PIC microcontroller VS other implementations - can I avoid using a PIC?

[barthirst]

I've noticed that most of the serial controllers here are implemented using the PIC microcontroller.

questions:

1 - why always use a PIC? Is this for compactness?

2 - Can't I use a UART & Analog to Digital circuit instead?

p.s. the reason i'm shying away from PIC is that I need to program the pic, or buy a programmed one... etc. I would rather build a serial interface from off the shelf (radio-shack) components!

thx,
Bart

[Mike Roberts]

Bart

The simple 2 transistor interface works with Windows 95 to ME but is not compatable with W2000 or XP. This is because it uses the 'ring indicator' pin rather than normal serial transfer. MS have dropped support for this pin in their later systems.
The PIC Serial interface translates the transmitter pulse train into real bytes of serial data transmitted by normal methods. Hence the PIC version is compatable with all systems. I also recon that the PIC version is slightly smoother. The 19,200 baud PIC version is able to send the data for one pulse during the first 1ms of the following one. It can then concentrate 100% on getting an accurate reading the next - and so on.
The IQR serial (and Parallel) interfaces rely on the PC clock for time measurement. If the PC is distracted (higher priority interrupts) it will make a slight error. Nevertheless if you have W95 - ME and a soldering iron I recommend you make up the IRQ version. I have circuit diagrams and transmitter connection details on my website. And if all else fails I'll be happy to supply you a PIC version!

Happy flying

Mike

[Steve Lewin]

As Mike says there are 2 different types of serial interface. If you don't need Win2000/XP support then there is no need for a PIC. A couple of transistors does it fine.

However if you do need that version you will find that PICs are actually used because they are much easier. While a UART will do the output for you the difficult part is decoding the encoder pulse stream into something to drive it. It's not something you would naturally do with an A-D converter because there are no variable analog voltages, it is the timing of each pulse that is significant. It's certainly possible and there are a few different ways it could be done but I doubt if anyone actually has a design for you because a microcontroller implementation is just so much simpler and cheaper.

Steve

[barthirst]

Well I definitely do need support for winXP / 2k. I was thinking about home-brewing a circuit for this, but more and more i'm thinking I should go get a book on microcontrollers and start driving into there. After reading your responses (thanks guys!) microcontrollers are looking better and better! Simple & cheap that's what i'm talking about.

but how much does a PIC programmer cost? Does anyone just sell a programmed PIC I could build around?

[Eric Brouwer]

Have a look on my webpage. There is a section with all the popular Microchip datasheets, Microchip's MP Lab IDE, as well as a cheap and easy programmer you can build yourself with software.

You won't regret the effort. Once into PIC's, you will experience the joy of building complex circuits with only one IC.

[barthirst]

Eric,

I've been eyeing your page all along It looks really cool and I think you're right. I'm gonna go fer it :p (build PIC programmer, get a few PICs and start coding) joy is good!