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Author Topic: Arduino UNO: D11, D12 and D13 after reset pulse  (Read 650 times)
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I notice there is a 3 pulses/spikes on the UNO D11 (MOSI), D12 (MISO) and D13 (SCK) each time i press the reset button.
This is not observed in other IOs.
All above IOs are set as output.

D11 - 1.5V spike, 124ms between each
D12 - 3V spike, 124ms between each
D13 - 5V pulses, ~8Hz, 124ms pulse width (50% duty cycle).

Anyway to prevent this?
I used these pins at OUTPUT to trigger another circuits.
This caused false trigger when power up or reset.

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You could try 1K to 5K to 10K pullup or pulldown resistors so the pins are not floating immediately after the reset.

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