Using a programmer...

The Pebble is an Arduino-compatible board with a bunch of built in sensors and other devices, including support for ZigBee wireless mesh networking. Great for datalogging or general experiments.
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mibus
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Using a programmer...

Post by mibus » Tue Apr 10, 2012 12:15 pm

Hi,

I have a USBtiny ISP, that can talk happily to an ATmega328 on a breadboard, and to the Pebble v2's onboard 8u2 via the ISP header.

However, it can't seem to talk to the ATmega328 on the Pebble v2 via it's ISP header.

Is this an expected side-effect of loading up the matching digital pins with LEDs, or am I just doing it wrong?

Thanks;
--mibus.

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jonoxer
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Re: Using a programmer...

Post by jonoxer » Tue Apr 10, 2012 12:58 pm

Aha, yes, there's a gotcha in that!

I recall some discussion at the Arduino Miniconf about that problem, and if I recall correctly it's because the pins in the ICSP header for the main MCU are loaded by devices connected to them. Looking at the schematic now I can see that a couple of the pins are pulled LOW by 1K resistors for the open-collector outputs, and one of the pins is pulled LOW via the blue element of the RGB LED and a 330R resistor. That's pretty aggressive biasing for the programmer to overcome.

I haven't looked at the PCB traces to see how practical it is, but you can probably un-load the ICSP pins by cutting the tracks to the RGB LED and the OC outputs.

Something for the to-do list on the next rev of the Pebble!
--
Jon

mibus
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Re: Using a programmer...

Post by mibus » Thu Apr 12, 2012 3:41 am

For now I'll stick with a breadboard - I'd just thought the Pebble would be a handy way to make sure I didn't mess up the wiring. (My first breadboard attempt had +5V and GND backwards. OOPS!).

I've cut up some old prototyping board to make a breadboard-compatible 328 "programmer helper" - ie., plug the ISP cable on the top, and the helper plugs into the breadboard over the chip (with all the wires going to the right place).

I'm waiting for a delivery ATM... because I'm all out of nice headers to use for it. Should be fixed soon enough though ! :)

Thanks Jon!

mibus
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Re: Using a programmer...

Post by mibus » Thu Apr 12, 2012 5:47 am

Forgot to mention in the other post.... one possibility for the v3 is doing what the LaunchPad board does for its on-board LEDs - simply having jumpers in-line, so you can easily remove them if you want access to the pins without the LEDs being in the way.

mibus
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Re: Using a programmer...

Post by mibus » Wed May 16, 2012 10:51 am

mibus wrote:I've cut up some old prototyping board to make a breadboard-compatible 328 "programmer helper" - ie., plug the ISP cable on the top, and the helper plugs into the breadboard over the chip (with all the wires going to the right place).
FWIW, I've now got a PCB made for the ISP->Breadboard adapter for the 328. (I've also got an ATtiny85 version).

Pic here: https://twitter.com/#!/mibus/status/202 ... 24/photo/1 :)

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jonoxer
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Re: Using a programmer...

Post by jonoxer » Wed May 16, 2012 11:51 am

Nice work, @mibus! That looks really cool.

On the subject of programmers, we're about to go into production with our own USB-ASP compatible ISP programmer. It'll probably be available in about a month or so, and it's looking pretty cool.
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Jon

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Re: Using a programmer...

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