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JSON configuration

The mass storage class USB endpoint is used to pass the needed A2B configuration as a JSON file. To access it, opens the CONFIG.TXT file. Please be aware that JSON configuration is case sensitive. By default, it contains the following configuration:

{
    "Version": "x.xx",
    "Name": "Default",
    "ResetOnNew": "True",
    "A2BRole": "Master",
    "AudioResolution": 16,
    "UsbInputChannels": 2,
    "UsbOutputChannels": 2,
    "RunInProtobufMode": "True",
    "SupplyVoltage": 5000,
    "AudioRouteMatrixDownstream": [
      [1],
      [2],
    ],
    "AudioRouteMatrixUpstream": [
      [1],
      [2],
    ],
    "A2BMasterConfig" : {
      "SlavesOnBus": 1,
      "DnSlots": 8,
      "UpSlots": 8,
      "AutoDiscovery": "False",
      "SlaveConfiguration":[
        {
          "Node": 0,
          "DnSlots": 0,
          "LocalDnSlots": 8,
          "UpSlots": 0,
          "LocalUpSlots": 8,
          "PowerConfig": "High",
          "CableLength": 4,
          "ConfigureTDM": "True",
          "TdmTxLines": 1,
          "TdmRxLines": 1,
          "TDMMode": "TDM8",
          "TDMOptions": ["EARLY", "INV", "ALT"]
        }
      ]
    },
    "A2BSlaveConfig":
    {
      "TdmRxChannels": 1,
      "TdmTxChannels": 1
    }
}

To configure the A2Bridge the following options can be changed.

Version

The version of the JSON configuration. It needs to be compatible with A2Bridge. The user does not need to change it.

Name

The name of the configuration. Users can change it to save the configuration title.

ResetOnNew

This option is used to configure the behavior on new configuration save. If it is set to True the device will be reset on new configuration uploaded.

A2BRole

Option to configure the A2B role. It can be set to one of these options: “Master” or “Slave”

AudioResolution

Audio resolution in bits per sample.

UsbInputChannels

Number of channels that are send to the device from the PC.

UsbOutputChannels

Number of channels that are send to the PC from A2Bridge box.

RunInProtobufMode

If this option is set, A2Bridge will start automatically in protobuf COM port mode.

SupplyVoltage

Voltage in mV requested to supply connected to USB power delivery port. This voltage will be transfered to A2B bus.

AudioRouteMatrixDownstream

Matrix of the channels transmitted to the A2B bus. Each row is an output channel from the USB interface and each element within a row is an A2B output channel to which the corresponding USB channel’s audio will be routed. 

"AudioRouteMatrixDownstream": [
    [A2B Channel, A2B Channel …], - Channel 1 coming from USB
    [A2B Channel, A2B Channel …], - Channel 2 coming from USB
    …
],

As an example we will create the configuration in which there will be 3 USB input channels and 10 A2B output channels. We want to forward 1st USB channel to A2B channels: 1,2,3,4,5,6. 2nd USB channel will be forwarded to 7,8 A2B channels and the last 3rd channels will be forwarded to 9th A2B channel.

"AudioRouteMatrixDownstream": [
    [1, 2, 3, 4, 5, 6], - USB Channel 1 -> A2B Channels 1,2,3,4,5,6
    [7, 8], - USB Channel 2 -> A2B Channels 7,8
    [9] - USB Channel 3 -> A2B Channel 9
]

AudioRouteMatrixUpstream

Matrix of the channels received from A2B bus and transmitted to USB bus. Each row represents A2B channel received from the bus and each element within a row is an USB output channel number.

!!! info Attention:

It works opposite to AudioRouteMatrixDownstream.

A2BMasterConfig

Contains the configuration used when the device is set to “Master” mode.

SlavesOnBus

Number of slaves available on A2B bus.

DnSlots

Number of down slots going out from the device.

UpSlots

Number of the up slots coming to the device.

AutoDiscovery

Setting this flag to true will cause the A2B discovery to be triggered every 500ms as long as the A2Bridge doesn't reach the Normal state (A2B discovery successful)

SlaveConfiguration

Contains the table of the slave configurations. Each slave configuration should contain following properties:

Node

Node number. The order of the node counting from 0

DnSlots

Number of channels forwarded downward.

LocalDnSlots

Number of the slots coming from the upper-node consumed by the current node.

UpSlots

Number of slots forwarded upward.

LocalUpSlots

Number of slots produced by current node. The number of slots send up to the upper node (to master direction) is equal to UpSlots + LocalUpSlots

PowerConfig

Power configuration. Can be set to one of those values: High or Low

CableLength

Length of the cable to the upper node.

ConfigureTDM

If this option is set the slave TDM configuration will be set by A2Bridge. Can be set to False if the node is configured by itself.

TdmTxLines

Number of TDM TX lines coming from the node (from A2B transceiver to the slave µC)

TdmRxLines

Number of TDM RX lines coming to the node (from slave µC to slave A2B transceiver)

TDMMode

TDM mode. Should be set to the one of the following values: TDM2, TDM4, TDM8, TDM12, TDM16, TDM20, TDM24, TDM32. TDMx is a property which describes the number of channels in one TDM frame.

TDMOptions

Additional TDM configuration. This is the table of flags used for TDM communication.

EARLY

SYNC pin changes one cycle before the MSB of data channel 0

ALT

When not set SYNC pin is active for one BCLK cycle at the start of each sampling period, otherwise SYNC is active for 50% of sampling period

image_alt

INV

Invert Sync signal. When set falling edge of sync references the first channel otherwise it is rising edge.

RXBCLKINV

When this flag is set DRX signal is sampled on falling edge of BCLK.

TXBCLKINV

When this flag is set DTX pin is changed on the falling edge of BCLK.

TDMSS

when this flag is set the slaves TDM slot length is 16 bits; 32 bits otherwise

INTERLEAVE

When this option is set, the channels are interleaved between TDM lines.

image_alt

A2BSlaveConfig

contains the following options used when A2BRole set to Slave:

TdmRxChannels

Number of TDM RX channels (from A2B transceiver to slave µC)

TdmTxChannels

Number of TDM TX channels (from slave µC to A2B transceiver)