What is a UART in an FPGA? Basics of Serial Ports, COM Port, RS-232, RS-485

Learn the basics of UARTs for use in FPGA. Introduction to baud rates, parity, full vs. half duplex, etc. All important concepts for how you can get your UART in your FPGA up and running. Tutorial for beginners.

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[Aemilindore]

OH my god another video! This is such a lovely topic. So timely for me! I really love your basics videos. You simplify FPGA implementation sio much with giving us code examples. Doing a UART engine in the FPGA is just so great.

[Factory]

I go my Go Board! Excellent practical intro into FPGA concepts. Thanks Russell.

[spacedock]

FYI - Asynchronous does NOT mean that there are no clocks, just that a synchronous clock is not shared between the parties. The clocks are separate and internal to each UART and the start bit is there to align these clocks to the bitstream. Flow control is/was provided to cater for devices such as line printers and teletypes that could not process the data as quickly as it was received due to slow mechanisms and small or non-existent buffers. The flow control allowed the receiver to tell the transmitter to pause until it was ready to process more data.

[sumitkavathekar]

Please do these videos more frequently! We just wait for it

[dave_dennis]

Looking forward to seeing the code behind this! I have a need to implement a UART and was just about to tackle that. It will be much easier to have someone explain me throught it. Thanks!

[boonedockjourneyman]

Great stuff. Hang in there while the Patreon builds.

[plastilinovbly]

Thank you for your content, it is really high quality!

[ninoporcino]

Some time ago I wrote a decoder for a cassette tape format, the old "Kansas City Standard" from the '70s... it's 600 baud, 8 bits, parity even, 2 stop bits. I had to decode it exactly the way you described, looking for the start bit negative edge, the jumping on the middle of the bit for sampling. The stop bit can be any length, not just two stop bits, because the data is asynchrounous. Back to the teletype days when the data was generated from typing on the keyboard.

[sriganeshduraikannu]

Thank for Coming back to youtube. Please make more videos like this. Can you make a video on some complex interfaces like Ethernet, USB or PCIe?

[sumitkavathekar]

That's really great @russel ! Thank you for such videos !

[shri]

That's great video ... pls make such videos each week if possible. can you make a video related to Network On Chip along with different network topologies and its implementation on FPGA....pls

[Monotoba]

7 bits were used on old teletypes and video terminals. A lot of early serial devices also used 7 data bits. If speed counted, the time used to send that one bit at 110 Baud was an issue. Also, the early character encodings also used 7 bits. So only 7 bits were needed for a teletype or similar character-oriented devices. I restored a paper tape reader in the 90s that used 7 bit encoding and 7 bits data at a rate of 300 baud.

[gurkiransb]

You could have typed some word and asked us to guess what it is based on the ASCII values displayed :p

Great video btw. Appreciate your efforts. To the point and simple explanations.
-(I'm just a random person trying to explore more of concepts like FPGA, Logic Gates, etc. and who stumbled upon your channel over a couple of years ago)

[wmhilton-old]

Oh my gosh, I wish I knew/remembered there was a UART on the Go Board! I wrote a whole Go program for a Raspberry Pi to convert USB keyboard events into a SPI and used your SPI Master code to read them lol.

[robertocannella]

Hi, Great Video! Is there a video detailing the coding?

[zeeshanrafique]

please upload a video, which tells that how can we see our fpga output on serial monitor

[tuankietdang]

Thank you for the great videos. I have learnt a lot from your website and youtube channel. I’m gonna graduate in 2020, and in the future I want to be a professional in FPGA. so, what do you think is the best way to learn FPGA professionally? Should I pursuit a master degree?

[ChrisDreher]

Overall good intro to UARTs. Thanks.

One thing to mention: parity comes in several flavors. When someone says that their serial port is set up as "9600, 8N1" the N stands for no parity. Other options include O for odd parity and E for even parity. Some obscure setups even use 1 or 0 parity, which just means that the parity bit is hardcoded to a value or 1 or 0 (not a very useful setting).

[baghdadiabdellatif]

Thank you
Can you send commands ligne with tera term if connected to ms dos pc not to Arduino?

[LLDevLab]

Thank you for great video :) Just couple weeks ago created own UART implementation on FPGA (just for fun). Noticed, that data bits can be 5 – 8 bits. This feels strange for me as well, why someone would send less then 8 bits at once...