Supplying +5v with USB AVR Programmer

[saucisse]

My ‘‘target box’’ needs to be feed with a +5Vcc in order to function. I just found out that the Pololu USB AVR Programmer does not supply power to the target device

Looking at this picture, we can see that there is a +5v source on the programmer board…could I just solder a wire from that VBUS (+5v) point to the VDD pin of the connector? This way I could supply 5 volts to +Vcc pin of the ‘‘target box’’ ?

My ‘‘target box’’ used to program Atmega48-128 chips for my quadcopter flightcontroller:

Thanks for the help!

Sebastien

[saucisse]

Well I guess I found the answer in the user’s guide:

2. VDD: An input line that the programmer uses to measure the voltage of the target AVR. While programming
the target device, the programmer uses this line to constantly monitor the target VDD. If the voltage goes too low
or varies too much, then the programmer aborts programming in order to avoid damage to the target AVR. Section
3.d has more information about target VDD monitoring. The VDD line is not used to power the programmer; the
programmer is powered from the USB. This line cannot be used to power the target device; the target device must be independently powered for programming to work.

[DavidEGrayson]

The line from the user’s guide that you highlighted is talking specifically about the VDD line, not the VBUS (+5V) line. You can use the VBUS line to power your AVR if you want, but just be aware that this line is directly connected to the 5V power source of your USB port. So don’t short it to any other power sources, and don’t draw more than your USB port can handle. It you draw less than 100 mA from it you will probably be OK.

–David

[Josef_Huttner]

Hi,
I am thinking of using Vbus of the Pololu Usb Avr programmer to power up the 3pi during programming.
With batteries inside, where would you recommend applying the 5V for safe programming?

• the charge connector?
• Vcc
• Vbatt

Thanks.

Josef