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 Post subject: USB to Serial cable Noob question please
PostPosted: Thu Feb 13, 2014 6:15 am 
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Joined: Thu Feb 13, 2014 6:07 am
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Hi
I have a USB to serial cable here. It has 5v, gnd, TX and RX. Can I use this to program a nano 8? Looks like I need reset? Can I make something up? Any advice please...
Thanks
John


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 Post subject: Re: USB to Serial cable Noob question please
PostPosted: Thu Feb 13, 2014 10:16 pm 
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Joined: Fri Apr 12, 2013 8:38 pm
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Location: Nottingham, England, UK
HI,

You MAY be able to use your USB serial adaptor BUT its very important that its a USB to TTL Serial converter as if its a true RS232 Serial output it will likely destroy you Nano-8, this is because to program a Nano range micro controller you need TTL signal levels and that's 0V or 5V BUT true RS232 is Plus and Minus 12 Volts so far to high for a Nano without feeding it first through a lever translator like the MAX232 IC,

Assuming your USB converter IS TTL serial output then the next problem is you will need an RTS output to feed the Nano RES pin, this is critical as the Nano communicates with the Basic Micro IDE by resetting the Nano IC and looking for handshake data on the serial lines so with no reset you will get no connection,

If you USB converter is based on the FTDI chip-set then you may be able to take an RTS line from it, its pin 32 of the FTDI IC on the Basic Micro USB programming adaptor BUT if the FTDI IC is surface mount on your adapter cable then getting to this pin without shorting the others out would be very hard to do,

The required programming circuit for the Nano-8 is shown below :-

The Basic Micro Nano USB adaptor is the best way to go as once you have it installed with the supplied drivers they normally work first time, even if you sort the hardware out on yours to gain the RTS line then you may still have driver conflicts leading to slow programming etc so my advice would be to stick to hardware you know and go for the Nano USB adaptor,

I hope this helps,

Dave
BasicMicroUK
http://www.basicmicro.co.uk


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nano8 rs232 program diagram.png
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 Post subject: Re: USB to Serial cable Noob question please
PostPosted: Sun Feb 16, 2014 12:21 pm 
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Joined: Thu Feb 13, 2014 6:07 am
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Thanks indeed for going to the trouble of making such a detailed reply Dave. I understand what is necessary now and think I'll do as you suggested and go for a nano USB adapter.
John


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