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TerASIC DE3 HSTC -> AD9148

Honored Contributor II

Hi there, basically I am wanting to create my own 'daughter card' for the de3 dev kit (http://www.terasic.com.tw/cgi-bin/page/archive.pl?language=english&categoryno=39&no=260&partno=1) using the Analog Devices ad9148-ebz (http://www.analog.com/en/digital-to-analog-converters/da-converters/ad9148/products/product.html) evaluation board. The connections for the AD9148 are simple and straight forward. There are two 16 bit LVDS data inputs (plus some clock signals). My main concern is with the data signals... 


The DE3 user manual says that each HSTC connector has 60 pair differential channels but 30 are labelled HSTC_RX_n/p[29:0] and the other 30 are labelled HSTC_TX_n/p[29:0]. Am I right in thinking that I only have 30 LVDS signals (per HSTC connector) to transmit data from the FPGA? Are the RX labelled pins solely for receiving data to the FPGA? 


So assuming I want to send 32 bits I would need to use two HSTC connectors OR use single ended connections (120 per connector according to the manual) and selecting the directions myself? Of course if 60 of those single ended connections are limited to RX only then I am in the same situation and still need to use two connectors or look for a different solution all together 


I am a bit stumped with these connectors and any help or advice is appreciated.
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Honored Contributor II

The LVDS signals on the FPGAs are unidirectional only; the IO elements have hard-IP transmit serialize or receive deserialize blocks. Its annoying, I know :) 


If the HSMC connector has only 30 LVDS RX channels, then you would need two HSMC connectors to interface to both 16-bit channels plus their frame clocks. 


However, the data sheets indicates a couple of modes where only one port is required. If those are adequate, then perhaps you only need to interface one of the DAC ports. 


Note that Samtec sells HSMC cables that can be used to connect between boards. I'm not sure what the AD9184 board uses for a connector, but you might be able to just buy a cable to perform the adaptation, or build a simple board with two HSMC connectors, and buy a couple of Samtec cables.