Rs232 convertor and avr

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How connect bf-810 usb to serial module to atmega 8a rx and tx pins ? Can I connect rx to tx and tx to rx pins directly or should use max232 between avr and bf-810?

Last Edited: Wed. Jun 29, 2022 - 02:18 PM
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First off.  Please post a link to the specific hardware.  Otherwise we have to Google and guess.

 

e.g. this item https://www.ebay.co.uk/itm/291072536694 requires a MAX232 between the AVR and the DB9 socket.

 

You need a USB to TTL logic level dongle like this https://www.ebay.co.uk/itm/304539864414

 

David.

Last Edited: Wed. Jun 29, 2022 - 02:31 PM
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connect bf-810 usb to serial module

I'd be VERY careful - that looks like a USB-RS232 not USB-TTL so the Tx/Rx pins will likely have -12V/+12V signalling. If you connect that to a 0V..5V AVR bad things may happen.

 

This kind of adapter dates from a previous era when people used printers/modems/etc which really did have +12V/-12V RS232 interfaces. In part they work because after they have done USB to UART conversion they then pass their signals through a MAX232 on board that converts 0/5V into -12V/+12V. To use such an adapter with an AVR you then needed to add a SECOND MAX232 to your AVR circuit that would then bring the signals back down from -12V/+12V to 0/5V .

 

Finally someone spotted that if you made USB converter cables that did not have a MAX232 at all you wouldn't need a second MAX232 in the AVR circuit. So these days most folks choose to use USB-TTL cables like:

 

https://www.ebay.co.uk/itm/13415...

 

That cable has USB on one end that you plug into your PC and Gnd/5V/Tx/Rx at the other end that you plug straight onto an AVR.

 

So you have two choices:

 

1) stick with the adapter you have got and buy a MAX232 (and five capacitors it needs) and wire up a buffer between the adapter you have and the AVR

 

2) for the same money (and a lot less hassle) just buy a USB-TTL cable from your local eBay

Last Edited: Wed. Jun 29, 2022 - 02:41 PM
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Why using bf-810 instead of just simply using USB to TTL UART Serial convertor Module?

 

EDIT :- Too late.

“Everyone knows that debugging is twice as hard as writing a program in the first place. So if you're as clever as you can be when you write it, how will you ever debug it?” - Brian W. Kernighan
“Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.” - Antoine de Saint-Exupery

Last Edited: Wed. Jun 29, 2022 - 02:38 PM
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Thanks a lot for reply.yes