HDx20 Theory of Operation

Power Supply

There are five voltages present in the player: 5 V, 3.3 V, 2.5 V, 1.5 V and 1.2 V. 5 V comes in from the power connector and is used directly for the USB. 3.3 V is created from 5 V by a switching regulator. Similar regulators are used to create 2.5 V for the DDR SDRAM and 1.2 V for the CPU core voltage. 

Reset

The HD120, HD220, and HD1020 players have a Low Voltage Reset circuit. This circuit will hold the RESET_L signal low until a valid 3.3 V power source is present.

BCM7208 CPU

The HD120, HD220, and HD1020 players utilize a BCM7208 Multimedia CPU. This CPU runs on 3.3 V, 2.5 V, and 1.2 V and runs from a 27 MHz oscillator. The CPU is reset by the RESET_L signal from the low voltage reset circuit going into the RESET_IN pin on the BCM7208. When the RESET_in pin goes from low to high, the BCM7208 will boot from the NAND flash.

Built-in Flash

The boot code in the BCM7208 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 on the flash slots or USB mass storage. 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

The HD120, HD220, and HD1020 players each contain one DDR SDRAM device. When the BCM7208 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 666MHz, with a data rate of 1333MHz.

Serial Port

The player has a built in UART that communicates with the RS-232 level shifter. The MAX232 creates valid RS-232 voltage levels for the transmit pin by using a capacitive voltage switcher.

Video Encoder and Filter

The BCM7208 streams decoded video using a single-data rate clock. It also streams the same video out of the on-board DACs.

Audio Outputs

The HD120, HD220, and HD1020 players each have a single Texas Instruments high quality audio DAC device, which takes in digital audio signals from the BCM7208 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 64 times higher than the AUD_LRCIN. 

The audio output from the TI amplifier is sent directly to the audio output jack. It can drive a 32 Ohm load with a 2 V RMS signal.

On-Board LEDs

There are four on-board LEDs that indicate the following: 

*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 at right.

On-Board Switch

The on-board switch is connected to the GPIO32. A pullup on the button normally sets the GPIO32 to be pulled high. Conversely, the GPIO32 is pulled low when the button is pressed.

Reset Switch/GPIO Button

The on-board switch is connected to the GPIO12. Pressing down the reset button will cause the GPIO12 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/SD Flash Slot

The SDHC/SD flash slot supports SDHC and SD flash cards. 

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 BCM7208.

Ethernet

The 10/100 Base-T Ethernet is implemented on the HD120, HD220, and HD1020 by directly interfacing with the BCM7208. 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 BCM2708 SOC chip. The board utilizes the TPS2065 device, which is over-current protected switch: It can be used to turn the power to the USB device on or off or to detect over-current situations.