Pi + Wolfson + touchscreen LCD ?

Question

I've been trying to find the right combination of parts to make a portable audio recorder with digital in. The wolfson card looks perfect, but I would like to add a touchscreen LCD for start/stop/record/status. I can't seem to find the right combination of parts, and this would be my first real Pi project. Can anyone point me in the right direction? Thanks!

Former Member · Accepted Answer

One of the small TFT touchscreens would be ideal, but the Wolfson card eats up the SPI and all the other GPIO.

Options:

HDMI - easiest to use, but bulky interface to larger screens and not so cheap. (HDMIPI)

DSI - in many ways this is the nicest option, but not available (Due this summer, I think) and not as cheap as small TFTs.

USB - There are some small 'Sys info' TFT USB displays around, but some are very slow to update (50s for a tiny full-screen image!). If you can work with a small set of icons & text it could be OK.E.g. this.

There are some USB monitors around, but could support on Pi be a problem?

SPI - maybe a SPI CS pin can used as a reset by the WAC could be reassigned to an I2C port expander to free one SPI channel. That could enable display on SPI, but not SPI touchscreen. Could be a lot of work.

I2C - a bit slow for image data, but there are some LCD drivers that will work on I2C for (e.g. RA8875, display + 4-wire resistive touchscreen). Multi-drop bus can wire in parallel with WAC, soldering required.

Serial - slow, but pins are available on the WAC.

Former Member · Answer

I have a similar plan to you (I want to record analogue) but have decided that a screen wouldn't be needed on a portable recorder, and in fact it could be bad - screens use battery life and can break.

Instead I'm planning on doing it using just switches and status LEDs and the only issue I can see is that filenames will have to be randomly generated as recording will always start shortly after power on and with no hardware clock or internet the traditional date formatted names might overwrite...

The switches and LEDs will need to be connected to an I2C expander which should work with the Wolfson but as far as I've read no-one's actually done it. I have the parts here and will be testing over the weekend - I'll update this thread with my findings.