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USART to RS232

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ChArLyZzZ

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Hello..
I want to connect a DB9 female to MAX232 to interface it with my On chip USART...I checked Nigel's tutorial but i have a question. Can i leave all the pins floating except the GND, TXD, RXD ?? As for the capacitors, the datasheet for the MAX232 specifies 1 uF for all capacitors!!
Thanks
 
Yes you can leave them floating, it's totally safe. There are two revisions of MAX232, the old non-A needs 1uF caps, the new A version is fine with 100nF. So maybe Nigel is using the A version and you checked the datasheet of non-A...
 
To supplement Jay's post... The '232A allows using miniature 0.1uf monolythic caps' which are much smaller than 1uf electrolytics... Although, Randy at Glitchbuster.com sells some super miniature 1uf electrolytics that are about as tall as the 16pin DIP socket...

The MAX202 and ST202 are pin compatible with the '232A and can alsu use the 0.1uf caps...

Good luck with your project... Regards, Mike
 
Yeah I really recommend that 232A. It costs a little bit more but you save on caps.

Once you can use 0.1uF, you can get by with cheap ceramic caps. I use a lot of these listed below for all sorts of decoupling purposes. Many apps don't need that much capacitance but it's way handy to be able to buy only one type of part and the price is still right. Can't ask for a smaller pkg either.

https://www.allelectronics.com/cgi-bin/category.cgi?category=140&item=CM-104B&type=store
 
ChArLyZzZ said:
As for the capacitors, the datasheet for the MAX232 specifies 1 uF for all capacitors!!
Thanks

The capacitor values aren't critical, the values I used were off another datasheet - either those, or 1uF, would be fine.

As suggested, the A version allows the use of far smaller capacitors.
 
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