Running the sketch without the USB cable connected to the PC

Hi,

I am currently working with the DFrobot Bettle board (no bluetooth)
and I have it connected to the ESP8266 WiFi module. I can upload the
sketch via the Arduino IDE and run it successfully with the USB cable
connected to the PC. I am basically using Serial (Rx and Tx) to send
commands to the ESP8266 within the sketch.

However, when I want to use the setup without the USB cable (i.e. by
just having the two boards connected to an external power supply),
then nothing happens. It seems as if the Beetle board is just sitting there.

I followed the Arduino FAQ where it says:

"Why doesn't my sketch start when I'm powering the board with an
external power supply?

Because the RX pin is unconnected, the bootloader on the board may be
seeing garbage data coming in, meaning that it never times out and
starts your sketch. Try tying the RX pin to ground with a 10K resistor
(or connecting RX directly to the TX pin)."

But unfortunately, I am not sure if I can connect Rx to ground via a
resistor, because I have Rx connected to the Tx of ESP8266 for the serial
communication purposes.

I m basically not sure how to run the DFrobot Beetle microcontroller
board (connected to ESP8266) without the USB cable to the PC.

Any help is most welcome.

(If you need any more information than this, please let me now, I ll be happy to provide it)

Adi

Will the program (or any program) run properly with external power if the ESP8266 is disconnected. That should identify whether your use of the Rx and Tx pins is the problem. I have never had a problem with external power but I have never had anything connected to Rx and Tx.

What do you mean by "the two boards" - are you using 2 Arduinos? Have they both got ESP8266s?

Have you considered using SoftwareSerial to communicate with your ESP8266s - that would leave Rx and Tx free.

How are you powering the ESP8266 - AFAIK they require a lot more current than the Arduino 3.3v pin can provide.

Post your code.

...R

But unfortunately, I am not sure if I can connect Rx to ground via a
resistor, because I have Rx connected to the Tx of ESP8266 for the serial
communication purposes.

Tx and Rx refer to the USB connection i.e . Your ESP8266 are connected via the separate serial1 port . Correct?