topic General purpose I/O voltage level problem - Added p/n MC1321x zigbee in 8-bit Microcontrollers

General purpose I/O voltage level problem - Added p/n MC1321x zigbee

bitasobhani — Mon, 13 Oct 2008 20:52:47 GMT

Hi all
I am working on MC1321x zigbee wireless network.
I need more general purpose I/O than what is available on the board.
I used 74LS374 for adding more I/O ports.
The problem is that 74LS374 uses 5Volt Vcc. However its high output voltage is measured about 3.8Volt which is not too larger than 3Volt(high voltage level of the board). Can I connect this 3.8Volt directly to an input general purpose port of the board or I have to convert it to 3Volt. If so, how can I do that?
Thanks alot

Message Edited by NLFSJ on 2008-10-13 12:59 PM

Re: General purpose I/O voltage level problem

bigmac — Tue, 14 Oct 2008 00:28:33 GMT

Hello,

Is there any reason that you can't use a 74HC374 device? This can operate from a 3 volt supply, and so would be compatible with the MC1321x device.

An alternative approach to providing input or output expansion would be to use shift register devices, and to bit bang the SPI communications. For input expansion, a suitable device might be the 74HC589 or 74HC597. Multiple devices may be cascaded.

Regards,

Mac

Message Edited by bigmac on 2008-10-14 03:31 AM