On Wed, 25 Mar 1998 17:38:58 PST Rob Roy writes: >Hi; > > I was wondering if anyone has wrestled with trying to eliminate rs232 >line drivers and their associated capacitors from a dongle like device >attached to a PC or similar serial port I know that I can use a >MAX232A >to convert my 16c5X software UART lines to serial levels and vice >versa, >however I was wondering since resistors and diodes are cheaper and my >supply voltage is +10v & -10v If you have +-10V supplies available, consider using a 1488 or 14C88 quad line driver. These require no external parts and supply 4 fully RS-232 compliant outputs. Most PC's will accept a 0-5V level directly from a PIC output. But some won't, so a driver circuit of some sort is a very good idea. Reception is easily done by just connecting the RS-232 line through a large resistor (100K-1M) to a PIC pin. The PIC's internal protection diodes will clamp the voltage (Don't use the RA4 pin as it has no protection diode to Vdd). A pull-down resistor from the RS-232 input to ground should be installed to ensure a "mark" (idle) reading with the RS-232 input disconnected. >and do something as simple with the output like > > |/---------/\/\/\/\/\/-------<+10v >PIC>-----/\/\/\----------| > |\ > |----------/\/\/\/\/\---------<-10v > | > |-----