topic LPC1114 GPIO connection to TTL in LPCXpresso IDE

LPC1114 GPIO connection to TTL

lpcware — Wed, 15 Jun 2016 22:38:48 GMT

Content originally posted in LPCWare by fi1953 on Wed Apr 13 03:34:08 MST 2011
I wander if I can safely connect any GPIO on the LPC1114 while programmed as Output to a TTL IC input , e.g. the 74HCT04 (to serve as a simple 3.3-to-5 Volt converter).

Re: LPC1114 GPIO connection to TTL

lpcware — Wed, 15 Jun 2016 22:38:49 GMT

Content originally posted in LPCWare by NXP_Europe on Wed Apr 13 04:44:23 MST 2011
hello fi1953,

Connecting to TTL is no problem.

Inputs are 5V tolerant. See for additional info the User Manual on our website.

http://ics.nxp.com/support/documents/microcontrollers/?type=user

Re: LPC1114 GPIO connection to TTL

lpcware — Wed, 15 Jun 2016 22:38:49 GMT

Content originally posted in LPCWare by fi1953 on Wed Apr 13 05:54:03 MST 2011
Thanks for the reply.
I would like to be sure : can I connect a GPIO programmed as Output to a TTL gate input in ANY configuration , or do I have to disable the pull-up and/or pull down option of the GPIO ?

Re: LPC1114 GPIO connection to TTL

lpcware — Wed, 15 Jun 2016 22:38:50 GMT

Content originally posted in LPCWare by serge on Tue Apr 19 06:59:41 MST 2011
Hello all,

Are the I2C pins also 5V tolerant on LPC1343? or did i misread (misinterpreted) the user manual?

Thanks in advance

Re: LPC1114 GPIO connection to TTL

lpcware — Wed, 15 Jun 2016 22:38:50 GMT

Content originally posted in LPCWare by Rob65 on Tue Apr 19 10:08:21 MST 2011
I do remember having read somewhere that the pins are 5V tolerant but rereading the datasheet and manual ... I clearly remember a general statement that most I/O pins are 5V tolerant but can't locate it anymore.

Your big friend is table 7 "static characteristics" in the datasheet (not the user manual) where it is shown that (in digital input mode) Vi = 0..5V.

Please read the notes below the table where it reads "Vdd supply voltage must be present".

Also remember that the hysteresis on the input pins defines low as < 0.3Vdd and high as > 0.7Vdd with Vdd being your 3.3 or 3.6V so I would not stress the I2C timing to the max when using a 5V I2C bus.

Rob

Re: LPC1114 GPIO connection to TTL

lpcware — Wed, 15 Jun 2016 22:38:51 GMT

Content originally posted in LPCWare by NXP_Europe on Tue Apr 19 16:04:37 MST 2011
Hello Serge,

Yes, they are 5 V tolerant.

What kind of I2C (interface) chip is to be connected?

Re: LPC1114 GPIO connection to TTL

lpcware — Wed, 15 Jun 2016 22:38:51 GMT

Content originally posted in LPCWare by yan bellavance on Tue Jul 05 22:47:48 MST 2011

Quote: fi1953
Thanks for the reply.
I would like to be sure : can I connect a GPIO programmed as Output to a TTL gate input in ANY configuration , or do I have to disable the pull-up and/or pull down option of the GPIO ?

I think he is talking about sinking and sourcing IO. the answer to that is it depends how the other port is configured. If one is sourcing then the other should be sinking and vice versa