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AD9106, the next requirement for synchronisation is to ensure coincident TRIGGER edges. The layout technique in Figure 5 can also be applied to the TRIGGER PCB traces routed from the digital outputs of a controller to each individual AD9106 device.


USING THE AD9106-ARDZ-EBZ TO EVALUATE MULTICHIP SYNCHRONISATION To evaluate the synchronisation of multiple AD9106 DACs, two AD9106 evaluation boards and an SDP-K1 controller board can be used.


MATERIALS Two AD9106-ARDZ-EBZ boards USB cable for board-to-PC connection SDP-K1


One 12 V wall wart Signal generator Variable length SMA-terminated cables One SMA-terminated T-splitter


Female to female Arduino connector wires


TABLE 1. BOARD-TO-BOARD CONNECTIONS OF SDP-K1 AND TWO AD9106-ARDZ- EBZ BOARDS


Pin No. P2.1 P2.2 P2.3


SDP-K1 Arduino Uno Connectors Pin Functions NC


IO_PWR_SUPPLY MAIN_RESET


P2.4 SDRAM_&_ARDUINO_ PWR_SUPPLY (3.3 V) P2.5 P2.6 P2.7 P5.1 P5.2 P5.3 P5.4 P5.5 P5.6 P5.7 P5.8 P4.1 P4.2 P4.3 P4.4 P4.5 P4.6 P4.7 P4.8 P4.9


+5V_CON GND GND


ARDUINO_GPIOO/RX TX + 1 GPIO2


GPIO3/PWM GPIO4


GPIOS/PWM GPIO6/PWM GPIO7 GPIO8


GPIO9/PWM P4.10 HARDWARE SETUP


Figure 7. Recommended connections of clock inputs and TRIGGER pins for synchronisation.


Before connecting the three boards, configure the two AD9106-ARDZ-EBZ boards such that DAC outputs are connected to the on-board amplifier and the DAC clock is supplied by an external source connected to J10. Refer to Figure 14b in the Eval-AD9106 Wiki User Guide for the proper JP1 and JP2 connections. Also, set up one of the AD9106- ARDZ-EBZ boards such that the CSB pin of the device on board is connected to the alternate GPIO pin (R39 is installed instead of R38). Ensure that the VIO_ADJUST of SDP-K1 is set to 3.3 V.


Then, connect the output of a high frequency waveform generator to a split SMA- terminated T-splitter to which varying lengths of SMA-terminated coaxial cables can be hooked up.


Figure 8. The actual setup. Instrumentation Monthly June 2024


Next, the connections to the clock inputs and TRIGGER pins of each board shown in


GP1010/PWM/CS GPIO11/PWM/MOSI GPIO12/MISO GPIO13/SCK GND AREF SDA SCL


SPI_CSB_DFLT STD_SPI_MISO STD_SPI_MISO STD_SPI_SCK GND


Connected Nets on AD9106-ARDZ-EBZ Board 1


Board 2


IOREF RESET 3.3 V 5 V


GND GND VIN


EN_CVDDX


IOREF RESET 3.3 V 5 V


GND GND VIN


EN_CVDDX SHDN_N_LT3472 SHDN_N_LT3472


TRIGGERB RESETB


TRIGGERB RESETB


SPI_CSB_ALT


STD_SPI_MISO STD_SPI_MISO STD_SPI_SCK GND


Figure 7 should be set up before the rest of the connections in Table 1. Attach Board 1 to the SDP-K1 Arduino Uno ports then place Board 2 at 180° with respect to Board 1 so that the TRIGGER pins of both boards are side to side. This is the shortest connection of TRIG2 to SDP-K1 digital out resulting in TRIG1 and TRIG2 paths being approximately equal. The actual setup with all connections applied is shown in Figure 8. Board-to-board connections are summarised in Table 1.


SOFTWARE


An example source code developed on Mbed open-source software is available. Minimal changes can be made to these source codes described in detail in the wiki page to independently program each device in the two evaluation boards via SPI. Register values, specifically for Example 3 (DDS-generated sine waves with different start delays and


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