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Author Topic: External power supply with FT232 standalone programmer  (Read 406 times)
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Hello,

At the moment I'm building a 8x8x8 LED cube, all components will be placed on a custom pcb except the programmer. I bought this little programmer a couple weeks ago to program a standalone atmega328p: http://www.ebay.com/itm/380717046158?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2648. I want to use this to program my led cube, however I'm not sure if I'm able to do so. Normally you would connect the tx/rx to the tx/rx of the chip and connect the vcc/gnd from the programmer to the vcc/gnd of the chip. However I want to use an external power supply instead of the power supply of the programmer (only 500mA, so if the cube will light up it won't be able to supply enough current). So I only connect the tx/rx from the programmer to the tx/rx from the chip and share the ground from the programmer with the ground of the power supply, anybody know if this setup is going to work or not?

thanks in advance!
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Anyone smiley-grin?
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I can't open the link (network issue), from your description it should be fine.
Connect DTR thru 0.1uF cap to reset pin as well, or use a seperate reset button.
I do similar here for power.  Jumper lets user select between USB for power, or from regulator for power when USB cable is not plugged in to the MIKROE483 USB Module (under $9 at mouser, no messing with soldering the really small FTDI chip)
http://www.crossroadsfencing.com/BobuinoRev17
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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Ok great. So if I'm right I hook up my external power source and connect the TX, RX, GROUND and DTR pins (and ofcourse leave the VDD pin unconnected) from the programmer to the correct pins of the atmega chip and everything should be ready to go?
So the DTR pin is used to reset the chip after the code is uploaded?? Because I will use a jumper from the reset pin to ground to reset the chip if needed, but I don't want to short the jumper every time if I upload a code  smiley-razz. Thanks smiley smiley
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How is the programmer powered? From the USB side?
DTR is used to software reset the '328 Before programming - gets the bootloader fired up & waiting for serial data to start the programming sequence.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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The programmer itself will be powered through the USB port. However the atmega chip will be powered through an external power supply. I'm not sure if this will cause any trouble smiley.
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No, as long the grounds are connected.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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Okay, you're help was much appreciated smiley-grin smiley-grin
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