On Board Diagnostic - Audi Infotainment Most (coupe) Audi A5 I

GENERAL INFORMATION

Energy Management

Most control modules, which are needed for the audio system, are connected to the energy management system. This means the MOST-bus switches off if there is a poor energy balance in the vehicle. Depending on the state of the battery, there are different switch-off levels which have an effect on the different control modules. Audio output is not possible after a switch-off level has been activated.

Note. The MOST-bus will continue to run for a certain amount of time with terminal 15 ignition on and without pressing the button on the multimedia control head -E380-. After this time period runs out or depending on the operating condition of the MOST-bus, either a terminal 15 ignition on signal must occur or the ON/OFF button on the multimedia system control head must be operated in order to continue the audio output.

Terminology

BASIC SOUND AMPLIFIER

Note. The numbering of the channels refers only to numerical designations, not the location of the individual channels.

Scheme 4

STANDARD SOUND AMPLIFIER

Note. The numbering of the channels refers only to numerical designations, not the location of the individual channels.

Scheme 5

PREMIUM SOUND AMPLIFIER

Note. The numbering of the channels refers only to numerical designations, not the location of the individual channels.

Scheme 6

MMI 2ND GENERATION COMPONENTS

The audio output in the MOST system has many control modules which are interlinked with individual vehicle systems. These control modules communicate with each other via the different bus versions. The data bus on board diagnostic interface -J533-, which is connected to all the different bus versions, processes the data and sends it to the control module.

Note. AWD vehicles also have rear ABS wheel speed sensors -G44, G46-.

Note. The control modules shown below that are marked with an >>A<< are installed in MMI Basic and replace the front information display control head control module and the front information display control head in the MMI High marked with a >>B<<. In this system, the front information display control head control module is installed at media player position 1. There is also no navigation system with CD drive control module and no radio because these are already part of the front information display control head control module.

Note. The following control modules may be installed in the media player locations: CD Changer -R41- External Audio Source Connection -R199- Mini Disk Player -R153- Front Information Display Control Head Control Module -J523- (only in Basic)

Scheme 7

1. Media Player, Position 1 -R118
2. Media Player, Position 2 -R119
3. Radio -R
4. Navigation System with CD Drive Control Module -J401
5. Front Information Display Control Head Control Module -J523
6. Multimedia Control Head -E380
7. Data Bus On Board Diagnostic Interface -J533
8. Digital Sound System Control Module -J525
9. Inside Microphone -R74

MMI 3RD GENERATION COMPONENTS

The audio output in the MOST system has many control modules which are interlinked with individual vehicle systems. These control modules communicate with each other via the different bus versions. The data bus on board diagnostic interface -J533-, which is connected to all the different bus versions, processes the data and sends it to the control module.

Note. AWD vehicles also have rear ABS wheel speed sensors -G44, G46-.

Note. The Premium Sound System is shown in the illustration. The sound amplifier is integrated with the radio -R- in the Basic or Standard system.

Note. The following control modules may be installed in the media player location. CD Changer -R41- DVD Changer -R161

Scheme 8

1. Media Player, Position 1 -R118
2. Radio -R
3. Information Electronics Control Module 1 -J794
4. Multimedia Control Head -E380
5. Data Bus On Board Diagnostic Interface -J533
6. Digital Sound System Control Module -J525
7. Inside Microphone -R74
8. ABS Control Module -J104
9. Right Front ABS Wheel Speed Sensor -G45
10. Left Front ABS Wheel Speed Sensor -G47
11. 1 - Instrument Cluster/Chassis CAN
12. 2 - MOST-bus

AUDIO PLAY BACK

Note. On the Basic and Standard amplifiers the digital sound system control module -J525- is integrated with the radio -R-.

General Information and Components

The following components are part of the audio play back.

1 - An audio source (for example, a CD changer -R41-, TV tuner -R78- or an external player that is connected via the external audio source connection -R199-)

2 - Digital sound system control module -J525- /radio -R

3 - Speaker

Audio Play Back Functionality

The digital audio signal can be produced by different control modules depending on the vehicle equipment level and the audio source actively selected. For example, if the CD changer -R41- is the selected audio source, then it will read the audio signal coming from the CD. This digital audio signal is sent via the MOST-bus to the digital sound system control module. The digital audio signal is converted, filtered, equalized and amplified into an analog signal inside the digital sound system control module and then sent to the speakers through the individual channels. The type of output to the individual channels depends on the sound setting. The number of channels therefore differs from sound package to sound package.

SOUND SETTINGS

Note. The front information display control head control module -J523- is installed only in vehicles with MMI 2nd Generation. On vehicles with MMI 3rd Generation, this was replaced by the information electronics control module 1 -J794-, which functions as the front information display control head control module.

Note. On the Basic and Standard amplifiers the digital sound system control module -J525- is integrated with the radio -R-.

General Information and Components

The multimedia control head -E380-, the front information display control head control module, and the digital sound system control module are used for the sound settings.

Fader

The fader adjusts the sound between the front and rear speakers. The multimedia control head adjusts the value. The value is evaluated by the front information display control head control module, which is connected with the multimedia control head through a serial interface and sent via the MOST-bus to the digital sound system control module. This sets the ratio between the front and rear channels using the value and then emits either a stronger or a weaker signal. The ratio can be adjusted so that audio output comes only from the front speakers or only from the rear speakers. The fader function is normally available only on vehicles with front and rear speakers. If an adjustment is not possible, then it is due to an incorrect fader setting.

Balance

This feature balances the sound between the right and left sides of the vehicle. The multimedia control head adjusts the value. The value is evaluated by the front information display control head control module, which is connected with the multimedia control head through a serial interface and sent via the MOST-bus to the digital sound system control module. This sets the ration between the right and left channels using the value and then emits either a stronger or a weaker signal. The balance can be adjusted so that sound does not come out of one side at all.

