micro:bit pin extension

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unvercifcti
Posts: 2
Joined: Mon Dec 18, 2017 11:32 am

micro:bit pin extension

Post by unvercifcti » Mon Dec 18, 2017 11:38 am

Hi,
I want to control four servos with a micro:bit (microbit.org). There are three pins on it. How can I extend one of the pins for instance using ICs and a breadboard?
Thank you.
Ünver

paulvha
Posts: 240
Joined: Sat Nov 11, 2017 2:39 am

Re: micro:bit pin extension

Post by paulvha » Tue Dec 19, 2017 4:58 am

you could look to use the XOR chip.e.g. a 7486.
Connect pin 0 to 1 input on each of the 4 XOR-gates, connect pin 1 to the other input on 2 XOR gates and connect pin 2 to the other input of the last 2 XOR gates. Follow the HIGH/LOW logic as defined for XOR gates and prevent the condition where BOTH pin1 and pin2 are either LOW or HIGH at the same time. Now you can select each servo separate depending on the level of pin 0, 1 and 2.

extra info : If you really have to build it, the 3V from the Micro:bit is not enough for the 7486, it needs 5V.

unvercifcti
Posts: 2
Joined: Mon Dec 18, 2017 11:32 am

Re: micro:bit pin extension

Post by unvercifcti » Wed Dec 20, 2017 2:19 pm

Thank you for your reply. What I want is make a robotic arm accessible to kids. When I use solely micro:bit, they could just use a usb connection.

darrellg
Posts: 321
Joined: Fri Oct 17, 2014 10:02 am
Location: Southern California

Re: micro:bit pin extension

Post by darrellg » Thu Dec 21, 2017 4:45 pm

There are more than three pins on a micro:bit. There are three big ones that can be used with an alligator clip, but the small ones are data pins as well. Some of them are used with the LED matrix, but that doesn't mean you can't use them externally as well. If you get a kit with an edge connector, you can easily take advantage of the additional I/O.
microcontrollers_edge_connector.jpg

darrellg
Posts: 321
Joined: Fri Oct 17, 2014 10:02 am
Location: Southern California

Re: micro:bit pin extension

Post by darrellg » Thu Dec 21, 2017 4:47 pm

Sparkfun sell a breakout that works with solderless breadboards: https://www.sparkfun.com/products/13989.
Here's its hookup guide: https://learn.sparkfun.com/tutorials/mi ... okup-guide.

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