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geekhack Projects => Making Stuff Together! => Topic started by: yoobe on Fri, 09 October 2015, 03:48:02

Title: TCA8424 Low-Voltage 8x16 Keyboard Scanner With HID over I2C Compliant
Post by: yoobe on Fri, 09 October 2015, 03:48:02

Hi all,

I just saw this device while searching item for my project.
Did someone used/tested this already? Looks like a cheap chip that could be used in a mechanical keyboard..
I will see if I order one and test it...

Links:
http://www.ti.com/product/TCA8424/description
http://www.ti.com/lit/ds/symlink/tca8424.pdf

Title: Re: TCA8424 Low-Voltage 8x16 Keyboard Scanner With HID over I2C Compliant
Post by: hanya on Fri, 09 October 2015, 03:54:50

I've read the specification of the controller. You need another MCU to connect your keyboard to different kind of interfaces such as USB or PS/2.
Most user designed keyboard is not connected to I2C. It seems recent laptop PC supports such interface internally but there is no connector to be used externally.
[edit] But it looks you are trying to find I2C keyboard, so it would be your choice.

Title: Re: TCA8424 Low-Voltage 8x16 Keyboard Scanner With HID over I2C Compliant
Post by: yoobe on Fri, 09 October 2015, 03:59:15

Yes I was thinking to have a attiny85 or other very small usb device..  Making a PCB with this and a small mcu could be interesting?
At least this will avoid to use all main MCU gpios for the matrix and not have to implement the scan code.

Title: Re: TCA8424 Low-Voltage 8x16 Keyboard Scanner With HID over I2C Compliant
Post by: yoobe on Fri, 09 October 2015, 05:05:04

Another variant: http://www.digilentinc.com/Products/Detail.cfm?Prod=PMOD-IOXP based on adp5589 chip

Title: Re: TCA8424 Low-Voltage 8x16 Keyboard Scanner With HID over I2C Compliant
Post by: ddlawrence on Sun, 11 October 2015, 07:56:44

The TI expander chip is unnecessarily complicated.  This HID spec stuff is forthe birds.  I want a simple keyboard for hacking projects.  The Diligent board with the Analog Devices chip looks much better. 
later............dd

Title: Re: TCA8424 Low-Voltage 8x16 Keyboard Scanner With HID over I2C Compliant
Post by: hanya on Sun, 11 October 2015, 08:49:29

I2C I/O expander used on ErgoDox made many people mad because of its scan speed of the matrix.
If you really need fast scanning of your large matrix, standalone matrix scanner like TCA8424 or another MCU is better for the task.