Following on from an earlier question where the implementation was flawed, can anyone advise if the below is a viable implementation of a circuit to handle a matrix keypad?  The idea is that one keypad column and one GPIO pin (1, 2 or 3) will be 'active' at any one time. This will sequentially flick between the 3 column/pin combinations. The optocoupler will turn on when a keypad button is pressed which will 'activate' (i.e. trigger a change) in GPIO 4.  There would be an optocoupler for each row - I have only included 1 on the diagram to keep it condensed. "in" is the LED anode/cathode and "out" is the photo transistor collector and emitter.  It's a learning exercise on the 555 and 4017, more than anything so any other pointers would be much appreciated.
Is the below a valid circuit implementation and are there any things to watch out for? It's a simplification of the larger circuit but the crux of it is that I need to sink current into two GPIO input pins. The pins are signified by the 1 and 0.  Also, would a diode on the pins be advisable?    Edit: Here's the non-simplified circuit. The question relates to the 3.3v part of it. In essence, the timer and decade counter sequentially pulse current, 'activating' the transistors one at a time. The keypad is a simple matrix keypad. What I'm wondering if I can do is to put a GPIO pin on the line between the keypad and ground. The intended effect is that, when a button on the keypad is pressed, 2 pins will change state - this signifies the row and column.  Note that some of the resistance and capacitance values are notional at the moment.
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Many tries but I still can't make Excel show the sheet bar the way I want (≥ 2 rows), so I'm working with some VBA Scripts kopischke suggested.    FYI, right click on |&lt; &lt;&lt; &gt;&gt; &gt;| button on the bottom-right corner show you a list of up to 15 sheets.  For more, click on View more in the list appeared. Windows License stored in UEFI/BIOS Since Windows 10 (or earlier?). It has become standard to store the license product key in the UEFI/BIOS.  I am in the market for buying a new (custom build, individual parts) PC with a new Windows 10 License.  However I was wondering (and can't find clear information on this subject). What the differences between the licenses are when it comes to OEM and Retail.  If in the far future I were to sell this PC:   Would the license (whether OEM or Retail), be stored in the UEFI/BIOS, where it could be used by the new owner? If so, can I remove the license key from the UEFI/BIOS?   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Even if I remove the "read-only" checkbox, in Properties->Attributes, it automatically comes back again. How do I fix this? Is it a virus that is automatically changing it back to read-only?  regards,  JP Getting an error that a flow "was" activate and cannot be overwritten Number of homomorphisms between two cyclic groups.