Using an USB2Serial module with an ATmega1284 powered with LIPO battery

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1

Please, I need some feedback on the following question:

I successfully built a standard ARDUINO STAND ALONE circuit using an ATmega1284 chip. For serial communication, I used a Sparkfun USB2Serial Breakout FT232RL. Normally, the VCC pin of USB2Serial would power the ATmega chip (I tried and it works).

Now I need to add an external power supply as a Lipo 3.7 V. I would connect the battery to VIN pin of a
Pololu S7V7F5 Step Up/Down voltage regulator, which furnish 5V in the OUT pin. Then I would connect Pololu OUT pin to VCC and AVCC pins of ATmega1284.

Question: in order to avoid a dangerous double power supply (from USB2Serial module and Lipo) I would remove the VCC from USB2Serial module, do you think it is ok? Please find in attachment the circuit I built (I did'nt try it yet).

Thanks,
Valerio

POWER_CIRCUIT.png
POWER_CIRCUIT.png1935×1200 312 KB

2

Question: in order to avoid a dangerous double power supply (from USB2Serial module and Lipo) I would remove the VCC from USB2Serial module, do you think it is ok? Please find in attachment the circuit I built (I did'nt try it yet).

I don't understand the reason for your question. You can see there is no power coming out of the USB Serial adaptor (no wire connected to Vcc pin) so why are you asking this question ?

3

I apologise, maybe I was not clear: I was wondering if the circuit I designed was ok, as I did'n t test it yet (and I'm a newby in electronics). Normally USB2SERIAL would furnish power to ATmega, so I was not sure if the serial communication would be ok without VCC connection. By the way, from your response I understand it is ok, i'll test it tonight!
Thanks,
Valerio

4

Hi Valerio,

Should be fine as long as the ground is still connected between your breadboard and USB2SERIAL (I can see it is in your diagram)

Cheers
Richard