AN-1006: Using the EVAL-ADUSB2EBZ


The EVAL-ADUSB2EBZ features USB-to-I2C and SPI conversion. It is compatible with 1.8 V and 3.3 V target devices and allows for SigmaStudiointegration for most SigmaDSP® processors. Its on-board power regulators are capable of supplying the target board, and it features a standard Aardvark-compatible programming header. The EVAL-UDSUB2EBZ provides SPI control of up to five slave devices with a low profile surfacemount USB miniature Type B connector, and it allows for plugand-play operation.

The EVAL-ADUSB2EBZ is ideal for downloading code and register settings to SigmaDSP processors and codecs with SigmaStudio. It can also be used for real-time tuning of SigmaDSP production units with SigmaStudio.

General Description

The EVAL-ADUSB2EBZ, also known as the USBi, is a standalone communications interface and programmer for SigmaDSPsystems. It translates USB control commands from SigmaStudio to the I2C and SPI communications protocols. The USBi is powered over the USB cable; therefore, no external power supply is required.

The ribbon cable and 10-pin header form a bridge to the target board to connect the communications signals to the target IC. The ribbon cable also carries 5 V power from the USB hub, which can be used to power the target board if desired.

The on-board regulators enable both 1.8 V and 3.3 V IOVDD operation, allowing for increased compatibility with target devices.

Up to five slave devices can be controlled by the USBi simultaneously. To control multiple SPI devices, additional latch signals are provided, although they are not connected to the ribbon cable.

The USBi can be used to control SigmaDSP systems in real time via SigmaStudio, and is capable of programming an EEPROM in self-boot systems. It is an ideal solution for in-circuit programming and tuning of prototype systems.

The USBi only supports USB 2.0 interfaces; the USBi will not work with PCs that only support USB Version 1.0 and USB Version 1.1.

Figure 1.

Using the USB Interface with SigmaStudio

Installing the Drivers

SigmaStudio must be installed to use the USBi. Once SigmaStudio has been properly installed, connect the USBi to an available USB port with the included USB cable. At this point, Windows® XP recognizes the device and prompts the user to install drivers.

Figure 2. Found New Hardware Notification.

Select the Install from a list or specific location (Advanced) option and click Next>.

Figure 3. Found New Hardware Wizard—Installation.

Click Search for the best driver in these locations, then select Include this location in the search. Click Browse to find the SigmaStudio 3.0\USB drivers directory

Figure 4. Windows Found New Hardware Wizard—Search and Installation Options.

When the warning about Windows Logo testing appears on the screen, click Continue Anyway.

Figure 5. Windows Logo Testing Warning.

Adding the USBi to a SigmaStudio Project

To use the USBi in conjunction with SigmaStudio, first select it in the Communication Channels subsection of the toolbox in the Hardware Configuration tab, and add it to the project space.

Figure 6. Adding the USBi Communication Channel.

If SigmaStudio cannot detect the USBi on the USB port of the computer, then the background of the USB label will be red. This may happen when the USBi is not connected or when the drivers are incorrectly installed.

Figure 7. USBi Not Detected by SigmaStudio.

If SigmaStudio detects the USBi on the USB port of the computer, the background of the USB label changes to orange.

Figure 8. USBi Detected by SigmaStudio.

Configuring the USBi to Communicate with an IC

To use the USBi to communicate with the target IC, connect it by click-dragging a wire between the blue pin of the USBi and the green pin of the IC. The corresponding drop-down box of the USBi automatically fills with the default mode and channel for that IC.

Figure 9. Connecting the USBi to an IC.

To change the communication mode and channel, click the drop-down box and select the appropriate mode and channel from the list.

Figure 10. Selecting the Communications Mode and Channel.

Configuring the USBi to Communicate with Multiple ICS

The USBi can communicate with up to five ICs simultaneously. To communicate with more than one IC, add another IC to the project and connect it to the next available pin of the USBi.

Multiple Address Operation with I2C

The USBi can support up to four identical devices on the same bus if the I2C address pins of the target devices are independently set to four different addresses, matching the addresses in the drop-down box in the Hardware Configuration tab of SigmaStudio.

Figure 11. Multiple Address Operation with I2C.

Multiple Address Operation with SPI

The USBi can support up to two identical devices on the same SPI latch if the SPI address pins of the target devices are independently set to two different addresses, matching the addresses in the drop-down box in the Hardware Configuration tab of SigmaStudio.

Figure 12. Multiple Address Operation with SPI.

Multiple Latch Operation with SPI

The USBi can support devices on five different SPI latches. When multiple latches are used, the additional SPI latch signals from the USBi that are not connected to the ribbon cable need to be manually wired to the target.

Figure 13. Multiple Latch Operation with SPI.

The locations of extended SPI latch signals are shown in Figure 14.

Figure 14. Extended SPI Latch Signal Pinout (Bottom View of Board).

