Symphony Link Mode

This article describes how to use Prelude with the evaluation board's module operating in Symphony Link mode.

The first connection

The first time a factory-fresh evaluation-board module is powered up, it defaults to Symphony Link mode, and it begins by listening for Symphony Link gateways that advertise the OPEN Network Token. The firmware embedded in the module controls this process, and it happens regardless whether the evaluation board is attached to Prelude. After the module scans the entire available spectrum, usually 902 to 928 MHz in the US, it connects to the "loudest" available OPEN-network gateway. This process takes between 30 to 60 seconds.

To start controlling the module in Symphony Link mode via Prelude, first setup a Symphony Link gateway, and then Launch Prelude.

The first connection

From Prelude's Connection drop-down menu, select the serial port associated with the evaluation board.  In this example, it is COM21. Click Attach.

You will see Prelude's Status group box begin to update, displaying the status of the evaluation board's module.

Notice that the Application Token displays as NOT Registered, because the factory fresh module has not yet been associated with a valid Application Token. This module is not yet ready to communicate with a Conductor account.

Also notice that the Network Token displays 4f50454e, which is the hex representation of ASCII "Open."  By default, factory-fresh modules advertise the OPEN Network Token. For the module to connect to a Symphony Link gateway, both the module and the gateway must advertise the same Network Token.

Prelude's IRQ Flags section shows that the module has latched several IRQ Flags. Hover over the red dots to investigate which IRQ flags have been set. In the picture below, the four red dots correspond to:

  • IRQ_FLAGS_RESET -- the module experienced a RESET event when it was powered on by connecting to the computer via USB.
  • IRQ_FLAGS_CRYPTO_ESTABLISHED -- the module successfully exchange crypto keys with an in-range Symphony Link gateway.
  • IRQ_FLAGS_CONNECTED -- the module connected to the in-range Symphony Link gateway
  • IRQ_FLAGS_APP_TOKEN_ERROR -- the module is not yet registered with a valid Application Token.

You may optionally clear the IRQ flags by clicking the Clear IRQ Flags button. Doing so will extinguish the IO0 LED on the evaluation board.

Setting the Network Token

From Prelude's Options menu, select Set Symphony Config. Enter the desired Network Token and click OK. Keep in mind that both the module and the gateway must advertise the same Network Token to communicate with one another. For the example pictures that follow, we'll leave the module on the OPEN network with Network Token 4f50454e (which is hex for ASCII "OPEN").

Setting the Network Token

If a new Network Token has been assigned, the module begins searching for a matching gateway. If there is no gateway advertising the same Network Token, the module will set the IRQ_FLAGS_DISCONNECTED flag. If the module does find a matching gateway, it will set IRQ_FLAGS_CONNECTED. One of these states will occur within about 60 seconds.

The Network Token assigned to a module persists in its flash memory.

Setting the Application Token

From Prelude's Options menu, select Set Symphony Config. Enter a valid Application Token from your Conductor account and click OK.

Please refer to the Symphony Link Development Kit Quick Start Guide for instructions to generate a new Application Token. (In this case, we'll set an Application Token from a demonstration Conductor account.)

Setting the Application Token

The module registers with the Conductor account using the provided Application Token.  Prelude's Status panel updates as the registration proceeds.

The module has now successfully connected to an OPEN-network gateway and has registered with a valid Application Token. It is ready to communicate with your Conductor account via a Symphony Link network.

Notice that the module set two new IRQ flags as the Application Token was registered:

  • IRQ_FLAGS_APP_TOKEN_CONFIRMED -- the module registered with a valid Application Token.
  • IRQ_FLAGS_DOWNLINK_REQUEST_ACK -- the module notified Conductor of its current Receive Mode (in this case, the receive mode is OFF).

Once the module is assigned an Application Token, the token will persist in the module's flash memory.

Toggling the Receive Mode

The module operates in one of three receive modes: Off, Always On or Mailbox. To toggle among the modes, select Options > Set Symphony Config. Then select the desired receive mode and click OK.

The module will notify the connected gateway of its new receive mode.

Toggling the Receive Mode

Receive Mode Off

In this mode, the module's receiver is off and the module is not ready to receive a downlink communication from Conductor.

Receive Mode Always On

In this mode, the module's receiver runs continuously and the module is always ready to receive new downlink traffic from Conductor.

Receive Mode Mailbox

In this mode, downlink messages are cached at the gateway. The module must request to receive cached messages from the gateway. In this case, the module's receiver is only energized during the interval required to receive all cached downlink messages. This mode is particularly useful for energy-conscious applications that require downlink.

When Mailbox receive mode is selected, Prelude's Retrieve Mailbox button becomes active. Click on the Retrieve Mailbox button to receive any downlink messages cached by the connected gateway.

Receive Mode Mailbox

Setting the Quality of Service (QoS)

To set the module's Quality of Service (QoS), select Options > Set Symphony Config. Enter the desired Quality of Service and click OK. A valid QoS setting is any integer between 0 and 15, inclusive, with 15 being the highest QoS.

