I have 8 x 20ma status LEDs and all of them may be on all the time. Which USB microcontroller that can be communicated with via serial would be best? If sacrifices have to be made, I'd prefer to sacrifice power efficiency for a smaller footprint.
I'm not proficient with any of them but I've used various ATMega's, ESP32 and ESP8266 boards. However, I've never tried to use 8 pins at once to power something nor have I paid attention to which boards have good low power and/or 8 free pins to use.
What is the maximum size that will still be acceptable ?
50mm x 40mm x 13mm.
Basically the size of a Nano or Pico or similar but it can be wider. I think this is pretty large but since I need USB to communicate, I guess it's medium'ish for something with 8 free pins...?
An Arduino Pro Mini (~$4.00) is shorter and slightly wider than a NANO.
It requires an FTDI module to program it (~ $5.00, this can be used on other Pro Minis).
I have the MHETtiny88 running a 300 neopixel marquee for over a year. Programs are anything I use on a Nano (programming requires "upload before connect" for handshaking to work.)
I assume that you read a datasheet and are concerned about the bit where the maximum TOTAL I/O current is mentioned (something like 100mA on an avr, which is significantly less that 8 * 20mA…
You should consider that modern LEDs are much brighter than in the old days, and it’s a rare indicator led that needs as much as 20mA. The built in leds on an Uno run 2 to 6mA, for example.
Thank you for the responses.
I should of stated powered and communicated with via USB. This will go into a small thin client sized computer and I won't have opportunity for communication that isn't hosted by USB (the motherboard doesn't have a 9 pin d-sub for serial or a GPIO).
@westfw: they're 3mm leds and I believe the max is 12mA a piece, but hopefully they won't be a problem.
I didn't know that so I've changed to 2mA red LEDs and they seem plenty bright enough for my needs. I didn't know they made 2mA LEDS :-/. So thanks for this, now I feel I can run this more confidently on various MCs.
I've been using a D1 ESP32 and a shift register but mainly because I need to plug the board directly into the USB 2.0 header on a motherboard to both power and communicate with it. It is in that, that I'm looking to shrink down in terms of power draw.
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