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Recent content by kjennejohn

  1. K

    Weird behavior for a xtal osccilator when building USB circuit.

    That sounds like one of the more interesting problems. A crystal that fails to work WITH capacitors? I've designed boards that use PICs, and I've never had problems with the caps or the crystal running. However, here at work, we use 80C51 variations, and the order of the day is to use a one meg...
  2. K

    What are my options - Two uarts needed?

    Since 16Fs and 18Fs are different internally, there will be differences in the C code. As for "best contender", define "best". The 18F45K22 has more of everything, and is only slightly more expensive (Digikey, $3.56, singles). A quick Google on "dual UART microprocessors" shows there are 80C51...
  3. K

    What are my options - Two uarts needed?

    The PICKit2 has a clickable button on its control window that detects the Vcc present on the target board, IF you have Vcc connected to its appropriate pin. Another selection tells it to supply the Vcc to your circuit, but is only good for 100mA max. This is good for the processor and a few...
  4. K

    spi & i2c

    As long as these chips you have are supplied with an enable pin of some kind, there is no reason you can't have them all share the same data pin. But you'll have to come up with other processor pins to exercise these enable pins. Most enables are low-true, meaning that the chip is only usable...
  5. K

    spi & i2c

    As long as these chips you have are supplied with an enable pin of some kind, there is no reason you can't have them all share the same data pin. But you'll have to come up with other processor pins to exercise these enable pins. Most enables are low-true, meaning that the chip is only usable...
  6. K

    What are my options - Two uarts needed?

    The PIC18F25K22 is my idea of a super chip: https://www.electro-tech-online.com/custompdfs/2011/01/41412D.pdf This has two USARTS, is through-holes, has 28 pins, and is really feature packed. I am working with this presently on an early development board and the PICKit2. My compiler is the...
  7. K

    Patent Laws

    I am...happy to say...thoroughly lacking in personal experience in these matters. Which means no one has any reason to sue my ass off and leave me destitute and living in my mother's basement. Which would be a real hardship since she lives in a mobile home. Consider this: Apple sued...
  8. K

    Design review and critique of my first PIC project (serial data tranceiver)

    The ICSP port doesn't match other diagrams I looked up. Olimex ICD2 Programmer Their diagram suggests you got your data and clock pins reversed. Seeing as how this is an Olimex design, an established development board manufacturere and distributor, I tend to believe their diagram. All the...
  9. K

    Motor control project

    Check out this data sheet, especially the schematic at the bottom: https://www.electro-tech-online.com/custompdfs/2010/10/nano_microcontroller_driver_board_B0114.pdf This product uses a 16F88 PIC processor to control either the ULN2803 Darlington array IC, the L293 half-bridge IC, or four...
  10. K

    redesign help diagram plz help

    This circuit is off two ways: - D2 unnecessary. D3 is enough for reverse power input protection. - Need two I/O pins to control T2 and T3, not one pin driving both transistors. You have to be able to turn the segment displays on one at a time, in a multiplex fashion. The first can maybe be...
  11. K

    PIC Communication

    RS485 is probably the best answer. It's quick and simple to implement. You just feed your TTL serial into a MAX485 IC or LTC1481 IC, then through up to a thousand feet of two copper wires to another IC as mentioned at the other end to get TTL out. If you use the direction control pins on the ICs...
  12. K

    Is this PCB fab site OK?

    Right. Dorkbot's three 9.5 sq. in. boards come to $47.5/3, or $15.83 apiece. Actually, five times $15 is $75, not $65, so pcbfabexpress' five 10 sq in boards are $87 for the lot (with $12 shipping) or $92 (with $17 shipping), so $17.4 or $18.40. Not bad for masked and silkscreened boards. I...
  13. K

    Is this PCB fab site OK?

    At ExpressPCB (the fab service I started with) I can get three double-sided boards, 3.8 by 2.5 (28.5 sq. in.) , no mask or silkscreen, shipped next day if ordered M thru F, two day shipping, for $61 (with shipping). Smallest drill size is 13 thou. SMT is a go. This is covered at **broken link...
  14. K

    What is your position in hitech?

    That's what I love about this place. Most people are funny, informed and interesting. I'm your basic electronic bench technician. Have been for 30 years. In all that time I worked on proprietary boards with embedded processors. 6502, 68000, Z80 and 80C51 derivatives. The 68000 was the master...
  15. K

    New to the uC

    If you want to just take it out of the box and start running four servos the same day, get this: **broken link removed** and you'll you'll need the USB programmer, which acts as a serial port after you're done programming: Basic ATOM Nano USB2Serial Adapter It's $25 for the first, $15 for...
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