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using seven segment led but want to use pin C7 for adc

 
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brianm



Joined: 08 Mar 2008
Posts: 17

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using seven segment led but want to use pin C7 for adc
PostPosted: Sun Oct 26, 2008 1:45 pm     Reply with quote
Using a 16f690 PIC.


I am using a 4 digit seven segment display to show the readings from 3 adcs but I want to add a fourth and the only pin I have left is pin_c7 which sAN9.

When I write the byte for the number to each digit (c0 thru c7) it of course is touching pin_c7 and monkeying with my ADC reading.

how can I write the desired number to the seven segment but only pass the first 6 bits (0 thru 6) and leave c7 alone so that it can be my 4th ADC.

I could also use C7 to strobe the digits.


An example would be great.

Thanks

Brian
Rohit de Sa



Joined: 09 Nov 2007
Posts: 282
Location: India

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PostPosted: Sun Oct 26, 2008 8:54 pm     Reply with quote
Brian,

Maybe you could tell us a little more about the circuit. That would help. RA4 happens to be AN3, so maybe if that pin is not being used for a critical function, you could shuffle it about. RB4 and RB5 are AN10 and AN11 respectively.

Quote:
When I write the byte for the number to each digit (c0 thru c7)
I agree that byte-wise writing of data is most efficient; but if it is messing with the other functions of the device, you could create a struct which assigns a pin to each bit across different ports. Keep in mind though, that this approach will be much slower, since the controller will be setting/clearing each pin individually. Preferably use fast IO switching (#use fast_io()) in this case and set the TRIS registers accordingly.

Another option is not to use the decimal point on the 7 segment display at all. Connect the seven 'number segment' pins to PORTC. Set AN9 as an analog input, and then just write bytes to PORTC. Nothing will be output on AN9 since it has been declared as an analog input.

Rohit
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