[ell-i-developers] Re: Recommendations for MCU for Led driver?

  • From: Pekka Nikander <pekka.nikander@xxxxxx>
  • To: ell-i-developers@xxxxxxxxxxxxx
  • Date: Wed, 4 Jun 2014 18:11:08 +0300

> I'm designing microcontroller-controlled LED driver. I need to select a
> suitable MCU for project. My requirements are: Absolute minimum of 2
> 16-bit PWM channels, 3 strongly preferred and 6 would be enough for all
> purposes I can foresee right now. Frequency "as high as possible", at
> least over 50 kHz.
> 
> MCU should have an ADC channel for each PWM-channel, muxed ADC with low
> samplerate is ok.
> 
> MCU also needs SPI-lines for communication with outside world.
> 
> Does someone have experience with suitable microcontroller? Any
> recommendations for selection?

I would recommend STM32F030F4P6 or STM32F050F4U6

http://www.digikey.com/product-detail/en/STM32F030F4P6/497-14044-5-ND/4357517
http://www.digikey.com/product-detail/en/STM32F050F4P6/STM32F050F4P6-ND/4357518

In medium quantities their prices go pretty low, even at Digikey, USD $0.58 for 
030 and USD $1 for 050, in full reels.

Both have a number of 16 and 32 bit PWM channels, mutexed ADC channels with 
maximum of 1 Mbps sample rate (at around 9-10 bits/sample in practise), I2C, 
SPI, and USART.  Both are directly compatible with the Ell-i runtime, even 
though adding support requires some minor adaptation work, as we currently 
support only STM32F051 fully.

However, as a caveat you should check if the 20-pin F4P TSSOP20 package is has 
enough of pins for your purposes, and if the supported pins provide the right 
functionality.  For 030 there seems to be 9 ADC channels multiplexed with SPI 
and Timer/Counters, SWD, and USART/I2C/Timer Counter.  In practical terms you 
would probably want to use 4 pins for SWD and USART/I2C, and divide the 
remainder 9 pins between ADC channels and PWM outputs.  If needed, the 2 
USART/I2C pins can also be repurposed for PWM outputs.  

If that is too few pins, the next choice is the 32-pin LQFP32 (K4T), but they 
are not readily available at DigiKey in small quantitities.  For prototyping 
purposes the 051 version would be good enough:

http://www.digikey.com/product-detail/en/STM32F051K4T6/497-13623-ND/3947375

C4T is not much more expensive and has even more pins:

http://www.digikey.com/product-detail/en/STM32F051C4T6/497-12947-ND/3193382

--Pekka

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