74HCT245 PDF

Remember Me? What's New? Results 1 to 22 of Thread: What is the difference between the 74HCT and sparkfun's logic level converter? What is the difference between the 74HCT and sparkfun's logic level converter?

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As I have already mentioned, it is a good idea to include some kind of feedback mechanism other than sound. We use the speakers as main application namely to play music , but at the same time we want the child to be able to intuitively understand the inner state of our machine by means of light.

From the beginning I wanted the toy to be experienced with another sense, but deliberately excluded any kind of haptic feedback like vibrating for two reasons. My children and their friends already push the device to its limit on a day-to-day basis by sometimes playing a little hard or throwing it around. Actually I am really surprised about what the device is able to take concerning mechanical stress anyways.

That is why I opted for visual feedback. Our Raspberry Pi is restricted not only regarding the number of pins but also their capabilities and the overall computing power. Nevertheless we still want many lights to shine up in different colors and smooth effects while not sacrificing too many pins.

Sturdiness and an easy to use form factor are also important when deciding which product we pick. An LED strip is the first and only thing coming to my mind meeting all of these hardware requirements. Offered by many suppliers they come in almost any length with an RGB LED density of 30, 60 or units per meter all speaking roughly the same protocol.

I think that is also the name of the protocol used to tell the individually addressable pixels which color they should show in what brightness.

Every single light includes a tiny chip reading the data line, understanding the protocol and telling the LED Red, Green and Blue what to do. Just imagine what it means, that CPU manufacturers produce silicon chips working with 7nm transistors.

Another astonishing read is this blog post setting computing periods like a single CPU cycle in relation to comprehensible times. Thinking about space and time always freaks me out distances in the universe, quantum effects, relativity, etc.

Sorry for wandering from the subject. The Raspberry Pi uses a logic level of 3. That means it indicates HIGH with 3. Actually, a lot of electronic devices divide the logic level in three parts and accept LOW to be everything in the lower third of the allowed voltage interval and HIGH to be everything in the upper third.

If I had to guess: I think, the setup would work without a level shifter. The fore-cited LED strips are driven by a single data line and there is a superb library supporting python available completely compliant with our demand. It supports various ways to communicate with the chips inside the LEDs from userland. I probably should have gone with SPI.

The documentation for the device tree overlay states that PWM can only be used if analog audio is disabled. So be sure to either follow along the instructions on how to configure the PCM sound board or disable analog audio yourself. In order to activate that very function, we need to append a dtoverlay to a boot config file. Everything should be ready to tryout the LEDs by using the now compiled test program.

If you see a nice rainbow pattern moving around the LED ring, everything is prepared to go on and use python to talk to the strip. We need to make a few dependencies available before actually building and installing the python API. T herefore we need to run the install step as super user. Afterwards you should be able to test the LED strip part of Marta.


74HCT245 transceiver. Datasheet pdf. Equivalent



74HCT245 DIP


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