AVR ISP MKII Modification to provide power to circuit being programmed

Using Arduino Microcontrollers
#1

I encountered this mod, http://www.eevblog.com/2011/03/25/eevblog-158-avr-isp-mk2-lm317-regulator-tutorial/, that allows the AVR ISP MKII to actually power the circuit being programmed. This is one feature I like about the PicKit2/3, that I missed on the AVR ISP MKII. While he used an LM317, he analyzed its performance, and it seems clear that a low drop-out regulator would work much better. So for my attempt I used a TLV2217-33 instead of the LM317.

Since I don’t like dead bug assembly (like used in the link) I went ahead and created a very simple circuit board using toner transfer method. The mod requires a LDO regulator, two caps (I used 0.1uF), and two switches (1 SPST, and 1 SPDT). The SPDT switch lets you chose between 3.3V or 5V for the circuit being programmed. The SPST lets you connect/disconnect USB power from that circuit, so when in the off position the programmer works as it would normally.

Easy mod, that so far has been working very well. I am attaching a few pics that might explain it better–though I do recommend watching the video in the above link.

Power-brd.tif (1.03 MB)

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#2

Seems so simple, gotta wonder why Atmel doesn't make that a standard part of the design.

#3

CrossRoads: Seems so simple, gotta wonder why Atmel doesn't make that a standard part of the design.

I thought so as well. In thinking about it I suspect that the reason was cost. You need to have the ability to switch off the power, so it would add some cost. I know that when Microchip came out with the PicKit3 they initially did not have firmware support for providing power. It was something they added later when people complained. And the method they use isn't as convenient as it was with the Pickit 2

#4