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Pmod USBUART


KG1242

Question

Hi,

I'm trying to use an ARTY A7, and a Pmod USBUART to communicate to a device that I have, but the specifications weren't exactly clear to me on the Pmod USB/UART. Currently I have my data_out tied to pin 3 on the PMOD Connector which corresponds to TXD. 
 

I also have the Pmod connector attached to Pmod JA. 

1. What should I do with the RTS and CTS lines if I don't plan to use them? 

                -  Also are they required at all to transmit data from the FPGA to the device or vice/versa?

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A quick answer is that you don't care about RTS/CTS as long as the component you are communicating with doesn't use them either. Just ignore them (unless someone from Digilent tells you differently!).

Also, I think you may have the data_out pin connected to the wrong Pmod pin. In my testing with an AXI Uartlite on the Arty, the outbound data is connected to pin 2. So if Tx isn't working on your current configuration, remap it to pin 2.

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Hi @KG1242,

@DerekM is correct that RTS and CTS can be ignored or held low if your software doesn't require it. These signals were needed in older hardware, but not so much anymore.

The UART pins on the Pmod USBUART itself are setup such that RXD (pin 2 on the Pmod) is to receive data from the connected host to the Pmod and TXD (pin 3 on the Pmod) is to transmit data from the Pmod to the connected host. This is explained slightly more the Pmod USBUART Reference Manual, https://reference.digilentinc.com/reference/pmod/pmodusbuart/reference-manual.

Let me know if you have any questions.

Thanks,
JColvin

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