Access to 5 GPIO pins with Wolfson Sound Card

I think your options are:

1. Wire an I2C interfaced GPIO expander to the Pi I2C pins in parallel with the Wolfson card. Maybe PCF8575, or MCP23017.

2. Use a microcontroller on Pi I2C or serial port to handle your I/O. Serial port is accessible at pins on the WAC.

3. Use a USB I/O device

4. Use a different audio device that doesn't monopolise the GPIO.

Useful links:

MCP23017-E/SP - MICROCHIP - IC, IO EXPANDER, 16BIT, I2C, 28DIP | Farnell UK

Raspberry Pi MCP23017 Port Expander Board Kit | RPI-PORTEXP | HobbyTronics

It's a shame Wolfson didn't use something like this to implement the board control functions, leaving the standard GPIO free.

What is it exactly you need to do with the 5 GPIO ?

As pigraham suggested, there are different ways of getting around the Wolfson occupying all GPIO.

In a project I'm working on, I'm doing the following:

* Use the Serial Tx/Rx pins which are made available on the Wolfson card for serial communication with an ATtiny

* Use an Arduino Micro/Leonardo connected via USB as Keyboard emulator in order to pass buttons being pressed to the Pi

Hope this helps

Frederick

Thanks for your reply. Here are use of 5 GPIO pins:

1. Panic Buttion  GPI

2. Buzzer  GPO

3. Fan control GPO

4. Shutdown - GPI

5. Shutdown complete - GPO

I suggest you use a i2c port expander or USB I/O device.

I have a real-time clock module connected to header pins I have soldered onto the Wolfson to connect the i2c. It works and seems to cause no problems with audio.

By soldering two full rows of header pins to the top of the Wolfson you get a stacking connection to support a standard Pi expansion board. As long as any board you add doesn't use GPIO other than the i2c, and doesn't conflict with an i2c address on the Wolfson, it should work.

IMPORTANT check carefully that any card you attach does not use other GPIO lines or you may damage something.

Insert the pin headers into the female connector of your daughter card to maintain proper alignment. Position the pins over the pins on the Wolfson and carefully solder the pins at each end of each header strip. Solder the pins along the edge then remove the daughter card to access the pins on the inner strip. Be careful not to short the pins solder. Be careful when plugging or removing a daughter card.

You could use the HobyTronics expander in this scheme.

I am also interested in using some of the GPIO while using the Wolfson audio card. I have the card working, streaming audio from a server share over the network and it sounds very good. There is an "expansion header" shown on the photograph of the Wolfson audio card in the user documentation. However, there is no pin out for the "expansion header". There is, in the annexe, a table titled "e. Feature header signal assignment" that details the pin out for a 16 pin header. By a process of elimination (There is only one 16 pin header on the board!) I think the "Expansion header" and "Feature Header" are the same thing. If this is right, you have access to two GPIO connections and a range of audio connectors on this header. Just a shame the documentation is not more consistent.

Anyone from Element 14 or Wolfson like to confirm that the Feature and expansion headers are the same thing and that he pin out is correct?

Only two GPIO are available on header pins on the Wolfson card - UART0_TXD (GPIO14) and UART0_RXD (GPIO15).

The Pi I2C does not route to the expansion header on the Wolfson card. If you want to connect a port expander I suggest soldering a 2 x 3 pin header to the top of the wolfson board at the Pin 1 end to make the I2C pins available to expansion boards and jumpers.

I have soldered such a header and attached a RTC module to it. You could attach a gpio expander by jumper wires. Here is a photo showing the soldered header pins and RTC module. The flying leads from the RTC board connect to a GPIO expander.

Also GPIO3 on expansion header is available (connected to GPIO3 of WM5102 and to P1 pin 22 of RPi). I guess it can be used, else they wouldn't expose it on the expansion header.

The P1 i2c is used to control the WM8804 SPDIF chip, but I see no issue in connecting another devices to the bus as suggested.

I am trying to add an RTC to my Pi/Wolfson Audio card combo and was wondering whether your solution is working well? Also, do you have any more photos/instructions on what you did exactly. I am a newbie to the Pi and electronics in general but am looking to get my pi/wolfson unit to record sound to a particular schedule - hence my needing an RTC. My unit won't have access to wifi so I need to add a clock to it. I might end up using a B+ and the Cirrus Logic Audio Card but I think the problem will be similar as I think that card also takes up all of the GPIO pins.