Rkreiner
Posts: 4
Joined: Tue Apr 17, 2018 7:32 pm

Microchip/mcu

Fri May 10, 2019 9:35 am

Hi All,

I'm searching for an microchip or mcu that can expand my GPIO with 5 and also drive 8 neopixels via i2c. What is the best, smallest and cheapest solution for this?

Thanks!

Best,
Rasmus

Brandon92
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Re: Microchip/mcu

Fri May 10, 2019 9:46 am

You need to provide a little bit more information. There are a lot of options you can choose from. And what is do you mean with smallest, because there are some MCU that are not easily to solder.

Did you have a look at the website from microchip. They have also more or less a table of the different MCU families, so you can select what you want. And go from there.

Do you have experience with a MCU. If not I would recommend to take a look at the arduino. That chip comes also in a small package.

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mikronauts
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Re: Microchip/mcu

Fri May 10, 2019 1:16 pm

Right now, I think an arduino nano 3 clone would probably suit you. Cheap, usb, tons of tutorials.

You will have to learn how to communicate with it.

You need to be more precise:

"can expand my GPIO with 5" is meaningless.

5 what?
Rkreiner wrote:
Fri May 10, 2019 9:35 am
Hi All,

I'm searching for an microchip or mcu that can expand my GPIO with 5 and also drive 8 neopixels via i2c. What is the best, smallest and cheapest solution for this?

Thanks!

Best,
Rasmus
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

Andyroo
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Re: Microchip/mcu

Fri May 10, 2019 2:39 pm

Have a look at https://hackaday.io/project/8516-picopixel

Something like the ATTiny85 boards from eBay are readily available in all countries and you could use two to give you the extra 5 I/O ports if you do not want to use something like the MCP23017 expander chips.
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markkuk
Posts: 92
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Location: Finland

Re: Microchip/mcu

Sun May 12, 2019 9:32 am

ATSAMD09 with seesaw: 7 GPIOs, up to 340 NeoPixels etc. See the docs: https://learn.adafruit.com/adafruit-see ... iring-test

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mahjongg
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Re: Microchip/mcu

Sun May 12, 2019 12:46 pm

Why use a microchip chip, why not use a standard I/O expander, (often also from microchip), or do you want special features for the "5 I/O's"?

Rkreiner
Posts: 4
Joined: Tue Apr 17, 2018 7:32 pm

Re: Microchip/mcu

Mon May 13, 2019 11:46 am

Hi All,

Thanks for all the replies - there are some very useful directions to pursuit.

Just to clarify what I want to accomplish is to attach 5 backlit buttons to a Raspberry Pi 3 which uses the Pimoroni Hyperpixel display. That display uses all the GPIOs on the RPi, but has its own i2c connection, which I can use to interface with the buttons.

I have the MCP23017, but - as i understand - this cannot drive the neo-pixels, because it can't provide the PWM-signal that is needed.

Eventually it is going to be embedded in a dedicated circuitboard and therefor it would be optimal with a small form factor microchip. However, I also need to have some sort of easy way to change and develop a prototype. Any inputs hereby is more than welcome.

Lastly, there is no reason not to use USB. So if that makes more sense let me know.

Thanks!

Andyroo
Posts: 2834
Joined: Sat Jun 16, 2018 12:49 am
Location: Lincs U.K.

Re: Microchip/mcu

Mon May 13, 2019 12:41 pm

For others reading this thread - Just because all the pins are covered it does not mean they are all used :lol: (see below though)

The best site (please think about supporting it via Patreon) to find out what is actually used is https://pinout.xyz/ and follow the link on the right ‘browse more HATs...’

Unfortunately in your case though, all you have left is ground and power :o :shock: :o display pins used

I would look to using something like a USB to Serial connector to connect from the Pi to something like the Arduino or ESP8266 series of chips and let that take instructions from the Pi and feed back switch status. You could even go WiFi and run MQTT on the Pi and ESP to do the communications for you if you do not want to be tethered.

USB to Serial adapters are very cheap and often sold as part of a kit or built onto the board.

You could look at starting with this board and a suitable adapter. Give the good folk there a quick call or email and they will set you up - I’ve always had great and fast service from them :)
Need Pi spray - these things are breeding in my house...

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