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SAMA5D27_SOM1_EK RGB Led Circuit

Posted: Wed Nov 27, 2019 3:26 pm
by oyildirim
Hello,

First of all, I searched forum about this weird situation (Maybe forgotten may it has a meaining).


I am designing my custom board and I want to use same circuit for RGB boot leds.
I have the document 03-10759-RD2.PDF which is in the SAMA5D27-SOM1-EK1_REVD2 Design and Manufacturing Files\REVD2\Project_Outputs\DevTools folder.

But here is the thing I want to be sure on page 8 (LED circuit):

1) There is a 10K resistor (R133) connected to ground between PA31 and 100R (R136) connection
2) There is a 10K resistor (R137) connected to ground between PB1 and 100R (R135) connection
3) There is NO resistor connected to ground between PA10 and 100R (R134) connection


(I wanted to upload circuit image here but I couldnt, sorry)


Why is there NO 10k resistor right before PA10?

Best regards,

Onur

Re: SAMA5D27_SOM1_EK RGB Led Circuit

Posted: Sat Nov 30, 2019 2:32 am
by blue_z
I'm not a board designer, but those look like resisters to limit the current, i.e. current dividers versus a dropping resister.
Apply Kirchhoff's current law.

Study the datasheet of the RGB LEDs. The green and blue LEDs are probably more efficient (i.e. need less current) than the red.

Regards

Re: SAMA5D27_SOM1_EK RGB Led Circuit

Posted: Tue Jan 07, 2020 8:56 pm
by oyildirim
Thank you. I designed my custom board using SAMA5D27_SOM1 similar to evaluation kit. I put a 10K resistor for voltage divider (in case needed) and I see that no red led directly lights up. If you dont solder the 10k resistor, the board powers up at the same time with red led.

Thank you,

Onur

Re: SAMA5D27_SOM1_EK RGB Led Circuit

Posted: Wed May 06, 2020 6:06 pm
by gastonn
Hello!

I am also wondering to design my own board with same ARM processor of the SAMA5-D27-SOM1 EK1 board. I just want to let the ethernet port, RGB led, and RS485 connection of the board. Please are there any intersting documents or something that could help me ?
I will be grateful!