Lecture 11 1

Lecture 11: Lab 3 Overview, the ADV7183B Video Decoder and the I2C Bus

ECE 412: Microcomputer Laboratory

Lecture 11 2

Objectives• Introduce Lab 3• Describe the Analog Devices 7183B SDTV video

decoder present on the Digilent VDEC1 board• Discuss the I2C bus that you’ll use to configure the

ADV7183B

Lecture 11 3

Lab 3

FPGA Video Board

VGA Out

SDRAMPowerPCPowerPC

PLB

SDRAMControllerSDRAM

Controller

VGAController

VGAController

ADCController

ADCController

ADC ChipADC Chip

DAC ChipDAC Chip

Frame BufferFrame Buffer

Lecture 11 4

Lab 3• Checkpoint 1: Display static image on VGA

– Software places image in frame buffer, VGA displays

• Checkpoint 2: Video capture, Part 1– Implement YUV->RGB conversion– Display the full motion video stream at 640x480 resolution

• Checkpoint 3: Video capture, Part 2– Implement the portion of the I2C protocol needed to write to

the configuration registers in the ADV7183B video decoder

Lecture 11 5

LAB 3 Overview

Lecture 11 6

New Hardware: Digilent VDEC1

ADV7183B

video analog to digital converter

Lecture 11 7

VDEC1

• The Video Decoder 1 board (VDEC1) with the ADV7183B Video Decoder chip can digitize NTSC, PAL, and SECAM video signals.

• The ADV7183B automatically detects standard analog baseband television signals, and digitizes them with three 54MHz 10-bit ADCs.

• Output data can be sent to an attached system board in 8-bit or 16-bit YCrCb 4:2:2 format.

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ADV7183B•Convert a variety of analog video input formats into 8-bit YUV digital

•Composite (lower quality) and S-Video input (higher quality)

•Supports many modes, including close captioned

Lecture 11 9

I/O Signals• DVDD,AVDD,PVDD,DGND,AGND: Power/ground supplies• AINxx, AGND: Analog video inputs• P[0-15]: Digital video pixel outputs• XTALx: external clock inputs• OE#: Enables the pixel output bus• RESET: Chip internal reset• INTRQ#: interrupt request output• LLCx: Line-locked system clock output• HS, VS, FIELD: Synchronization output signals• SDA, SCLK: Serial clock/data lines for I2C bus

– Used to program/control chip

• ALSB: Jumper selectable I2C address

This material is an overview only; learn to access and use manufacturers datasheets as posted on the ECE412 website.

Lecture 11 10

Connections to XUP Board (1)

Lecture 11 11

Connections to XUP Board (2)

Lecture 11 12

I2C Bus MotivationProblem: Systems in which one or more

microprocessors/microcontrollers control several integrated circuits becoming increasingly common

• Want common control interface to simplify design• Need to limit number of signals required to keep part

costs down• Need flexibility

– Variable number of devices on bus– Support for > 1 master device– Variable data rates

• I2C = Inter-IC Bus

Lecture 11 13

Basic Architecture• Two serial, bidirectional lines connect programming

inputs of all devices• Number of devices on bus limited only by

requirement that total load be < 400pF• Wire interface identical for master and slave devices

SCLK (Serial Clock Line)SDA (Serial Data Line)

Device1

Device2

Device3

Device4

Lecture 11 14

Wired-AND Connection• Pullup resistors pull each line to Vdd when not driven• Any device can drive line by pulling to zero• Devices don’t actively drive to one

– Stop driving and let pullup handle

Lecture 11 15

Implementing this Connection on FPGA• Need to declare SCLK, SDA as inouts• Use tri-state driver to drive each wire

– When you want to drive a zero, enable tri-state and drive a zero

– Otherwise, disable tri-state– Note that this can be accomplished by wiring the data input

of the tri-state driver to zero and generating the appropriate control signals.

Lecture 11 16

Bus Timing • Asynchronous bus – not driven by a constant clock• Base version of bus supports up to 100Kbits/sec data

transfer– Fast version (supported by ADV7183B) allows 400Kbits/sec– “High Speed” version gets up to 3.4 Mbits/sec

• During data transfer, SDA line may only change while SCL line is low– SDA line change while SCL high has special meaning.

Lecture 11 17

Starting and Stopping Transfers• When bus idle, both SDA, SCLK are high• Indicate start and stop of a bus transaction by

transitions on SDA while SCLK high

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Clock Period Determination• Master starts by pulling clock line low

– All devices see this, also pull the clock low, and wait for its required clock low period

– The SCL line will be held LOW by the device with the longest LOW period. Devices with shorter LOW periods enter a HIGH wait-state during this time

• When all devices see clock go high, begin counting off (wait for) its clock high period and pull the SCL line low– SCL goes low when the first device reaches the end of its clock

high period – SCL high period is determined by the shortest clock HIGH period

Lecture 11 19

Arbitration• Bus supports multiple masters, need way to decide which one

wins if multiple try to drive at the same time• Arbitration mechanism: all masters drive bus, when a master

sees the SDA bus having a difference with its own value, it loses and gives up

Lecture 11 20

Sending Data• Byte-oriented interface requires an acknowledgement from

receiver after each byte– Master generates clock pulse for this bit

– Receiver pulls data line low to acknowledge

– Master must abort transfer (with transfer stop) if any byte not acknowledged

• Devices have addresses (8-bit) that they use to determine whether they should pay attention to a bus transfer– Device address typically burned into the hardware

– Can’t have two devices with the same address on a bus• Some devices have one or more programmable address bits to get

around this limitation

• Master sends transfer start, followed by address, followed by a variable number of data bytes.

• Ends transaction with transfer stop

Lecture 11 21

Data Example

Lecture 11 22

Using I2C to Program the ADV7183B• ADV7183B has a large number of control registers

– Select input format – Processing of input image, auto detection, etc.

• Most registers are read-write, some are read-only– As part of initialization, you may need to write all writeable

registers, even those that are reserved– ADV7183B uses a “subaddress” to select these – Easiest way to do this is to build hardware that maps

sequential writes to a PCMCIA memory location onto I2C bus transactions

Lecture 11 23

Writing to ADV7183B Registers

•Address specifies ADV7183B, first data byte gives subaddress (register specifier), second byte is data to be written

Lecture 11 24

Reading From ADV7183B Registers• Uses “combined” format, where a master sends

multiple transfers without a stop bit– First transfer specifies subaddress– Second moves data

Lecture 11 25

ADV7183B Control Registers

• ADV7183B defines 256-byte control register space (00-FF)– Do this with software loop on the IPAQ – FPGA hardware

should just translate PCMCIA I2C– Note that some bytes are read-only (writes to them should

be ignored by hardware)

Lecture 11 26

Control Registers• Several different types

– Analog input type selection– Output type selection– Definition of sync signals– Luminance/chroma control (should be able to create special

effects by adjusting these) – Status outputs – Outputs describing which line is being scanned

• Hint: – ADV7183B Video Decoder manual in the class web– Pages 62-66 define a set of values for the control registers

that auto-detect NTSC input signals and give standard YUV outputs

– Pages 88-89 give some programming examples

Lecture 11 27

Next Time• VGA Video