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I have 15 output buttons and 4 digital inputs. As in the picture: How do I make each button activate its corresponding address. I have to do this without one button influencing the other. 744ls673, my inputs are already pull-up, the problem is that with this type datashete configuration I can only recognize one key at a time, if I activate keys 1 and 2 at the same time the input will receive 3.
Datasheet MM74C key encoder. You won’t be able to use your common ground switch arrangement but all other potential problems will be solved.
Note that I’m assuming that the inputs rise to a positive voltage if not grounded; i. Add pullup resistors if necessary. If the voltage is negative, then reverse the direction of the diodes.
74ls datasheet & applicatoin notes – Datasheet Archive
You can use a couple of 74LS encoders as shown datashdet their data sheet. There are also purpose built chips that scan the buttons connected as an array like the 74C However your statement “have 74ps673 do this without one button influencing the other” and comments imply you need the ability to detect more than one button pressed at the same time.
That is an entirely different proposition. In that case you would need some form of keypad scanner. Another alternative is to turn your buttons into a rudimentary digital to analog convertor and feed that analog value into whatever analog to digital convertor you may have available.
datasheeh Though datasjeet 16 buttons using that method would be pushing that technique a tad. Since it’s only 74lw673 switches, another way this can be done is to use a shift register rather than an array. That will mean you only need three pins on the micro and a suitable algorithm to manipulate the shift register. Serial in parallel out 74LS Feed one output low through the shift register and read back the status on the common line.
Parallel in serial out 74LS Load from the switches into the shift register all 16 switches attached to 16 pullups, then step feed the word back to the micro. I think I like the latter best since you can grab the complete switch status at one moment in time.
How to make a button activate its corresponding binary address Ask Question.
74LS673 (Big) 16-bit serial-in serial-out shift register
Eduardo Cardoso 1 That’s what diodes are for. Such an arrangement is called a “diode matrix”. This is an area where a microcontroller excels – scanning a keyboard matrix in datashdet case 4×4. Furthermore, a scanned switch matrix is easy to de-bounce. Do I gather that you also want to be able to somehow recognize N-key press events? You are not answering Jonk’s question. You need to define what is to happen when 1 a second key is pressed while the first is held down 2 when the second key is released before the first and 3 when the second key is released after the first.
It sounds as though you need a proper keyboard matrix controller. Internal debounce with single external capacitor. Available output returns to a low level when the entered key is released – even if another is depressed. The Data Available will return high to indicate acceptance of the new key after a normal debounce period. This two-key roll-over is provided between any two switches. You even get to be able to detect SW0 thanks to the Data Available signal!
The most direct way to do it is to build a diode matrix: You forgot the pull-ups though. Yes, I finally have a reason to use the “diagonal diode” symbol adtasheet CircuitLab.
(PDF) 74LS673 Datasheet download
He just wants to “send a ground” to the input signals. I’m assuming the inputs are already pulled high by some means. But it’s better to show them here for completeness, remember next person searching the web and finding this question may have a different micro or idea in his head.
You need to modify your question to clarify that you want to prevent two button pressed simultaneously giving an erroneous code. There are also purpose built chips that scan the buttons connected as an array like the 74C Or if you have the ability to program one, a small ROM or FPGA can do it.
There are other ways dataheet use many diodes. With all of these you would need to handle debounce in code. That looks like Trevor’s “Visio-Lab”. A simple diode arrangement to encode the buttons.
(PDF) 74LS Datasheet PDF Download – BIT SHIFT REGISTERS
Pressing SW1 pulls down IN0 only. Pressing SW2 pulls down IN1 only. Pressing SW4 pulls down IN2. Pull-ups are required, may be internal to micro or not. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name.