Dodgy RS232-TTL converters?

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

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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.

Thoughts?

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Andy Wood
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