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Testing the GPIO pins
shockr
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#1
08-09-2016, 07:54 AM
Based on the PDF attached to the post at http://forum.pine64.org/showthread.php?t...38#pid1238, I have been able to test all the pins as output by lighting a LED. 

However, I noticed that the LED isn't as bright when I use any of the PL pins. I don't have much experience here so could anyone explain the reason for this?

I also couldn't get PL10 to work at all as the LED wouldn't come on. All other pins on the Pi2, Euler and Exp bus work fine, however. Could this be a problem with my board or is there something I have to set to use this as an output pin?

Just for reference, these are the PL pins I tested
       GPIO   Pin No.
PL10    362    8 (Pi 2)
 PL9    361   27 (Pi 2)
 PL8    360   28 (Pi 2)
PL11    363    7 (Euler)
 PL7    359    2 (Exp)
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MarkHaysHarris777
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#2
08-09-2016, 01:01 PM
I suspect that these pins have built-in current limiting resistors. I know this is true for at least the PL7 GP(359) !

PL7 is the system LED (on the board between the IR module female plug and the power button. (LED on the left)

This is designed for a 3mm low-power 2-4 ma LED. There is a 1000 ohm resistor in-line with this LED built-in. Hence, it is dimly lit (even with a low-power LED).
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martinayotte
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#3
08-10-2016, 09:44 AM (This post was last modified: 08-10-2016, 09:44 AM by martinayotte.)
According to A64_Datasheet_V1.1.pdf, the ports typical voltages are :

VCC-IO,VCC-PC => 3.3V
VCC-PD,VCC-PE => 2.5V
VCC-PG,VCC-PL => 1.8V

(although I didn't check with voltmeter yet)
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MarkHaysHarris777
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#4
08-10-2016, 10:53 AM
(08-10-2016, 09:44 AM)martinayotte Wrote: According to A64_Datasheet_V1.1.pdf, the ports typical voltages are :

VCC-IO,VCC-PC => 3.3V
VCC-PD,VCC-PE => 2.5V
VCC-PG,VCC-PL => 1.8V

(although I didn't check with voltmeter yet)

martinayotte,  thank you for this note;  the question now is the reverse, what are the maximum voltages for these pins on input ?!?   Is the maximum 3v3 on all GPIO pins, or is it (for instance)  1.8v on  PG, and PL ?

Wish we had the latest schematic and datasheet for the 2G A64 +
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martinayotte
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#5
08-10-2016, 01:02 PM
According to the same specs, it seems that all pins can tolerate up to 3.6V
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MarkHaysHarris777
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#6
08-10-2016, 01:38 PM
(08-10-2016, 01:02 PM)martinayotte Wrote: According to the same specs, it seems that all pins can tolerate up to 3.6V

That is the assumption I have worked against ... but then again, I have only ever used the 'normal' GPIO pins on the PI bus...  I am now wondering if those output voltages are programable ?    martinayotte, where are you reading from... is this data sheet on the wiki ?  or in the user manual ?
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martinayotte
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#7
08-10-2016, 05:24 PM
It is coming from http://files.pine64.org/doc/datasheet/pi...t_V1.1.pdf
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MarkHaysHarris777
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#8
08-10-2016, 05:30 PM
(08-10-2016, 05:24 PM)martinayotte Wrote: It is coming from http://files.pine64.org/doc/datasheet/pi...t_V1.1.pdf

thanks
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