CHI035A HighPower Board -keypad

johnc75

New Member
Currently building a project with the CHI035A board driving 2 motors output pairs B4-5 & B6-7. Would like to interface with the picaxe 3 x 4 keypad keypad. The idea is to press a specific 4 digit passkey in order to get the 2 motors to open the "secure compartment doors".
Any thoughts on how to connect the keypad? Thanks:)
 
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oracacle

Senior Member
never used that, but a standard multiplex button attachment would seem to fi the bill, will need 7 pins for that.
4 rows to the reaming port b, 3 columns to input on port c. switch one row high, check port c, then the next row, check port c. constant scan to start with until you get everything nailed down.
 

AllyCat

Senior Member
Hi,

Welcome to the forum.

Or, if you want to minimise the number of PICaxe pins, you can generate an analogue voltage and read it with a READADC on a single pin (and only two wires to the keyboard) by using six resistors. The are various threads on the forum, but this might be good place to start.

Cheers, Alan.
 

hippy

Technical Support
Staff member
Or, if you want to minimise the number of PICaxe pins, you can generate an analogue voltage and read it with a READADC on a single pin (and only two wires to the keyboard) by using six resistors. The are various threads on the forum, but this might be good place to start.
Thanks for reminding us all of that. I had forgotten it was so simply myself. The circuit for those who are intrigued but don't want to dig through the thread is here -

http://www.picaxeforum.co.uk/attachment.php?attachmentid=90&d=1190538769

I would be tempted to increase the ADC pull-down from 10K to 22K to increase the difference between "0" and "#" ADC values but it should work as is.

The disadvantage of an ADC keypad over a genuine digital matrix is it's not so good at handling / ignoring multiple key presses, but that is mitigated by the simplicity of the circuit and ease of use.

Another option is to use IRIN and use a remote as the keypad.
 
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