Tiny Bootloader 18F2420

[ScaleRobotics]

You can also modify the TinyB18F.asm code for other PIC types. The cool part of using PIC18 device is that you can run the bootloader WITHOUT a MAX232! Just invert your USART with RXDTP and TXCKP. I have been meaning to try it since I read this thread: http://www.picbasic.co.uk/forum/showthread.php?t=10361

I finally tried it using a PIC18f2520 with a 22k resistor on the RX line, and with the addition of

	BSF BAUDCON,RXDTP
	BSF BAUDCON,TXCKP

to the sample .asm file they call TinyB18F.asm , which is included in the Tiny Bootloader download.

Nice to get rid of a $4.00 chip, and do it in hardware, well ... sort of software/hardware!

And it works!!

[rinthesun]

I have tiny working with the 18F252 and the 18F2420. I will upload the file in a day or so.

[Dave]

scalerobotics, WOW you pay $4.00 for an MAX-232.... You must be made of money...

Dave Purola,
N8NTA

[ScaleRobotics]

scalerobotics, WOW you pay $4.00 for an MAX-232.... You must be made of money...

No, mostly water really.

Thanks Dave, I guess I was using a Mercedes, when I could have used a Chevy.

A quick search of Digikey for MAX232 reveals the actual price of a Maxim MAX232 dip is $3.31 to $6.60 ( Unless you like the larger electrolytic caps). But, if you use an ST232C, instead of a MAX232, (after tax and a few capacitors), the cost is $1.25.

Either way, you will save some money and space on your board if you invert your coms and buy two resistors.

[Dave]

scalerobotics, There is just something wrong in my mind about connecting negative voltages to a unipolar input pin... I think the cost of a few transistors and a few resistors is worth the piece of mind....

Dave Purola,
N8NTA