Enclosed is a very rough cut & paste spec I have assembled from all the applicable comments. Look this over and e-mail me your comments so I can firm up a real spec. I am really making an attempt to get something usable and worth while for the professional, hobbyist, and student. A lot of these are great suggestions. We need to start putting them in a semi permanent form. Regards, Ed ------------------------------- Original Message ------------------------------------------------------------ I am looking at designing a training / evaluation board for the new 877 series processors. Anyone have any suggestions on what might be included on the board to enhance its' usefulness. I was putting an RS-232 I/F, an LCD display (20 characters by 2 or 4 lines), LDO regulator, Fuse, Expansion connectors, ICD port, and RTC. -------------------------------- Comments to Date -------------------------------------------------------- 1. Put pads and/or holes in the board for the possible use of I2C and/or SPI type components. I would suggest using at least 14 pin devices. 8 pin parts will still fit within the 14 pin area. I would also recommend using only DIP or SM (SOIC) parts. How about provisions for SPI and I2C. Also, maybe provisions for RS485 support/ components. And a breadboard area with pads for DIP and SM components. 2. I would allow at least 2 14 pin pad configurations for the purpose of mounting 1 or 2 OP-AMP packages with up to 4 amplifiers in each package. This should be sufficient for amplifying and or scaling sensor outputs. 3. Another thing I might consider is a place for another 3 pin voltage regulator configured as a constant current source. This might come in handy for supplying certain sensors. 4. A place for an FPGA like I suggested earlier. You would need to make sure that you select an FPGA that allows for the outputs to tri-state based on an input since that is one of the big advantages of having programmatic control of the IO pins or make sure that it can be programmed via I2C so that only 2 PIC pins are used. This brings up a good question. Or actually questions. Such as How many pins? What package? What brand or Mfg? And again maybe the answer is to use a socket or have pads available for it. My personal preference would probably be XILINX. They have a CPLD that is programmable and reprogrammable up to 10K times.The XILINX parts I am speaking of come in 44, 84, 100, 160, 208, and 304 pin versions. I would think that the 100 pin and less parts would be the best here. It just depends on how sophisticated your designs will be. I would go with the 84 pin for a 40 pin processor, and maybe the 44 pin for the 28 pins versions. I'd suggest a row of tiny SMD LEDs along one edge of the PCB to indicate circuit status...voltages ok, heartbeat (osc), chip enable, etc. Sorry, I'm too green to really suggest the proper parameters, just the concept. Forty years of troubleshooting has taught and re-taught me time and again to forget the symptoms and look at the basics first...but I still tend not too. If vss is insufficient for some reason, a red (rather than green) led glowing on the edge may save what few hairs remain on my head. Heartbeat LED not blinking (or too fast/slow)...what happened to my osc? Hm... How about an IR interface.... IRDA?? so those with IR output on their laptops can talk to it, via lightwaves?? * Room around the PIC site to accommodate an Aries ZIF socket, and a parallel port programming circuit, sort of like the Micro Engineering Labs EPIC or the Parallax /TechTools programmer? Perhaps the board could be designed so that it could be used as an extra general-purpose PIC programming board to have around, once one is past the eval stage. * Sockets and/or sites for an external parallel-to-serial and serial-to-parallel latches (both hooked on the serial side to the PIC with 2x8 connection header on the opposite side), I2C EEPROM, LM34/35. * Circuit to convert a thermistor value to an analog input on the PIC, so you can just plug the thermistor into, say, a screw-down header. * Site for a general-purpose instrumentation amplifier (e.g., AD627) and associated gain-setting resistors. Finally, any comments on the following items? 1. CAN interface 2. RS-485 interface 3. The LCD Vs LED display. I am leaning toward a 4 line X 20 character. Low cost chip-on-glass. 4. RS-232 interface (using the A version of the MAX232 because it uses smaller cap (0.1 uF Vs 1.0 uF)) 5. Provisions for an ICD and ICSP (in circuit serial programming) ports for those interested in Microchip support. 6. And, lastly Scenix support, well maybe??