Can I use this circuit to use GPIO to control MUX ?

Question

I want to use a GPIO to control a MUX in DSP. 
 
 My GPIO connects to a hardware switch, when switch to SRC1 , it pulls high , when switch to SRC2, it pulls low. 
 
 Then , I use this curcuit to control MUX in SigmaStudio 4.7. 
 
 The idea is : comapre GPIO input with DC 0 , if greater than DC0, output DC 0 to control MUX. if equal or less than DC0, output DC1 to control MUX. 
 It's seems work on my hardware. 
 But I want to make sure: Is this a stable solution?

Harishgowtham · Accepted Answer

Hello Dave, 
 Please excuse my reply. 
 JYwu, 
 Please try this attached project. I expect it would work as you want. Replace those switches with MP pins once you verified the logic with the switches. I made the MUX to start with index 1 since this logic defaults to output zero that will select the 0th input by default without any MP pin's assertion. So, to select one of the four inputs, MUX's control input pin must be fed with 1,2,3,4 respectively. I filled the 0th index with zero. You can understand that while you test this project. 
 rotary switch.dspproj 
 Please try this and do reply if you have any query. 
 Regards, 
 Harish)

Harishgowtham · Answer

Hello JYwu, 
 Please try this below method and see whether it works. 
 Please give the debounce value as 20ms in the MPx register below. 
 
 Regards, 
 Harish

Harishgowtham · Answer

Hello JYwu, 
 I think there is no need for the ADCD comparator block. If you have 2x1 MUX, then you can directly connect the GPIO (switch) signal to the control input of the MUX like below. If you have more that 2 inputs, then we would have to implement some logic with AUXADC and LUTs. There are a lot of ways and a lot of projects available. 
 
 Kindly do reply if you have further queries. 
 Regards, 
 Harish

JYwu · Answer

Thanks for your quick response. 
 per your another suggestion : " we would have to implement some logic with AUXADC and LUTs" 
 I also need to use 4 segments switch to switch a "4 in 1 out MUX" in this project. 
 4 segments switch is a hardware swith. I use MP10. MP11, MP12, MP13 as input pins and all pull low. 
 If MP10 is switched, it will be pull high to 3.3V, then the "4 in 1 out MUX" in DSP has to switch to SRC1. 
 And MP11 for SRC2, MP12 for SRC3, MP13 for SRC4. 
 Could you please give me more information or reference URL ?

Harishgowtham · Answer

Hello JYwu, 
 If you have planned to select the input by using MP pins, then you don't need to use 4 MP pins for that. Just use a single MP pin with a counter, every time a rising edge is detected here the counter will be incremented by one. The output value goes up to N-1 and comes to 0 again after another trigger. where N is the number that you enter in the counter box. Please find the attached project below. 
 
 input sel gpio.dspproj 
 Regards, 
 Harish

JYwu · Answer

Hi~ Harish: 
 
 This curcuit works. Thank you very much! 
 I have a concern is: when user rotate the switch, there is some transition state that may cause two MP pins at '1' at the same time. 
 This condition is very short, may be only a few milliseconds. 
 Should I add any "ceiling" function after the "adder" to limit the input of MUX below max value "3" ?

JYwu · Answer

Hi Harish: 
 Got it! 
 Quite a smart solution!

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Can I use this circuit to use GPIO to control MUX ?

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