9 Replies Latest reply on Mar 27, 2014 8:02 PM by suicidal_orange

    Wolfson could have given us GPIO access


      Wolfson card arrived. Ok so I saw the pictures that the GPIO pins are not accessible with the card fitted - so why did they do this then?

      I've now got to risk de-soldering and replacing the connector on this so far unpowered board. I see no reason why they couldn't put a connector on there to give access to the GPOI - I mean - due to the design now space is not an issue and a few extra pennies to the cost would I'm sure not be an issue. Ok so now to butcher my new board. Bin at the ready.

        • Re: Wolfson could have given us GPIO access

          Because they use most of the GPIO pins to control they card.  Look at the schematic.  The ones they don't use are brought out to the 3 pin header, normally used as a serial port.

            • Re: Wolfson could have given us GPIO access

              Thanks for reply - Yes I've just looked at that right now. Ah well. One day maybe I'll look into using the board but for now another expansion board for the bits and pieces drawer. I really only ordered this from Farnell to bump up the order cost (minimum order price) since I needed a few parts for an audio application I'm putting together for an Arduino. Never mind.

                • Re: Wolfson could have given us GPIO access

                  as mentioned in the GPIO pins thread, the serial pins can be remapped for IO. Runs fine with my app. Of course it only provides 2 IO pins and it is only an option if you don't require the serial port.


                  There are two GPIO labelled pins on the wolfson audio card extension header. Availability as GPIO and driver support is currently unclear. A response by Wolfson would be welcome...


                  Additional GPIO ports might also be added by i2c based extensions, but this will require to somehow get access to the required i2c pins.

                    • Re: Wolfson could have given us GPIO access

                      Yes those I2C pins are the ones I need access to. Maybe I'll get round to changing out that main connector sometime. If I get some time tomorrow I'll try out the card to see how it runs and then then try to add a couple of I2C devices later on. I should have researched the board before just buying it but it was a spur of the moment purchase.

                      • Re: Wolfson could have given us GPIO access

                        Where is The gpio thread to be found ? I only need one relais to shift.

                        i Tried using gpio4 but iT didnt work

                        if you have a link I can use would-be perfect !

                          • Re: Re: Wolfson could have given us GPIO access

                            I was referring to the GPIO thread here in the forum, but the thread does not contain details.


                            Here is a description of the setup I use on a current Raspbian image:


                            The Raspberry Pi serial port is available on the Wolfson audio card at J8, with pins marked RX and TX on the board. The unmarked pin is ground.
                            The wiring can be found in the schematic diagram available on this site on page 8.


                            The mapping to the Raspberry Pi connector and signals is as follows:


                                Wolfson_Card_J8-1:RPI_TX  ->  RPi: P1-08 - TXD0 (ALT0) - GPIO14
                                Wolfson_Card_J8-2:RPI_RX  ->  RPi: P1-10 - RXD0 (ALT0) - GPIO15


                            Details on the Raspberry Pi GPIO connector (called P1) can be found e.g. here:


                            I use the serial ports TX signal pin as an output and the RX signal pin as input.


                            I configure it on startup in /etc/rc.local:



                             # setup GPIO 
                             # enabling pin 15 as input:
                             # exports GPIO pin 15 for use, sets the direction to "in"
                             echo "15" >/sys/class/gpio/export
                             echo "in" >/sys/class/gpio/gpio15/direction
                             # set to active low if required (invert the value)
                             # echo 1 >/sys/class/gpio/gpio15/active_low
                             # input value can be checked by command below
                             # cat /sys/class/gpio/gpio15/value
                             # enabling pin 14 as output:
                             # export GPIO pin 14 for use, sets the direction to output
                             echo "14" >/sys/class/gpio/export
                             echo "out" >/sys/class/gpio/gpio14/direction
                             # set to active low if required (invert the value)
                             echo 1 > /sys/class/gpio/gpio14/active_low
                             # Switch signal to desired value
                             echo 0 > /sys/class/gpio/gpio14/value
                             # or 
                             # echo 1 > /sys/class/gpio/gpio14/value



                            Fortunately, enabling the GPIO pins remaps them back to GPIO from the ALT0 serial port default.


                            In my case the commands in rc.local are only there for initial setup of the pins. They are later controlled by an application. But the rc.local commands contain everything that's needed to use the pins from a shell script.


                            Hope this helps.

                              • Re: Wolfson could have given us GPIO access

                                I'm very much a newbie at Raspberry Pi, but I've succeeded in using the Wolfson DAC's J8 header to hook up a pushbutton switch to execute a system shutdown.

                                What's J7 (the 2 x 8 pin header labelled Ex_Connection for? It seems to have GPIO3, GPIO4 and two GND pins labelled on the schematic.


                                I'm using the Wolfson DAC with a Raspberry Pi as a Squeezebox headphone music player. Oh, and to learn some Raspberry Pi skills.



                      • Re: Wolfson could have given us GPIO access

                        It's a shame the designers didn't use i2c, used anyway and shareable to add controls lines, rather than monopolising the GPIO.

                        Losing SPI_CE0 to a reset function does us no favours. One example application, on this web site, is to add audio to the PiCam. It would be nice to have the option to use an SPI-connected TFT with the WAC in that application. A small graphic display has lots of uses with audio, even for audio servers, where it could show album art. Maybe it can be hacked to use SPI 0 for that.

                        • Re: Wolfson could have given us GPIO access

                          Just commenting to show that I'm also interested in using GPIO alongside the Wolfson card - any explanation of how to access the Ex_Connection would be much appreciated.