ICSP... which way round...

Need to hook an ICSP connector. I'm pretty sure I can identify which pin is which on the board, but the cable could fit on there two ways. I know how to find pin 1 on an IC. Is there a standard way that these connectors are laid out so that I can tell which corner is pin 1?

Grab a multimeter and use this as a reference:

Delta_G:
Need to hook an ICSP connector. I'm pretty sure I can identify which pin is which on the board, but the cable could fit on there two ways. I know how to find pin 1 on an IC. Is there a standard way that these connectors are laid out so that I can tell which corner is pin 1?

usually one side of the ribbon cable has the one outside wire colored different then the other wires color, that different color wire side goes to the pin 1 pin.

Lefty

retrolefty:

Delta_G:
Need to hook an ICSP connector. I'm pretty sure I can identify which pin is which on the board, but the cable could fit on there two ways. I know how to find pin 1 on an IC. Is there a standard way that these connectors are laid out so that I can tell which corner is pin 1?

usually one side of the ribbon cable has the one outside wire colored different then the other wires color, that different color wire side goes to the pin 1 pin.

Lefty

Well I guess it is DMM time cause the colored wire on this one goes to the middle. Although it does come out of the side of the connector on the other end. But that one is obvious which way it goes because it has a little tab and only fits one way.

Yes, his problem is he doesn't know which way the cable's connector goes as it will fit both ways.

I'd use a logic probe if I had one to identify VCC and GND, that will tell you the orientation.

Nice pinout image too, I have saved that.

Actually it's pretty fool proof if the cable is using flat ribbon wire as it can go either way as long as both ends have pin 1 on the same edge of the flat ribbon cable. Where it gets more dicey is if it's a round cable assembly.

Lefty

Delta_G:
Need to hook an ICSP connector. I'm pretty sure I can identify which pin is which on the board, but the cable could fit on there two ways. I know how to find pin 1 on an IC. Is there a standard way that these connectors are laid out so that I can tell which corner is pin 1?

Just use an ohm-meter and find the pin that's ground. Pin 1 is diagonally opposite.

       ___ pin 1
      |
*  *  *
*  *  *
|____gnd

Is it on the arduino or the programmer you cannot determine pin 1?
Programmers usually have a keyed header so you can only insert the cable one way and the cable normally has one edge coloured to denote pin 1. The UNO board has a dot at one corner of the ICSP headers that denotes pin 1.

Riva:
Is it on the arduino or the programmer you cannot determine pin 1?
the cable normally has one edge coloured to denote pin 1.

I've seen plenty that don't and the mark on the PCB is less than obvious. In the absence of a keyed box around the pins, five seconds with a multimeter could save you a world of pain.

Also, as a practical matter, the AVR ISP II doesn't seem like it will fry your board if you get the polarity reversed. I've done it before and it hardly draws more than a few mAs under those conditions (my bunch supply tells exactly how much current is going out). So there is some protection built in. The main thing is it doesn't work, so you turn it around.

JoeN:
Also, as a practical matter, the AVR ISP II doesn’t seem like it will fry your board if you get the polarity reversed. I’ve done it before and it hardly draws more than a few mAs under those conditions (my bunch supply tells exactly how much current is going out). So there is some protection built in. The main thing is it doesn’t work, so you turn it around.

Well the AVR ISP mark II doesn’t (can’t) try and power the target chip so it’s not as vulnerable to mis-wiring. Most of the other common AVR isp programmers tend to have a clip or are hardwired to provide Vcc power to the target.

I too have plugged the 6 pin ISP cable in backwards a couple of time to arduino target boards using ISP programmers that do power the target and had no lasting bad things happen, although I try not to make that a habit and I corrected it as soon as I noticed the power led didn’t light on the target.

Lefty