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LPC43xx Only able to get 1 SGPIO output working

Question asked by Jonathan Racki on May 9, 2019
Latest reply on May 11, 2019 by Jonathan Racki

I am using an LPC4367JET100 on an LPCXpresso4367 to output data using SGPIO.  Excluding the rest of my project so that I can solely test the SGPIO, I made a simple program that outputs a 32 bit word of alternating bits (0xAAAAAAAA) continuously over SGPIO in order to allow me to test my outputs using a multi-meter.  Since this signal should be equivalent to an average of half the VCC, it should be 1.65v at the pins. 


In the code attached below, SGPIO slice B is outputting to SGPIO pin 8 which corresponds to the P1_12 physical pin.  On this pin, I get the 1.65v output and I can change it too by using different register values, proving that it works.  The problem is the 5 other pins that I need to function do not seem to output this 1.65v (0xAAAAAAAA).  The documentation for SGPIO is very confusing but I believe this is how the pins are muxed internally for 1 bit mode: 


SGPIO slice B  ->  SGPIO pin 8  ->  physical pin P1_12 (SCU function 6 this one works but none of the others seem to)

SGPIO slice L  ->  SGPIO pin 7  ->  physical pin P2_6  (SCU function 0)

SGPIO slice M  ->  SGPIO pin 9  ->  physical pin P1_13  (SCU function 6)

SGPIO slice N  ->  SGPIO pin 11  ->  physical pin P1_4  (SCU function 2)

SGPIO slice O  ->  SGPIO pin 13  ->  physical pin P2_4  (SCU function 0)

SGPIO slice F  ->  SGPIO pin 6  ->  physical pin P2_2  (SCU function 0)


Please correct me if I am wrong on understanding how the SGPIO slices mux internally.  P1_13 is a specific one which did not work where I tried switching the SCU pin function to every possible value and on none did I get any 1.65v output.  I also decided to check all the pins available to me on the board in case I was checking the wrong pins but no other pins had this 1.65v /were controllable via SGPIO slice.

Thank you for looking into this.