Bryon, Where can we get a copy of tato's bootloader? I have Wouter's
already.

--Bob

Byron A Jeff wrote:

> On Sat, Jun 26, 2004 at 12:49:15PM -0400, Victor Faria wrote:
>
>>Sorry if this is a stupid question??
>
>
> Why would you think that?
>
>
>>But with all the talk about bootloaders is it possible to turn these into a
>>single pin loader???
>
>
> Of course! Tato's loader is a prime candidate because it bit bangs the
> serial interface.
>
>
>>Much like Wouter's. Even if it costs some memory but you gain a pin it may
>>be a good trade off!!
>
>
> There are more advantages:
>
> 1) You get to pick the I/O pin.
> 2) You don't have to tie up the USART.
> 3) Since it's a bit banged interface you can dynamically adjust the bit rate
>    so that the load will work using the internal oscillator even when the temp
>    fluctuates.
>
>
> Wouter's basic idea is sound. A single pin interface is created by tying the
> RX and TX pins of the serial interface via a resistor (he shows 330 ohms
> on his WLoader schematic here: http://www.voti.nl/wloader). Then the TX
> driver output pin is connected directly to a PIC I/O pin. So the PIC I/O pin
> can drive TX, receive from RX, with only the minor side effect of everything
> from RX being echoed to TX, which is actually a good check for the PC side
> loader software.
>
> BTW for bit banging serial Timer 2 is great as a bit rate generator when it's
> available. With the period register PR2 set, the timer will auto reset after
> the given interface. So you can set it to time out and auto reset after one
> bit cell. Then only a single bit needs to be checked to see when to transmit
> or receive the next bit from the serial interface.
>
> Lastly the single pin interface will cost only a trivial amount of code over
> a 2 pin bit banged interface. The only difference is that you have to turn
> the TRIS bit for the pin around from transmitting to received. Otherwise it's
> exactly the same. So 2 instructions to save an I/O pin, especially on an 18
> pin part? Definitely a winner.
>
> BAJ
>
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>


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         Bob Axtell
PIC Hardware & Firmware Dev
   http://beam.to/baxtell
       1-520-219-2363

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