Combined Multiple Latch and Multiple Address Operation with SPI

A combination of multiple latch and multiple address schemes can be used, but the total number of devices cannot exceed five.

Controlling the USBi

The USBi has several functions for controlling the target hardware. The control options are accessed in SigmaStudio by right-clicking on the USB Interface in the Hardware Configuration tab.

Figure 15. USBi Control Menu.

Capture Output Data

This option accesses the Capture Window, which displays a log of all communication between the PC and the target IC (see Figure 17).

Device Power On/Off

This option switches the line that supplies power to the target board. By default, the device power is on.

Device Enable/Disable

For supported ICs, selecting this option switches the device to low power mode.

Reset USB Interface

This function performs a software reset of the USB driver, and causes the Cypress USB microcontroller to reload its firmware.

Monitoring the USBi

Using the Capture Window, it is possible to view all outgoing communications transfers from the PC to the target IC. For each write, the write mode, time of write, cell name (if applicable), parameter name, address, value, data (in decimal and hexadecimal), and byte length are shown.

For block writes where more than one memory location is written, only the first location is shown. The expand/collapse button in the leftmost column allows the user to view the full data write.

Using the USBi to Program a Self-Boot EEPROM

After compiling a project, the registers and RAM contents can be written to a target EEPROM for self-boot. To use this functionality, an EEPROM IC must be connected to the USBi in the Hardware Configuration window. After verifying that the EEPROM write protect pin is disabled on the target board, right-click the target IC (SigmaDSP), and select Write Latest Compilation to E2PROM.

Figure 16. Writing to the Self-Boot EEPROM.


The USBi has an EEPROM on the I2C bus at Address 0x51, which it uses to indicate its Vendor ID and Product ID to the PC, as well as boot its internal program. You should avoid having any other EEPROMs in your system design at this address. This EEPROM is not write-protected; therefore, if you attempt to write to Address 0x51, you will overwrite the USBi's onboard EEPROM, and the USBi will cease to function. The USBi cannot be reprogrammed without returning the board to Analog Devices. Most EEPROMs are set to Address 0x51 by setting its pins A0 = 1 and A1 = A2 = 0.

Figure 17. Output Capture Window.

Circuit Schematics

USB Connector

The connection between the host PC and the Cypress USB interface device is via a standard USB cable that carries D+ and D− signals for data communications, a 5 V power supply, and ground. The D+ and D− lines are a one-wire communication interface carried by half-duplex differential signals on a twisted pair. The clock is embedded in the data using the nonreturn-tozero inverted (NRZI) line code. These signal lines connect directly to pins on the Cypress USB interface.

A surface-mounted USB miniature Type B jack was selected for its low profile and increasing ubiquity in consumer electronics.

Figure 18. USB Connector Schematic.

Power Regulator

The Cypress USB Interface I/O ports are capable of operating in both 1.8 V and 3.3 V modes, depending on the target device in the system. Two regulators, one for 5 V to 3.3 V regulation and the other for 5 V to 1.8 V regulation, run simultaneously when the board is powered. A switch (S1) is provided to easily switch the IOVDD supply between the two regulators. LED D4 provides visual feedback that the board is being supplied with 5 V power from the PC USB port.

The position of switch S1 should not be changed when the board is connected to the USB bus.

Figure 19. Power Regulator Schematic.

Cypress USB Interface

The Cypress USB interface is the core of the system, including all of the necessary functionality to convert USB commands into corresponding I2C or SPI read/write transfers, and acts as a FIFO to route data between the host PC and the target device.

Crystal Oscillator Schematic

The Cypress USB interface is its own clock master, and the board includes a crystal oscillator circuit with a 24 MHz piezoelectric crystal resonator to provide stability to the oscillator circuit. The crystal resonator is driven in parallel by the XTALOUT and XTALIN pins of the Cypress USB interface.

Figure 20. Crystal Oscillator Schematic.

Figure 21. Cypress USB Interface Schematic.


The LEDs provide feedback to the user about the status of the Cypress USB microcontroller.

Figure 22. LEDs Schematic.

Table 1. LED Functions
Reference Designator Color Description
D1 Yellow I2C mode is active
D2 Blue GPIO LED, for firmware debug purposes
D3 Yellow SPI mode is active
D4 Red 5 V power being is supplied over the USB bus


The EEPROM is an important system element that identifies the board to the host PC and stores the firmware for the Cypress USB Interface. The EEPROM is programmed during manufacturing via the J2 connector.

Figure 23. EEPROM Schematic

Target Board Power Switch

The USBi is capable of supplying power to the target board after the Cypress USB microcontroller has finished its boot up process. The USB_PWR_ON signal connects to the base of Q2 and turns on both transistors when driven high.

This circuit also enables a software-controlled target reset from SigmaStudio.

Figure 24. Target Power Switch Schematic.

