MAX232A with PIC18F452 QwikFlash board.

bonxer · Jan 19, 2005

I am making the QwikFlash board from Peatman's PIC18F452 book. I had some MAX232 chips setting around so I didn't order the more expensive MAX232A. After reading some in the book, I notice it says not to use anything but the A version, due to capacitance. I was wondering, could I just switch out a capacitor and use my other MAX232's? Or do I definitely have to order a $5 A revision? What is the difference that makes them so much more expensive everywhere?

Nigel Goodwin · Jan 19, 2005

bonxer said:
I am making the QwikFlash board from Peatman's PIC18F452 book. I had some MAX232 chips setting around so I didn't order the more expensive MAX232A. After reading some in the book, I notice it says not to use anything but the A version, due to capacitance. I was wondering, could I just switch out a capacitor and use my other MAX232's? Or do I definitely have to order a $5 A revision? What is the difference that makes them so much more expensive everywhere?

My first thought (without checking) is that the A version probably uses much smaller capacitors, as long as you use the correct capacitors for the 'non-A' version it shouldn't make any difference.

The capacitors aren't particularly critical, but some chips use ones MUCH smaller - perhaps that's the difference with an A?.

BTW, what does a QwikFlash board do?, is it a bootloader for the 18F?.

bonxer · Jan 19, 2005

Here's a link to it.
http://www.picbook.com/qwikflash.html

The PCB is included with the 18F452 book.
It's just a small board having everything set up to follow all the examples in the book. It does bootloading, as the PIC has to be initially programmed from another device. It's pretty neat in that if you have multiple QwikFlash boards, you can chain them together with ribbon cables and use them to debug each other. It's got LEDs, switches, an LCD, serial comm, thermister, and rotary knobs. Kind of a fun little toy.

Nigel Goodwin · Jan 19, 2005

bonxer said:
Here's a link to it.
http://www.picbook.com/qwikflash.html

The PCB is included with the 18F452 book.
It's just a small board having everything set up to follow all the examples in the book. It does bootloading, as the PIC has to be initially programmed from another device. It's pretty neat in that if you have multiple QwikFlash boards, you can chain them together with ribbon cables and use them to debug each other. It's got LEDs, switches, an LCD, serial comm, thermister, and rotary knobs. Kind of a fun little toy.

I've check the circuit, it uses 0.1uF capacitors (far too small for a MAX232), assuming the pin connections are the same as a normal MAX232 you could replace them with larger ones - something like 10uF is normal.

If you check the RS232 board in my tutorials, that uses a normal MAX232, and has values that work, and shows which way to connect the capacitors.

Mike - K8LH · Jan 22, 2005

The MAX202CPE and ST202 devices are less expensive, are pin-for-pin compatible with the '232 and '232A, and both can use the 0.1uf monolythic capacitors...

Good luck with your project... Regards, Mike - K8LH

Andy_123 · Jan 22, 2005

You can use MAX232 if all pump 4 capacitors incereased to 1.0uF or higher, just make sure thay all the same.

MAX232A, MAX202 from MAXIM and all other brands of MAX202 replacements use 0.1uF capacitors.

MAX232 of all brands use 1.0uF capacitors.

MAX232A with PIC18F452 QwikFlash board.

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