Dodgy RS232-TTL converters?

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So I got a few of these, mainly to talk to Arduino boards.

As my PC has a real old-style serial port I foolishly though that these  
might be less troublesome than USB-serial converters (think FTDI gate).

To cut a long story as short as possible - I had endless trouble with these.  
One kept latching up and overheating. None of them worked to program an  
Arduino board, and they could not even consistently pass an echo test.

I identified two possible causes. Firstly there is no decoupling of the  
supply on the board, and secondly, left to its own devices, the MAX3232 chip  
has a floating logic level input. Both of these are contrary to  
recommendations in the MAX3232 data sheet I turned up.

I grounded the unused input on one of the boards, and added a decoupling  
capacitor, and while it is still not entirely trouble-free, I did finally  
manage to program an Arduino with it.

I guess a further possibility is that I may have avoided the hazard of  
counterfeit USB chips, only to encounter fake MAX3232s. I note the term  
"domestic MAX3232" on the manufacturer's web site - whatever that means. For  
some other similar boards they mention that the chip is made in China, with  
similar "cautious to buy" warnings.


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