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I am a software guy (everyone immediately downvotes...) trying do the following:

(1) On a BeagleBone Black ("BBB") I am driving a GPIO pin high in software.
(2) Then I am sending PCM (audio) out another pin as I2S serial.

I want to measure the time between (1) and (2). Of course I could use an oscilloscope, but I want to do the measurement 1000 times and take an average. So I plan to use an Arduino as a timer (I've already written and tested the software using push-buttons as inputs). My question: how do I connect the BBB to the Arduino?

I realize I must connect the GPIO pin of the BBB to an input pin on the Arduino. And the I2S serial pin of the BBB to another input pin on the Arduino.

Is that it? Do I connect the GND of the BBB to the GND of the Arduino as well? And do I need to worry about the 3.3v output from the BBB (both pins) to the inputs on a 5v Arduino?

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  • \$\begingroup\$ You might need to convert 3.3V to 5V \$\endgroup\$ – Mahendra Gunawardena Jun 29 '15 at 1:54
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Arduino expects a minimum of 0.6 * 5 V = 3 V at ts input to detect it as logic high. There is no harm in trying once by connecting directly from BBB to Arduino. Connect both the grounds. If the voltage dips below 3.1 V for some reason, you can go for 3 V to 5 V voltage translator. It should work without translator.

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  • \$\begingroup\$ My friend claimed if I accidentally set the Arduino to OUTPUT instead of INPUT, I will fry my BBB. True? \$\endgroup\$ – Fixee Jun 29 '15 at 3:49
  • \$\begingroup\$ @Fixee only if your BBB has a "HIGH" output level, while the arduino has a "LOW" output level. This would create a short circuit between the VCC 3.3V rail on the BBB to GROUND through the wire and the Arduino's GROUND connection. The damage would most likely occur at the BBB's GPIO output driver, probably destroying the output FET. This just means that pin (or possible the entire port) will not operate correctly from now on. The most likely result is that pin cannot go output HIGH anymore, because the connection from VCC to the output pin has burnt out \$\endgroup\$ – KyranF Jun 29 '15 at 3:55
  • \$\begingroup\$ @Fixee to avoid frying, a 330 ohm resistor can be used between two pins. The drop will be insignificant (330 Ohms * ~10 uA = 3.3 mV), but the protection provided will be significant. Needless to say, even by mistake if a BBB output (High) is connected to BBB output (low) GPIO gets fried. \$\endgroup\$ – User323693 Jun 29 '15 at 4:34

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