Setting the Quality of Service (QoS)

Select the RF path

The LL-RLP-20 or LL-RXR-27 may be configured for one of two RF paths: (1) through the module's trace antenna; or (2) through the module's on-board coax connector and RF pin. A factory-fresh module defaults to the latter, which directs the RF path to the evaluation board's SMA connector.

To toggle the RF path, select Set RF Path and then select the desired RF path.

Sending uplink messages

Uplink messages are sent using Prelude's Transmit group box. By default, Prelude is configured to transmit messages that are strings of hexadecimal bytes. If desired, plain ASCII-string messages may be sent by de-selecting the Hexadecimal check box. The maximum message-length supported by Symphony Link is 256 bytes.

Also by default, Prelude transmits "acknowledged" uplink messages, meaning the gateway confirms receipt of the uplink message. An "unacknowledged" message can optionally be sent by de-selecting the Acknowledge check box. In this case, the gateway will not confirm receipt of the uplink message and the module will be ready to transmit another message as soon as its transmit queue is empty.

You may optionally configure Prelude to continuously send the same message repeatedly by selecting the Repeat check box.

To send a message, enter the message into the Uplink Message edit box and click Send.

Sending uplink messages

When the Send command is issued, the module will wake up and attempt to reconnect with the gateway with which it was last connected. If the expected gateway is not found, the module will set the IRQ_FLAGS_DISCONNECTED flag, and commence scanning for any available gateways. If the module finds and connects to a new gateway, it will transmit the uplink message. If the module cannot connect to a new gateway, it will set the IRQ_FLAGS_TX_ERROR once the gateway scan is complete.

Acknowledged uplink messages

Prelude triggers an acknowledged transmission when the Acknowledge check box is selected and the Send button is clicked. Once the module receives the message content from Prelude, it attempts to synchronize to the last known gateway. If successful, the module transmits the message and waits for an acknowledgment from the gateway. After the module receives acknowledgment, it sets the IRQ_FLAGS_TX_DONE flag.

If the module does not receive an acknowledgment, it sends the message again up to two more times. After three unsuccessful attempts, the module sets the IRQ_FLAGS_TX_ERROR flag to notify the external host of the send failure.

Unacknowledged uplink messages

Prelude triggers an unacknowledged transmission when the Acknowledge check box is not checked and the Send button is clicked. In this case, the module does not listen for acknowledgment after the message is sent. The module sets the IRQ_FLAGS_TX_DONE after the entire message is sent.


When the Repeat check box is selected and the Send button is clicked, Prelude behaves as described earlier, but with the exception that it will append a single-byte counter to the uplink message. After the module reports either TX_FLAGS_TX_DONE or IRQ_FLAGS_TX_ERROR, Prelude checks whether the Repeat check box is selected. If it is, Prelude increments the counter and triggers another transmission.

Sending a message with the Repeat check box selected automatically causes the Auto Clear check box to become selected. With Auto Clear selected, Prelude periodically clears all IRQ flags.

To stop the repeated transmissions, click Stop.

Viewing uplink messages on Conductor

Uplink messages are sent to the associated Application within your Conductor account. Prelude provides a Conductor UI hyperlink. Clicking on this link opens a web browser directed to the Conductor UI login.

Viewing uplink messages on Conductor

For a quick tutorial to learn how to access your Conductor account and view uplink messages, please refer to the Symphony Link Development Kit Quick Start Guide.

Receiving downlink messages

Downlink messages are triggered from Conductor and addressed to a particular module by referencing the module's universally unique identification number (UUID). To set the module to receive downlink messages, you must first set the Receive Mode to either Always On or Mailbox.

Downlink messages can be sent manually from your account using the Conductor UI, or programmatically using the Conductor APIs.

When Conductor triggers a downlink message, it routes the message to the gateway that is connected to the specified module. The gateway then transmits the message over the air to the module.

  • If the Receive Mode of the module is set to Off, it will not receive the message. Conductor will notify you that the downlink operation failed if acknowledgment was requested with the send command.
  • If the Receive Mode is set to Always On and the module receives the message, the module sets the IRQ_FLAGS_RX_DONE flag. Prelude then retrieves the message from the module and displays the message in the large Receive Window list box. If acknowledgment was requested with the send command, the module will transmit acknowledgment of receipt in the next frame.
  • If the Receive Mode is set to Mailbox, the gateway will cache all downlink messages until the module notifies the gateway it is ready to receive. To retrieve Mailbox messages using Prelude, click the Retrieve Mailbox button located below the Receive Window. Again, if acknowledgment was requested with any pending downlink operations, the module will transmit acknowledgment following receipt.

Logging downlink messages

Prelude can optionally log all downlink traffic to a comma-separated-value (CSV) file. This file includes the message payload, the time-stamp, and the received signal strength associated with each message. The message payloads are logged as both plain ASCII and hexadecimal bytes.

To start logging downlink traffic, specify the desired file name in the Set log file name edit box and then click the Start Logging toggle button.

Logging downlink messages

Shifting to NoMac mode

Prelude can optionally control the evaluation board's module in NoMac mode. To shift to NoMac mode, select Options > NoMac Mode. The Symphony Prelude form will close, and a new NO_MAC Prelude form will open.

Please refer to the NoMac Mode article for more information on using Prelude in NoMac mode.


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