raven_squire
Posts: 23
Joined: Fri Jun 29, 2012 8:39 am

Correct buffered line driver IC?

Fri Sep 13, 2013 8:29 am

I have one of the DIY Gertboards and have just assembled it the other day. There were no line driver ICs (MC74HC244AN) in the package. I went to my local electronics store (Jaycar) and they gave me a substitution of SN74HC244N as it was the closest thing that they kept in stock. Is this a suitable substitution? I ask as as I have noticed that sometimes touching the board with the Pi attached will turn the LED's off and on. I also saw this in the manual
""" Depending on the type of 74xx244 buffer chosen, the LED could behave randomly if the port is not
driven properly. In that case it may easily switch state, switching on or off with the smallest of
electronic changes, for example, when the board is simply touched."""

I haven't worked out how to control the Gertboard from the Pi yet so I am not sure if this is an actual problem or just a perceived problem. I would also hate to be pulling my hair out trying to figure out how to get the Pi to control the Gertboard if I had the wrong line driver installed.

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Gert van Loo
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Re: Correct buffered line driver IC?

Sat Sep 14, 2013 8:57 pm

That is a good replacement.
Basically anything with the 244 pinout and capable of running of 3V is acceptable.
I am not sure if this is an actual problem or just a perceived problem.
It is the standard expected behavior.

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Burngate
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Joined: Thu Sep 29, 2011 4:34 pm
Location: Berkshire UK
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Re: Correct buffered line driver IC?

Sun Sep 15, 2013 9:25 am

The HC in the middle means 'high speed cmos' - variations such as F, ALS, HCT, ... refer to the technology and voltage used.
The SN or MC at the start refer to the manufacturer - mainly either Texas or Motorola

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