CoolRunner II UART controller design


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On 1/19/2021 at 12:14 PM, Snehashis Haldar said:

Could you please let me know what extra hardware I need to implement the RX, TX of the UART?

Go over to Adafruit or Sparkfun. They sell inexpensive TTL USB UART breakout boards or cables. I use these on boards that have a USB UART capability built in. All you need are two spare IO pins; one for TxD and one for RxD. You can connect the cable or breakout board to a PMOD and have a USB UART that your PC can use.

You can probably find a convenient distributor for these things most places in the world if buying from the sources mentioned is a problem. FTDI also sell a cable a a higher cost.

Be mindful of 5V verses 3.3V logic compatibility when using on older devices.

Edited by zygot
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5 hours ago, zygot said:

Go over to Adafruit or Sparkfun. They sell inexpensive TTL USB UART breakout boards or cables. I use these on boards that have a USB UART capability built in. All you need are two spare IO pins; one for TxD and one for RxD. You can connect the cable or breakout board to a PMOD and have a USB UART that your PC can use.

You can probably find a convenient distributor for these things most places in the world if buying from the sources mentioned is a problem. FTDI also sell a cable a a higher cost.

Be mindful of 5V verses 3.3V logic compatibility when using on older devices.

Hi,

Thank You for your reply. I am planning to buy the below.

https://reference.digilentinc.com/reference/pmod/pmodrs232/start

https://reference.digilentinc.com/reference/pmod/pmodusbuart/start

Could you please let me know if these two would be fine for CoolRunner II board?

Thanks in advance.

 

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The RS-232 PMOD is OK if you have a really, really old PC with an RS-232 serial port and DB-9 connector. They haven't made a PC motherboard with those for a long time. Useful baud rates are limited to about 115200 baud. The USBUart PMOD is similar to the TTL USB Uart breakout boards and cables that I referred to. For most Digilent programmable logic boards this is a a fine alternative. The only issue would be that it uses 4 PMOD pins whether you want to or not. The connector is suitable for use with a PMOD. The options that I mentioned just need 2 GPIO pins plus a ground pin so these are more useful for any FPGA board that you will ever use.

So the only question left is the Vccio voltage of the PLD device on the CoolRunner-II. According to the Digilent documentation for your board the PLD has 3.3V IO logic compatibility. So, as long as your PC has a USB 2.0 port available the USBUart PMOD should be fine.

 

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