FTDI with Atmega 328P-PU question

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1

We wanted to know if we are using a 5V battery power source and we needed to wire up the FTDI chip but did not want to use the 5V USB power. We would just connect DTR, RX, TX, CTS and leave GND and 5V pins disconnected?

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3

Your external power source should be around 7-12 Volts not 5.

I don´t quite understand what you are trying to do, you want to power your arduino via external battery and plug in some usb device to communicate with ?

4

Thanks spy, got it working just fine. Smithy we are running a 8 volt battery to a regulator to the atmega chip. We did not want the USB 5v to interfere but we still wanted to be able to debug through serial.

PS. I am not sure why but we do not have GND connected only CTS and it works fine.

5

amano001:
PS. I am not sure why but we do not have GND connected only CTS and it works fine.

Oh dear!

6

amano001:
PS. I am not sure why but we do not have GND connected only CTS and it works fine.

But for how long...?

7

Why would you power an arduino externally and use usb only for serial debugging (i don´t quite get the sense) ?

8

Maybe they want more current - USB only good for 500mA, barrel jack can support more.

9

CrossRoads:
Maybe they want more current - USB only good for 500mA, barrel jack can support more.

Barrel jack can not - limited by thermal capacity of regulator.

In this case, a "5V battery power source" was specified - now there seems to be some ("urban") mythology that it is somehow dangerous to use USB and 5V external power simultaneously. If Vcc was connected to a battery there may be some tendency for the USB to charge, say, a 4.5V set of alkaline batteries which might be a concern if left connected for a significant period of time - but should be perfectly fine for half an hour or so.

10

Well for instance we are not running an arduino, we are running an Atmega 328 that we bootloaded and we are using a NTE 5V regulator. We are running motors that require 2-3A and need an external source....like he said 500mA is not enough to run certain things also we have a lot of sensors that we want to be able to debug still while motors and such are running.

PS I connected GND =p

PSS I am