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Ralim
LED power and possible SPI connectivity
Was asked to write an issue (by River B.) on adding controllable LED lights to the Pinecil V2. Have a design with just power currently and wonder if utilizing the empty U10 pads would work for PWR and GND? If that does not work the discord folks said the 5V rail might be an option as well and where is the best place to connect to that then?
In discord someone wanted SPI controlled LEDs and I would like to know where is the best place to connect to SPI and if it would be possible for the OS to support them?
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This link is the LED Brian suggested because " they're really bright, really small, and use SPI for connection to the MCU. the internal pinecil bus has SPI, so it should be pretty easy to connect them." https://www.aliexpress.com/item/2261799828543945.html
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For reference, this is the front and back image of the design Herushan made for LED light for Pinecil. the idea is to slip it onto the plastic ring of the handle right where the Tip inserts so swapping tips will not be an issue.
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It has resistors on the back side, and Just 2 LED total, one on left and the right, possibly SMD leds.
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Originally, idea was to tap into the 5V rail as other people have done for 1-2 LEDs in the past (drilling a small hole into the plastic side). some people thought connecting to SPI would be good also, trying to figure out if that is worth doing.
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One goal is to have a viable repeatable DIY solution with instructions that people can use for pinecil. maybe in the future even have a spot on the PCB ready-made like the hall sensor, and a resistor on the PCB already.
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LED light on Pinecil is a popular idea whether it's a DIY ready-made solution or Pine64 adds it permanently in the future. imagine working under the Dashboard of a car to solder something.
Hia,
Absolutely you can tap power off U10 to the best of my knowledge. You should otherwise be able to find a 4-5V regulated rail after the DC/DC that you can use as well.
In terms of controlling the LED's; Ill need to check if we have the hardware SPI exposed anywhere. If its possible to map the hardware SPI pins out; definitely happy to look at adding support.
@Ralim there is a 4.2V rail on the schematic. There is also 3.3V regulator. Nusacat mentioned the 3.3V reg has a 300ma limit, how much is left? Could we use either 3.3V or the 4.2V rail or should we skip the 3.3V rail for only the 4.2V for power on LEDs?
If possible I would use the 4.2V rail. There should be headroom on the 3.3V rail but wouldn't want to risk instability.
@Herushan / ahall made the first protptype LED light today for Pinecil V2, red wire is going to CAP C8 for 4.6v and black wire is going to GND leg of unused U10 spot.
since it is GND, he thinks it should also be okay for V1 original owners to also use the same U10 spot/pin for GND even though U10 is occupied by TMP sensor in all V1's. He was concerned about using U10 for power bc of affecting readings for V1 users and it was not clear on schematic what voltage is U10. For now he just soldered to side of C8 CAP for 4.6V power.
if we can not use SPI to control on/off then another possibility is small on/off switch on the bottom.