# Can I customize the blink function? (It does not shine in CM3) **URL:** \ **Category:** balenaOS\ **Created:** [July 13, 2019, 12:42am UTC](https://forums.balena.io/t/can-i-customize-the-blink-function-it-does-not-shine-in-cm3/19695 "2019-07-13T00:42:09Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Keisuke](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/keisuke/32/1108_2.png) [@Keisuke](https://forums.balena.io/u/Keisuke)\ **Post date:** [July 13, 2019, 12:42am UTC](https://forums.balena.io/t/can-i-customize-the-blink-function-it-does-not-shine-in-cm3/19695/1 "2019-07-13T00:42:09Z")
There is a `blink` feature for identifying terminals. On the Raspberry pi, the board’s LED flashes. However, the Raspberry pi CM3 has no LED. We have attached the power supply LED in GPIO. If you can customize the call of `Blink`, you can blink it with GPIO, etc. Is it possible? ---
**Author:** ![imrehg](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/imrehg/32/36_2.png) [@imrehg](https://forums.balena.io/u/imrehg)\ **Post date:** [July 15, 2019, 7:31am UTC](https://forums.balena.io/t/can-i-customize-the-blink-function-it-does-not-shine-in-cm3/19695/2 "2019-07-15T07:31:27Z")
Hey @Keisuke, what do you use as a base board / carrier board for the Raspberry Pi CM3? In the case of the Compute Module, the LED is on the base board, and the LED action depends on the specific carrier board. For example our [balenaFin](https://www.balena.io/fin/) has an LED that is blinked, and the balenaFin variant of the OS sets the correct device to use for the blink action. As I checked, both for the Raspberry Pi 3 device type, and the balenaFin device type the blink device is `/sys/class/leds/led0/brightness` (which is set in the `LED_FILE` variable of `/etc/resin-supervisor/supervisor.conf`). In your case it really depends on the hardware you use, and would appreciate if you can provide some more information on that, before we can give any more advice. Also, what balenaOS version / device type are you flashing on the CM3 you have? In general the `blink` action is fixed for a device type, as not expected that an OS version is flashed on another device type it is not created for. ---
**Author:** ![Keisuke](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/keisuke/32/1108_2.png) [@Keisuke](https://forums.balena.io/u/Keisuke)\ **Post date:** [July 23, 2019, 11:27pm UTC](https://forums.balena.io/t/can-i-customize-the-blink-function-it-does-not-shine-in-cm3/19695/4 "2019-07-23T23:27:59Z")
Hello @imrehg Thank you for answering. We are connecting to our own custom boards. The LED indicating that the power supply attached to the main unit is ON is connected to GPIO. Is it possible to blink the LED connected to GPIO by rewriting the indicated file? ---
**Author:** ![telphan](https://avatars.discourse-cdn.com/v4/letter/t/ba9def/32.png) [@telphan](https://forums.balena.io/u/telphan)\ **Post date:** [July 24, 2019, 8:48am UTC](https://forums.balena.io/t/can-i-customize-the-blink-function-it-does-not-shine-in-cm3/19695/5 "2019-07-24T08:48:52Z")
Hi, What balenaOS version / device type are you flashing? Kind regards, Theodor ---
**Author:** ![Keisuke](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/keisuke/32/1108_2.png) [@Keisuke](https://forums.balena.io/u/Keisuke)\ **Post date:** [July 24, 2019, 3:16pm UTC](https://forums.balena.io/t/can-i-customize-the-blink-function-it-does-not-shine-in-cm3/19695/7 "2019-07-24T15:16:38Z")
hello It is as follows. OS: balenaOS 2.32.0 + rev1 Device type: Raspberry Pi 3 ---
**Author:** ![chrisys](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/chrisys/32/1731_2.png) [@chrisys](https://forums.balena.io/u/chrisys)\ **Post date:** [July 24, 2019, 6:42pm UTC](https://forums.balena.io/t/can-i-customize-the-blink-function-it-does-not-shine-in-cm3/19695/8 "2019-07-24T18:42:07Z")
Hi there, in that case you should be able to edit the file mentioned above as my colleague suggested. It is likely that you’ll need to modify the `/etc/resin-supervisor/supervisor.conf` file before it is flashed to the device.