Brand:

• BSS

Models:

• [List the models affected here on separate lines]

Working with GPIO control

GPIO – Basics (also known as control ports or even sometimes called logic controls since they report logic levels.)

There are 12 inputs and 6 outputs on the control port panel in the center of BSS units.  (the one exception is the BLU-GPX which has considerably more.)

12 Input connections

6 Outputs

These can be set up in 2 or 3-wire mode which we will cover shortly.  By default the configuration is 2-wire mode meaning that inputs or outputs are connected between the appropriate pin specified in the design and one of the two common connections at the bottom on the left.

There are other connections on this but we will cover those in another document.

Project 1 - indicate the status of a Mute with an LED in the real world.

The 6 outputs can each supply 5 volts at 10 milliamps(mA) which is enough to light a simple LED.

In the picture you see a DPST switch. And an LED.  The LED is polarized meaning it only light if the correct voltage is applied it correct direction.  

The port pin supplies the positive voltage and the triangle symbol refers to common ground or one of the two ground connections(either can be used)

The LED comes with one leg longer than the other.  The longer leg is the “Anode" and is where the positive(+) voltage is applied.  So I connected my longer leg to control port output 1 and the shorter leg to my second common ground connector.  The switch I added was connected so that when I close the switch it would connect the control port Input 1 to the first common ground.

Next in Audio Architect I added my DSP to my design and a mono gain that I could use the mute on.

Next I double-click on the mono gain and go to “configure control ports" on the ribbon where I Control-clicked-and dragged the mute button to BOTH control port INPUT 1 and control port OUTPUT 1.

The input will read the state of the switch I connected and the output will change the state of the LED.

Then I go –online and load my design.  Because the mute was off when I went online and the switch was open the mute and the LED stayed off.

If I then flip the switch to the closed state

Project 1 – alternative

Maybe I don't want the light on when the mute is on(no sound) I would rather like to see the light when audio is passing and off when the mute is on, I can do that but I need to use some logic to change the output state.  If I go to the configure LOGIC page and add a long source a NOT gate and a logic end and wire them together as shown I can accomplish this.    The not gate outputs the opposite of what comes in.

If I use a link to link the mute to the logic source I can then assign logic end to the output control port INSTEAD of the mute.

Then I have to go online again and load the changed design.

When I went online the mute was off and the switch is in the open condition so when I looked at the led it was

On(unmuted)

When I close the switch to mute the audio

We see that the led turns off

Topic: 2-Wire Mode

In 2-Wire Mode (This document mainly covers 2-Wire Mode)  the connections are only dependent on a connection to the port and a connection to common ground as you have seen.

Different controls can be connected to inputs.  We have already seen that an external switch can trigger a state change.  But as seen in the drawing here, potentiometers(variable resistors) can also be used to control volumes and resistor ladders can be used to make selections.

Topic: 3 Wire Mode

The main difference between 2-wire mode and 3-wire mode is the third wire which is connected to one of the two R connections and refers to a “reference voltage."   In 2-wire mode there is a reference voltage but it is supplied internally.   In 3-wire mode the reference voltage is supplied by the wiring.  The reference voltage allows some devices more versatility on how they control the design objects.

Note: you cannot wire somethings 2-wire and some things 3-wire.   They must all be of the same type.

Project 2: Fire Mute

Muting audio based on the state of a fire alarm relay.   The fire alarm relay would connect between one of the 12 Control port Inputs and one of the two common ground connections.

Fire alarms come in two main types Normally Open(NO) and Normally Closed(NC)

Normally Open(NO)

In a NO circuit there is no completions of the circuit until the fire alarm relay closes.

Normally Closed(NC)

In a NC circuit there is constant completion of the circuit until the relay opens which effectively breaks the circuit.   This is more common and the advantage to this is that should wiring get damaged you might get a false alarm but you can be confident that as long as wiring is not damaged you know the fire alarm will trigger when the alarm relay opens.

Once the hardware is connected as described, in audio architect you can add a Gain-N object and pass all the outputs through that object.

If you double click on it the gui of the Gain will show that it has a “Master Mute"

If you go to “configure control ports" and hold down the control key on the keyboard you can click and drag this mater mute to the control port you wired your fire mute too.

The mode is important here… if you have a “Normally open" fire relay then the default of “direct action" will be appropriate because it will turn on the mute when the circuit closes.

Of the circuit is “Normally closed" then you will want to select “Direct Action 'inverted'" so that the mute triggers when the Circuit “Opens."

Project 3:  Dry Contact Closure

Without external hardware a true “Dry" contact closure is not possible without external hardware(some sort of relay.)

A relay is made up of two parts.  A coil that when charged will cause a switch to either clos or open depending on the design.

Some relays can operate off of the 5 volts and 10mA or less that is provided from a control port output.

Other relays will work off the 5 volts but require more than 10mA.   An additional roughly 10mA can be obtained by adding multiple control ports wired together.  In the example below this could drive a relay with up to 40mA of current required.  (All ports need to be toggled to the same state when a change in state is made.)

If your relay is NOT a 5 volt relay you can also connect a higher voltage relay using the logic output and an external power supply of the appropriate voltage.  Control port outputs can sink up to 50V DC at 60 mA​​.using the “current sink" wiring approach below:

Whichever method you use to trigger the relay, the following connection would be made to your device requiring the contact closure:

One final caveat for contact closures.   In SOME cases with some devices, a true DRY contact closure is not required… This will vary from device to device but if it is somewhat fault tolerant and can deal with a higher resistance the relay can be dispensed with and a wiring using an external connection like this may work.

(note: this is still subject to the 50 volts and 60mA maximum requirements of a control port output. If a device expects more current to flow or cannot deal with a higher resistance in-between the terminals of the contact closure then a relay is required to get the current to flow!)

Project 3 Alternate

Use of a relay board that recognizes logic levels.   – The biggest advantage here is that many of these board are optically isolated and not limited to 60mA of current draw since the have their own circuitry and power supply.

These boards come in single relay as well as 2x, 4x, 8x and 16x from various manufacturers and with various tolerances.   They recognize the logic “1" and “0" states.  They are pretty common if you go to your preferred online retailer and search on “relay board" you will find many offerings.  Each of these will be a little different but in general they all require external power and that their grounds be tied to the common ground on the DSP.  Typically the size of the relay depends on what you want it to control and how much voltage needs to be controlled.

Generally the BSS DSP is wired to the control board as is indicated below: