Problem with 74165 8-bit PARALLEL-TO-SERIAL CONVERTER


I have problem interfacing with the 74165 (not 74HC165). I only get HIGH as an output (11111111).

This is how it is hooked up with the Arduino Uno

I run this code (i have changed the number of registers to 1)

Any ideas?

You show connections to pins 12 and 13 but the codes says it uses 11 and 12.

johnwasser: You show connections to pins 12 and 13 but the codes says it uses 11 and 12.

I've look at my protoboard and it is wired correctly. The mistake is in the schematics.

Its showing all HIGH because the inputs are all high - go measure the voltages on them if you don't believe that statement. Inputs for TTL must be below 0.8V to guarantee being seen as low.

[ To be less cryptic TTL inputs must be pulled low with about 100 ohm or less. 10k isn't going to affect them much. You normally wire low inputs directly to GND and high inputs via a 1k resistor to 5V (this is to protect the inputs should the 5V rail go above 5V, inputs have abs max of 5.5V, yet power supply abs max is 7V ]

74165 is a very different beast to 74HC165 - why are you using it? It consumes about as much power as your microcontroller!

Thank you for being so awesome! It worked.

I'm using 74165s because, those are the only ones I could get my hands on. If i order them online, the delivery to my country is expensive as hell. The power consumption is not an issue for this project, but I'll get the 74HC165 first chance i get.

I have made a blog which is very helpful for connecting 74165 to arduino mega. Circuit and programs were tested in my private lab and hence you can trust it very much. I think, this blog will help you to interface 74165 to arduino.