What resistor values to allow TPI programming in circuit?

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John_A_Brown
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Posted by John_A_Brown: Mon. Apr 22, 2013 - 12:58 PM
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I have just searched the ATTiny4/5/9/10 datasheet, AVR918 and AVR042 in vain to try to get a feel for what value of resistor I should use to allow the reliable use of the TPI on a Tiny10 chip.
Has anyone got any idea where this information is hidden?

First time I've used an AVR so small that TPI is the only ISP option.

John

Four legs good, two legs bad, three legs stable.

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AVR Microcontrollers, megaAVR and tinyAVR
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John_A_Brown
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Location: Underneath the Cotswolds escarpment, England.
Posted by John_A_Brown: Mon. Apr 22, 2013 - 02:28 PM
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Just to add more information:
/RESET will be fine, as it's unconnected.
I need one ADC input, which will also not be a problem, as I can easily add 5 or 10K of resistor.
One output is driving the base of an NPN, so that also can have a sizeable resistor.
The pin I'm worried about will be either TPIDATA or TPICLK, because I need to drive an LED with PWM, and they are the two possible PWM outputs.

So I suppose my question really boils down to:
Can the TPICLK output from my AVRISP MK2 drive an LED with a series resistor of around 180 Ohms.

Four legs good, two legs bad, three legs stable.

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