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Helio board USB and UART serial interface

Honored Contributor II

Hi, I am new to the forum and have been trying to communicate to my Helio board using the USB. 


In the Helio reference manual, it states that the board has an OTG USB PHY (via USB3300-EZK) and a USB-to-UART bridge (via CP2103). I have traditionally used the UART, but I have found it curious that this one uses only 2 pins on the Cyclone V (B19 and C16) -- where as I would normally also use CTS and RTS as control signals. 


Therefore, could someone explain to me what the best option for communicating with the board is and if there is sample Verilog/VHDL code out there for realizing this? 


Thanks a lot, 

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Honored Contributor II

Does anyone know how to use "special function" pins, such as B19 and C16 on Cyclone V SoC? 


These pins are UART_RX and UART_TX, yet I cannot assign them to my signals in the design using the Pin Planner. It gives me the error: "Editing location assignment is not successful. Not assignable.". 


If I dierctly edit the QSF file, I still get the compilation warning: "Some pins have incomplete I/O assignments...".
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