cineface

Cineface is a Hardware OSC Controller for the RME Totalmix outputs.

I use the RME Fireface UC USB sound interface studio for 5.1 Surround mixing (for film/cinema audio). It is a great piece of hardware which allows it's users to OSC-control the mixer interface. To for quicker and more reliable work I wanted to create a hardware controller that allows me to see which outputs are currently muted, unmuted, to quickly see what level all of the outputs are set to and to change all of them at once with one dial (as opposed to 6 faders on the TotalMix interface).

Hardware wise I planned to have:

1x Raspberry Pi 3 for all the interfacing
5x LED Buttons (L/R, Center, Lfe, Ls/Rs, Headphones) for muting (green light means active, no light means off)
1x Motor Potentiometer, for global volume control (if I select snapshots from TotalMix it should update)
2x OLED Displays, one for displaying the dB value and one for displaying the current peak levels of the channels

It is meant to run on a raspberry pi 3 and look a bit like this:

Current State of Affairs

^ Working levels display. Note that the Lfe channel is muted. Update rate is surprisingly good.

Raspberry Pi Pinout

Pin	GPIO	Function
6	GND	Buttons/LEDs GND
38	GPIO 20	Button (speakers L/R)
40	GPIO 21	LED (speakers L/R)
8	GPIO 14	Button (center)
10	GPIO 15	LED (center)
12	GPIO 18	Button (Lfe)
11	GPIO 17	LED (Lfe)
16	GPIO 23	Button (rear)
15	GPIO 22	LED (rear)
22	GPIO 25	Button (Headphones)
24	GPIO 24	LED (Headphones)
3	GPIO 2 (I2C1 SDA)	OLED Displays SDA
5	GPIO 3 (I2C1 SCL)	OLED Displays SCL
1	3.3 V	OLED Displays Vcc
39	GND	OLED Displays GND
32	GPIO 12 (PWM)	L293D EN1
?	GPIO ?	L293D IN1
?	GPIO ?	L293D IN2
	GND	L293D GND
21	GPIO 9 (MISO)	MCP3001 ADC Pin 6
23	GPIO 11 (SCLK)	MCP3001 ADC Pin 5
	3.3 V	MCP3001ADC
	GND	MCP3001ADC

Buttons

I use switches with a two-terminal bicolor LED inside (red/green). I am only going to use the green part to display whether a channel is unmuted (green) or muted (off). However one could also use both colors from a raspi as follows (e.g. to indicate clipping):

For the switches I am using the raspi internal pull-up-resistor.

Motor Potentiometer

A motor Potentiometer is a potentiometer coupled to a motor. This means we can read out the current dial position of the potentiometer using an ADC and set the Volume of TotalMix accordingly. Should we change the volume in the TotalMix UI or load up a different snapshot we can use the motor to move the dial into a position where it represents the GUI volume again. This means the motor potentiometer consists of two parts:

1. Driving the motor

Drive motor with H-Bridge (for Simulation see here):

Or use an chip like the L293 see instructions for how to use it with a raspi here (this is what I am going to do, as it takes up less space and I would have had to order P-channel MOSFETs anyways). The principle with the L293 remains the same, it is just less soldering.

2. Reading out the dial

I decided on using a MCP3001 which is a 1-channel 10bit ADC with SPI connector:

Displays

Check out this library which allows you to drive multiple I2C displays from the same pins. For this we have to know the addresses of the displays.

Make sure I2C is enabled in sudo raspi-config

Install i2c-tools:

apt install i2c-tools

Then run i2cdetect -y 1 to get the I2C address of the connected display:

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

Install dependencies so luma.core and luma.oled are happy:

apt install python3-dev libffi-dev libssl-dev python3-pil libjpeg-dev zlib1g-dev libfreetype6-dev liblcms2-dev libopenjp2-7 libtiff5 -y
# and
apt install python3-rpi.gpio python3-pip -y

To speed up I2C edit /boot/config.txt and add:

dtparam=i2c_baudrate=1000000

Address Change

In my case I had to cut the trace for Pin 15 and solder it to Vcc:

Many OLED-Displays have actually resistors/jumpers to change the address, mine didn't. If you have the same issue, look here: ThingPulse/esp8266-oled-ssd1306#138

atoav/cineface