Good morning everyone,
I'm using my arduino nano for a project featuring all 6 pwm pins to control independently led lines (unfortunately yes, i cannot work with integrated led panels with a separated controller for each led color PWM regulation, i have to control them independently from the arduino itself) and i just realized i might need a 7th PWM pin.
This led me to look at the pinout of a nano board and saw how the pin 17, MOSI of the ICSP interface, is written as a PWM pin itself, but i'm not so sure about that as i could not get any info on how to use it.
I read that its cause they are cross connected to another arduino pin, for example PIN17 should be connected to PIN15 (D11), but i do not understand if cross connected is "reversible" or if they are actually the same pin, simply in different positions.
For anyone wondering, i'm working on a 6 lines LED panel to treat plants with different light compositions and intensities under a stereo-microscope. This panel is particular in dimension, shape and led density, so i cannot rely on a classic grow light panel with its own processor modulating the leds. The system itself with the 6 led lines panel works a charm, but i was thinking about connecting another smaller panel of 5 leds of a different wavelenght to stimulate the plants with specific lights from a different direction, seeing as it could interfere with their phototropism. This would be incredibly cool, but if possible i would prefere to not switch to a whole different board (i have already repared all the shields and boards for the system, i would have to make it from scratch again). In the worst scenario i could get another nano to crosstalk to the first one, controlling the other lights, but we will see.
By the way, this is the schematicsi was talking about before
Much thanks to anyone that will try to help me!
Microcontroller pins can have multiple functions. Usually the GPIO pins (D1..., A0...) are unique to each controller. PWM and SPI are alternative functions which can be available on different GPIO pins with every controller. That's why some controller pins appear as specific pins on a header, e.g. SPI and I2C, while these are only duplicates of some GPIO pins. You only can use one of the alternative functions of a controller pin at the same time.
There are specialized IO Expander chips which, for example, are written to using I2C and provide 8 additional PWM pins. Many of these chips are available on breakout boards and could possible be easily added to your project without losing much of what you have already accomplished. Attach the breakout to the Arduino I2C, attach the breakout somewhere inside the project case, attach the additional LEDs to the breakouts PWM pins, enhance the programming and voila!
The Arduino Mega has 15 PWM pins.
Thanks everyone for the answers! I will find an expansion board for the nano and thinker a bit with that, but will definitely upgrade to a mega in the near future for these kind of experiments. Cheers!
Try this one with an I2C interface
Or for the faster SPI interface the
But you can also get the MPC9685 as just a chip. I have soldered two of these on headers, for easy mounting in a 28 pin IC socket.
One of the simpler surface mount chips to deal with.
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