Frequency Correction

Passenger compartments in vehicles do not have optimum acoustics. Passenger compartments with material or leather trim have difference acoustics. The acoustics are stored in a data set so that the speaker signals can be adapted to the vehicle. The digital signal processor will digitally correct the frequency to produce the best possible acoustics inside the passenger compartment. Tone frequencies, which are insulated from the passenger compartment, are amplified.

Surround Level

The digital signal processor will delay the signals in the speaker so as to create a three dimensional sound. When the surround level is set to minimum, then the audio signal is emitted undelayed and in pure stereo. The more the surround level is increased, the stronger the surround effect. This effect is attained in that the output signals from the rear speakers are delayed opposite to the signals from the front speakers. The signal amplification (volume), of the individual speaker signals remains unchanged. This way the surround level has no influence on the fader setting.

The multimedia control head adjusts the surround level. The value is evaluated by the front information display control head control module, which is connected with the multimedia control head through a serial interface and sent via the MOST-bus to the digital sound system control module. The value in the digital sound system control module adapts the channel.

Navigation Audio

The digital signal processor is able to mix the message and the audio source (for example, CD) while the navigation system is giving an instruction. More than 2 values can be selected using the multimedia system control head to set the loudness of the language for the audio source. The values are evaluated by the front information display control head control module, which is connected with the multimedia control head through a serial interface and sent via the MOST-bus to the digital sound system control module. If, for example, the navigation system is going to give a direction, the digital sound system control module will automatically adjust the volume. The audio signal will be lowered so that the direction can be understood. The adjusted volume will be emitted through the different channels while the other sound settings will be maintained. Fader, balance and other settings are not affected.

POSITION-DEPENDANT VOLUME/RUNNING TIME CORRECTION

The evaluators sit inside the vehicle. The digital signal processor makes a correction to the volume and the running time in order to compensate for the different lengths the sound has to travel to the individual speaker. The sound to the individual speakers is either increased or decreased.

Scheme 9

1. Input Signals for All Speakers
2. Digital Signal Processor
3. Speaker 1 Signal Strength
4. Speaker 2 Signal Strength
5. Speaker 3 Signal Strength
6. Speaker 4 Signal Strength

The output via the individual speakers is delayed during the running time correction. That is, the signal is emitted sooner to the speakers that are further from the set position (for example, driver) than to the speakers that are closer to this position.

Scheme 10

1. Input Signals for All Speakers
2. Digital signal processor
3. Speaker 1 Delay (closest)
4. Speaker 2 Delay
5. Speaker 3 Delay
6. Speaker 4 Delay (furthest)

SOURCE VOLUME AUTOMATIC CORRECTION

Different audio sources send different strength input signals to the digital sound system control module -J525-. This is due, for example, to different CDs or radio stations being used. The output volume changes with the different audio sources. The signal strength of the different audio source is controlled by the digital signal processor during the automatic correcting of the source volume so that the customer cannot hear a difference in volume when, for example, switching from listening to the radio to listening to a CD.

Note. On the Basic and Standard amplifiers the digital sound system control module is integrated with the radio -R-.

Scheme 11

1. Audio Source 1 Input Signal
2. Digital Signal Processor
3. Equalized Output Signal
4. Audio Source 2 Input Signal

AUTOMATIC VOLUME CONTROL

General Information and Components

Note. AWD vehicles also have rear ABS wheel speed sensors -G44, G46-.

Note. On the Basic and Standard amplifiers the digital sound system control module -J525- is integrated with the radio -R-.

The ABS control module -J104-, the left front ABS wheel speed sensor -G47-, the right front ABS wheel speed sensor -G45-, the digital sound system control module -J525- and an audio source are part of the speed compensated volume (SCV) function. An interior microphone -R74- is also necessary for the dynamic noise compensation.

Speed Compensated Volume

Depending on the vehicle speed, the volume is increased or decreased. On a FWD vehicle, the ABS control module receives the speed signal from the front ABS wheel speed sensors, evaluates it, and then sends it to the instrument cluster/chassis CAN. On an AWD vehicle, it also receives the signal from the rear ABS wheel speed sensor. The data bus on board diagnostic interface -J533- reads the signal and sends it to the optical MOST-bus.

The signal reaches the digital sound system control module -J525- via the optical bus, which then adapts the volumes based on the value. The volume increases as the vehicle speed increases, or decreases as the vehicle speed decreases. This adaptation is based on how the customer has set the volume, meaning the volume is never lower than the customer's preferred setting.

Dynamic Noise Compensation

Dynamic noise compensation uses the following values in order to control the volume

1. Driving speed
2. Blower speed
3. Noise from a microphone inside the roof module
4. Volume compensation in the MMI

On a FWD vehicle, the ABS control module receives the speed signal from the front ABS wheel speed sensors, evaluates it, and then sends it to the instrument cluster/chassis CAN. On an AWD vehicle, it also receives the signal from the rear ABS wheel speed sensors. The Climatronic control module -J255- sends the information for controlling the fresh air blower -V2- to the comfort CAN. The data bus on board diagnostic interface reads the signal and sends it to the digital sound system control module. Noises are heard by the interior microphone, which is installed inside the roof module and is connected directly to the digital sound system control module. The multimedia control head can then be used to adjust the noise compensation. The front information display control head control module -J523- evaluates the input and then sends it to the digital sound system control module via the optical bus. Using these values, the digital sound system control module then adjusts the volume inside the vehicle. Soft music is made louder as the vehicle speed increases, or loud music will be made softer.