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@[email protected]

I looked at your IP core link. I looks pretty nifty but I have a question. Why in the world would anyone want to put an AXI bus between their logic and an HDL UART? In particular, why would they do that for a soft processor? It seems like hitching a trailer with a couple of mules to the back of your ATV in case you get stuck crossing a creek. Just excess baggage.

Anyway, I'm not sure that an AXI-UART is going to simplify life for anyone needing an HDL UART core. For ZYNQ designs the PS has 2 UARTs. Almost all ZYNQ FPGA platforms connect one of them and the other can be connected to PL pins without an HDL UART instantiation.  It is a nice demo of your AXI work however. I do think that the link might steer people to a useful discussion on the subject of the AXI bus. I'm a bit less sure of posts to this forum that could be viewed as trolling. Perhaps Digilent needs a special AD warning symbol.

RS-232 needs to be designed to work with equipment that might have a significant baud rate error. What's the baud error that your UART tolerates? +/- 15%?

 

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@zygot,

The AXI-lite wrapper is actually just a lite wrapper around a pair of FIFOs and some lighter UART cores.  Indeed, I use those UART cores without AXI all the time.  (Actually, I rarely use AXI myself ... which makes it all the more fun every time someone let's me know that my AXI stuff "just works".)  Not only that, after building the original pair of cores (rxuart.v and txuart.v), I quickly determined that I had very little need of a UART core that supported changing baud rates or anything protocol other than 8N1.  Therefore I have another pair of cores there, rxuartlite.v and txuartlite.v, that are even simpler yet.  These can be subcomponents of the AXI-lite core linked above or indeed used independently, as I often do.  If you don't need AXI, then don't use it.  Your call.  On the other hand, if you are using a Zynq (an unsaid background to this post), then AXI is almost a requirement.

Dan

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6 minutes ago, [email protected] said:

On the other hand, if you are using a Zynq (an unsaid background to this post), then AXI is almost a requirement.

I mentioned ZYNQ because it's not clear what FPGA board the person asking for support is using. You don't need to touch AXI for your ZYNQ designs. I've posted a few alternatives. The Fun with Phasors demo is but one approach.

I use a UART in my designs a lot and have found that I do need a wide range of serial settings. While I don't do much in the way of RS-232 is is still a viable alternative to RS-422 for some applications and it's nice to have a UART that can function in such an environment.

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7 hours ago, Ana-Maria Balas said:

No, I've looked and there isn't an IP for PMOD RS232.

You are probably correct about that. But if you walk over to the desk of one of your compatriots who's been around for a while ( not raising the subject of age ) they will remember the old days when FPGA boards, even those from Digilent, came with one or more RS-232 ports.  This was way before ARM was born but Digilent did provide code for a UART that worked well enough to include in its support. You may have to sit through a few boring discourses but the code is there, somewhere.

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Posted (edited)
13 hours ago, zygot said:

You are probably correct about that. But if you walk over to the desk of one of your compatriots who's been around for a while ( not raising the subject of age ) they will remember the old days when FPGA boards, even those from Digilent, came with one or more RS-232 ports.  This was way before ARM was born but Digilent did provide code for a UART that worked well enough to include in its support. You may have to sit through a few boring discourses but the code is there, somewhere.

Yes, I've already give him the link with some Reference projects which contains also pdf files with documentation for each project, and it explains very well the Uart component which is used with the PmodRS232 (in Interface Reference Component from the Reference projects). The info is there...

https://reference.digilentinc.com/reference/pmod/pmodrs232/start?&_ga=2.200020910.1057145837.1593523143-180711290.1584371590#reference_projects

 

Edited by Ana-Maria Balas

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