Olimex Support Forum

OLinuXino Android / Linux boards and System On Modules => iMX233 => Topic started by: flavigny on October 06, 2012, 12:29:13 pm

Title: Question about connexion of LED on the OlinuxMicro board
Post by: flavigny on October 06, 2012, 12:29:13 pm
Hello,

the LED1 is not documented in the user manual.
I am rather timorous about hardware.


Anyone could confirm how to connect a LED.

I imagine two ways for a "direct" connection:
1) insert the LED  between a GPIO pin and ground (so the current is coming from iMx233, limited by internal resistor of 47 kO)
2) insert the LED between + (3.3V) and the Gpio pin (so the current is absorbed by iMX233 without internal resistor).
Is it mandatory, (or cautious) to add a resistor?  (how many Ohms ?).

Regards
PO.
Title: Re: Question about connexion of LED on the OlinuxMicro board
Post by: Kean on October 06, 2012, 04:46:02 pm
Looking at the schematic of Micro board, LED1 anode is connected to the GPIO, and its cathode connects to GND via a 2k2 resistor.  So the GPIO is sourcing current.  Different resistors can be used based on the Vf of the LED you use and brightness required, but I'd always recommend including one (100R or greater) and not relying on any GPIO current limiting.

Kean
Title: Re: Question about connexion of LED on the OlinuxMicro board
Post by: Fadil Berisha on October 06, 2012, 05:38:58 pm
Quote from: flavigny on October 06, 2012, 12:29:13 pm
Hello,

the LED1 is not documented in the user manual.


You are right, LED1 is listed on page 36 with no description.
This is system LED. Light is solid ON or blinking when kernel take control of system. 

Quote
Anyone could confirm how to connect a LED.


Led is already connected, please refer to Kean's  answer. 

Fadil Berisha 
Title: Re: Question about connexion of LED on the OlinuxMicro board
Post by: flavigny on October 06, 2012, 07:38:02 pm
Quote from: Kean on October 06, 2012, 04:46:02 pm
Looking at the schematic of Micro board, LED1 anode is connected to the GPIO, and its cathode connects to GND via a 2k2 resistor.  So the GPIO is sourcing current.  Different resistors can be used based on the Vf of the LED you use and brightness required, but I'd always recommend including one (100R or greater) and not relying on any GPIO current limiting.

Kean


Ok, it is clear, I will try in a few days.
Regards