Actually you should use the transistor with the AND gate as well.Davros- wrote: ↑Fri Apr 06, 2018 6:03 pmThe appeal of using less GPIO pins is powerful. Especially as I may want to attach buttons, swtiches, etc to the same Pi unit later. I did not realize that I could use all the IR emmitters at once with the AND gate chip though. That is not that important, but it has appeal for sure. Additionally, I did not realize the need for transisters on the demultiplexer chip and it would be nice to avoid soldering those on a bunch of wires.
Yes.Reared your original post and it was very good, giving specific instructions, but I want to make sure I interpretted it correctly due to my lack of knowledge on the subject. If I were to use the 74HC08 chip I would use in total Power (3.3v), Ground, plus 5 other GPIO pins. Is that correct?
Yes. This GPIO will be used in all 4 AND gates.When you say "output GPIO (18) to one input of each AND gate" I believe you mean solder 4 small wires to the wire going into GPIO pin 18, thus only using one GPIO pin to control the four AND gates. Is this correct?
Yes. Think of this chips as electrical versions of boolean logic - just like you have in programming languages. Each 74xx08 chip contains 4 AND gates, so you'll haveWith the 74HC08 I can both control the IR LEDs individually and all at the same time? I realize you described the abilities of this approach but this aspect is important enough that I wanted to read it again to be sure before I commit.
Yes, you can repurpose these as well. In addition to ALTx all the GPIOs (if I'm not mistaken) can be configured as normal GPIOs as well.If the above is correct, then I would still have a bunch of GPIO pins left to use. Super duper embarassed to ask this, but I am not sure if I can use the specific function GPIO pins as general purpose pins. Pins like Physical pin 8 (BCM 14) is a UART pin and Physical pin 19 (BCM pin 10) is a MOSI pin. Can they can be used for general purposes as well? I realize that if the answer is yes some configuration changes to the Pi may be needed in a few cases such as disabling the serial console to use an UART pin.
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