boards.)

If you are using the MAX232A, you’ll need five 0.1 uF capacitors. The datasheet has a connection diagram that shows 5 polarized capacitors. You can use non-polarized caps. I verified this with MAXIM technical support.

PIC IR remote

Friday, October 14th, 2005

Here’s the info on how to control a SONY TV. (caveat you may need to do some debugging.)

You need a 555 timer to generate the 40 Khz for you.
Your pic just turns on or off the 555 to transmit the appropriate data.

Circuit link.

SIRC codes explained.

SIRC code data format

My PICBasicPro code to implement this protocol.

Update:

Found a simpler solution. Use this IC from rentron. It will generate either a 40 or 38KHz carrier frequency for you. Use the PIC program above and connect the PIC pin to DATA IN of this IC. You need a 4Mhz clock, some pullup/down resistors, and the circuit to drive your IR LED…that’s it!