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Using 74LVC245 level shifter with Nokia 5100
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Using 74LVC245 level shifter with Nokia 5100

by didymusrex on Sun Jul 07, 2013 6:38 pm

I'm playing around with the Nokia display and am trying to use an SN74LVC245AN as the level shifter. It seems like is should work but I'm not clear what the Vcc (pin 20) and DIR (pin 1) should be connected to (3 or 5v). since it is a bi-directional chip I want to make sure I have 3v on the right side! I've connected the Arduino pins 2-7 to A1-7 on the LVC and B1-7 to the Nokia.

Does anyone have experience working with this chip and the Nokia display? Or is this just total overkill and I should stick with the 4050 that AdaFruit supplies with he display?

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Re: Using 74LVC245 level shifter with Nokia 5100

by adafruit_support_mike on Tue Jul 09, 2013 1:10 am

You do need the level shifter when you connect an Arduino to the 5100 LCD. The LCD driver is a 3.3v chip, and while 5v signals might not kill it immediately, they aren't good for it.

The 74LVC245 only has one VCC pin, and you want to connect that to the 3.3v rail.. again, connecting it to the 5v rail will kill it. The input pins are built to survive voltages up to about 5.5v though, so those can accept input from the Arduino.

The 4050 works the same way, it just has six buffers where the '245 has eight.
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Re: Using 74LVC245 level shifter with Nokia 5100

by guti_haz on Tue Sep 02, 2014 7:21 am

I don't know why I haven't found this post erlier...

I am struggeling with my connection betwenn my arduino and the Xbee (series 2) via a SN74LVC245AN level shifter
the connection works with the xbee adapter kit https://www.adafruit.com/products/126.

I probably connected the wrong voltage (5V) to the Vcc pin on the level shifter...
Hope it's not dead yet, otherwise I should have a replacement.

Could you also explain what the pins Vcc, Dir & OE are used for?
Dir for direction?
According to the function table (attached) - do I have to switch off/on the current for pins OE and Dir, depending on the direction of the dataflow?

In the attached jpg-file you can see my cabeling - I guess I have to change the connection to the Vcc pin on the level shifter to 3,3V, right?
And also wire the OE and Dir pins (is this possible via two digital output pins from the arduino)?

Does it mather, when I'm just using two pins (A1/A2 - B1/B2) - maybe you know if I need more connections for the Xbee?

Best regards!
Attachments
SN74LVC245AN Function Table.jpg
logic level shifter function table
SN74LVC245AN Function Table.jpg (30.11 KiB) Viewed 742 times
Adruino_SN74LVC245AN_Xbee Connection.jpg
my cabeling blueprint
Adruino_SN74LVC245AN_Xbee Connection.jpg (104.59 KiB) Viewed 742 times

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Re: Using 74LVC245 level shifter with Nokia 5100

by guti_haz on Mon Sep 08, 2014 10:51 am

Nobody, who has an advice for me here?

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