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Topic: Doubling up ICSP pins - recommendations? (Read 2 times) previous topic - next topic

Marvin Martian

Just what I was looking for! Thanks!

Coding Badly

Mar 22, 2013, 01:58 am Last Edit: Mar 22, 2013, 06:54 am by Coding Badly Reason: 1
Sorry - USBTinyISP...

The USBtinyISP includes 1.5K series resistors which will limit the current when there is a wiring problem but will also create a voltage divider with things like an LED + resistor.  If you use a programmer that does not include series resistors (or the resistors are a lower value), you will be able to have a wider variety of things connected to the ISP pins.  For example, I routinely use an Uno as a programmer and have never had a problem with LEDs on the ISP pins.


You're very welcome, those links helped me a lot, also, as stated in one of the examples on the first link (see note) and just as used in the arduino uno rev 3. using a buffer allows you to really add more uses to your icsp pins like being able to read an input and still program your device. will do on my next arduino clone board revision. Have fun! 8)


Mar 30, 2013, 09:10 pm Last Edit: Mar 30, 2013, 09:14 pm by Docedison Reason: 1
I only buy LED's with 15 - 20 candela output and I've found that a 10K current limiting resistor provides enough light from the 20 candela LED's to be useful with normal room lighting. I build devices that are battery operated and low current is a requirement. I just plugged a green LED into a breadboard. Cathode grounded a 10K resistor from +5V (4.1Vdc measured) and measured 2.5V across the LED subtracting that from 4.1V = 1.6V divided by 10000 = 160 uA and provides a visible light that could be more visible and draw half the 160uA too if it was pulsed off and on at a 50% duty cycle. There is a small increase in price for the 5 mm high output LED's.. I buy the 5 color assortments and surprisingly the light output from batch to batch has been strangely uniform... An odditie when buying loose parts from China.. IMO

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