XDx32 Theory of Operation
This page describes how specific components operate on the XD232, XD1032, and XD1132.
Power Supply
There are seven voltage levels present in the player: 12V, 5V, 3.3V, 2.5V, 1.8V, 1.5V, and 1V.
Reset
BrightSign XDx32 players have a Low Voltage Reset circuit. This circuit will hold the RESET_L signal low until a valid 3.3V power source is present.
BCM7434 CPU
BrightSign XDx32 players utilize a BCM7434 Multimedia CPU. This CPU runs on 3.3V, 2.5V, and 1V and runs from a 27MHz oscillator. The CPU is reset by the RESET_L signal from the low voltage reset circuit going into the RESET_IN pin on the CPU. When the RESET_IN pin goes from low to high, the BCM7434 will boot from the NAND flash.
Built-in Flash
The boot code in the BCM7434 instructs it to continue the boot process by reading additional code from the onboard NAND flash, which can be updated in the field, either from a SDHC/SDXC flash card or a USB mass-storage device. Part of the NAND flash is also used to hold non-volatile parameters. The contents of the boot flash are copied into the SDRAM. The CPU then jumps to the boot code.
SDRAM
BrightSign XDx32 players contain four banks of DDR SDRAM (two 2GB banks and two 4GB banks). When the CPU boots, it will copy the code from the NAND flash device into the SDRAM and then execute the code from the SDRAM. The SDRAM runs at a clock rate of 800MHz, with a data rate of 1600MHz.
Serial Port
The XD1032 and XD1132 have a built in UART that communicates with the RS-232 level shifter. The MAX232 uses a capacitive voltage switcher to create valid RS-232 voltage levels for the transmit pin.
Video Encoder and Filter
The BCM7421 streams decoded video using a single-data rate clock. It also streams the same video out of the on-board DACs.
Audio Outputs
BrightSign XDx32 players each have a single high quality audio DAC device, which takes in digital audio signals from the CPU in an I2S audio format. The AUD_LRCIN is the framing signal for the audio and runs at the frame rate of the audio source (usually either 44.1KHz or 48KHz). The AUD_BITCLK signal is typically 32 times higher than the AUD_LRCIN.
The audio output is fed through an amplifier and sent directly to the audio output jack. It can drive a 32Ω load with a 2V RMS signal.
On-Board LEDs
There are eight on-board LEDs that indicate the following:
LED | Indication |
|---|---|
Green power (Pwr) | Displays when the board is powered up and not in reset mode. |
Green file-system activity (Bsy) | Flashes any time there is file-system activity (on any storage device) |
Green MicroSD activity (µSD) | Displays when a MicroSD card is present. |
Green network activity (Svr) | Displays when the player is connected to the BrightSign Network. |
Green Ethernet activity (Eth) | Flashes when the player is connecting to the network. Displays when connected. |
Green WiFi activity | Flashes when the player is connecting to the wireless network. Displays when connected. |
Yellow update (Upd) | Flashes when the board is being upgraded. |
Red status (Err) | Flashes a certain number of times to indicate which error is occurring. The flash codes are described below. |
| 2: Unspecified error |
| 3: Network recovery script is preparing to run on a device configured for network recovery. |
| 4: No upgrade file found |
| 5: Failed to load kernel module |
| 6: Board is not capable of running the current firmware version. |
| 7: A piece of on-board hardware is not working correctly |
| 8: Problem related to the storage device (either the USB drive or SD card) |
| 9: Problem related to the registry/NAND |
| 10: The autorun script encountered a load/run error. |
| 11: WiFi-related error (mainly, WiFi not found on USB) |
| 12: Unable to find a bootable image |
| 13: The root file system has failed verification, which is used to detect whether the file system has been tampered with. You can recover a player that is showing this error code by performing a firmware update with secure boot. |
| 14: Boot loader failure |
Red/yellow combined | The Update (Upd) and Error (Err) LEDs may flash in unison to indicate that a player cannot connect to the BSN servers during the setup or recovery process. The red and yellow flash codes may also describe an error during the firmware update process as described below: |
| 2: Erase failed |
| 3: Write failed |
| 4: Verify failed |
| 5: Failed to find UBI partition |
| 6: Attempt to write unsigned CFE to unit with secure boot enabled |
| 7: Failed to find UBI partition |
| 8: Failed to create/attach UBI partition |
| 9: Unexpected error |
| 10: Upgrade script exited abnormally |
| 11: Upgrade took longer than expected |
| 12: Update completed but update file could not be deleted |
| 13: Firmware update file could not be read (from firmware v5.1.40) |
On-Board Switch
The on-board switch is connected to the GPIO12, which is pulled low when the service (SVC) button is pressed. Conversely, a pull-up on the button normally sets the GPIO12 to be pulled high.
Reset Switch / GPIO Button
The on-board switch is connected to the reset circuit. Pressing down the reset button will cause the GPIO07 to go low. Holding the reset button low for approximately 10 seconds will cause a hard reset. When the board goes into reset mode, the power LED will be dark until the reset button is released.
SDHC / SDXC and microSD Slots
The XDx32 series has one SDHC/SDXC and one internal MicroSD card slot, both capable of transferring a 25 Mbit/sec video stream, one 5.1 AC3 stream (pass-through), and three stereo PCM tracks simultaneously. There is no inherent limit on the storage capacity of SD cards used for XDx32 players.
NAND Flash
BrightSign players have a built-in NAND flash. All the code for the player is stored on the NAND flash. It may also be possible to store some content on the NAND flash, which is connected directly to the CPU.
Ethernet
The 10/100 Base-T Ethernet is implemented on XDx32 players by directly interfacing with the BCM7434. The player has on-board Ethernet magnetics and termination for the RJ-45 cable.
USB
The USB 2.0 high-speed host controller is implemented internally in the BCM7434 SOC. The board utilizes over-current protected switches that can be used to turn the power to USB devices on or off or to detect over-current situations.