Target Board Programming Header

To properly boot the Cypress USB microcontroller from the EEPROM, it is necessary to remove all other devices from the I2C bus. The ADG721BRMZ analog switch remains open, isolating the I2C bus from the target, until the boot process has completed.

Figure 25. Target Board Programming Header Schematic.

Evaluation Board Schematics and Art Work


Figure 26. Board Schematics Page 1.

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Figure 27. Board Schematics Page 2.

Board Layout

Figure 28. Board Layout—Top View

Figure 29. Board Layout—Bottom View.

Bill of Materials

Table 1. RMS and Log RF Power Detectors
Qty Reference Designator Description Manufacturer Part Number Vendor Vendor Order No.
5 C1, C17, C19 to C21 1.0 μF, 10%, multilayer ceramic, 16 V, X7R (0603) EMK107B7105KA-T
Digi-Key 587-1241-1-ND
9 C2 to C6, C8 to C10, C12  0.10 μF, 10%, multilayer ceramic, 16 V, X7R (0402) ECJ-0EX1C104K Digi-Key PCC13490CT-ND
2 C7, C11 22 pF, 5%, multilayer ceramic, 50 V, NP0 (0402) GRM1555C1H220JZ01D
Digi-Key 490-1283-1-ND
2 C13, C14 10 μF, 20%, SMD tantalum capacitor, 0805, 6.3 V TCP0J106M8R
Digi-Key 511-1447-1-ND
2 C15, C22 15 μF, 20%, SMD tantalum capacitor 0805 6.3 V TCP0J156M8R
Digi-Key 511-1448-1-ND
2 C16, C18 10 nF, 5%, multilayer ceramic, 25 V, NP0 (0603) C1608C0G1E103J Digi-Key 445-2664-1-ND
2 D1, D3 LED, yellow clear, 6.0 mcd, 585 nm, 1206 SML-LX1206YC-TR
Digi-Key 67-1358-1-ND
1 D2 LED, blue clear, 25 mcd, 470 nm, 1206
Digi-Key 67-1701-1-ND
1 D4 LED, red diffused, 6.0 mcd, 635 nm, 1206
 Digi-Key 67-1003-1-ND
1 J1 Header, 10-way, custom ribbon cable, install centered on 14-way footprint
Digi-Key RCC-2184-ND
1 J2 3-way socket, 2 mm, single row, 1 × 3
Digi-Key 2563S-03-ND
1 J3
USB, mini Type B receptacle SMD
Digi-Key WM17116CT-ND
1 Q1
PNP Darlington transistor, SOT223
Digi-Key FZT705CT-ND
1 Q2
NPN general-purpose transistor
4 R1 to R4
10.0 kΩ chip resistor, 1%, 63mW, thick film, 0402
Digi-Key RHM10.0KLCT-ND
2 R5, R12 100 kΩ chip resistor, 1%, 63 mW, thick film, 0402
Digi-Key RHM100KLCT-ND
5 R6 to R10 475 Ω chip resistor, 1%, 63 mW, thick film, 0402
Digi-Key 541-475LCT-ND
1 R11  2.00 kΩ chip resistor, 1%, 63 mW, thick film, 0402 ERJ-2RKF2001X
Digi-Key P2.00KLCT-ND
1 R13
1.50 kΩ chip resistor, 1%, 63 mW, thick film, 0402
Digi-Key P1.50KLCT-ND
1 R14 10.0 kΩ chip resistor, 1%, 63 mW, thick film, 0402 MCR01MZPF1002
Digi-Key RHM10.0KLCT-ND
1 R15
49.9 Ω chip resistor, 1%, 63 mW, thick film, 0402
Digi-Key RHM49.9LCT-ND
1 S1 SPDT slide switch SMD J hook
Digi-Key CAS120JCT-ND
1 TP1 Mini test point white 0.040 inch hole diameter, 0.10 inch × 0.020 inch
Digi-Key 5002K-ND
1 U1 256 kb I2 C, CMOS serial EEPROM 24AA256-I/ST
Digi-Key 24AA256-I/ST-ND
1 U2 CMOS, low voltage, 4 Ω dual SPST switch
Analog Devices ADG721BRMZ
1 U3 USB microcontroller, I2 C (3) 8-bit ports  CY7C68053-56BAXI
Arrow Electronics CY7C68053-56BAXI
3 U4 to U6 Translator, 1-bit, unidirect SC70-5 FXLP34P5X
1 U7 Adjustable, low dropout voltage regulator, 1.0%
ADP1711AUJZ-1.8-R7 Analog Devices ADP1711AUJZ-1.8-R7
 1 U8  Adjustable, low dropout voltage regulator, 1.0%
 Analog Devices ADP1711AUJZ-3.3-R7
1 Y1
Crystal, 24.000 MHz, SMT 18 pF, 3.2 mm × 2.5 mm ABM8-24.000MHZ-B2-T Digi-Key




Brett Gildersleeve