uart data slow in one direction

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bartgrefte
 
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uart data slow in one direction

Post by bartgrefte »

Recently I got a CH9121 UART to Ethernet module, to test it I hooked the UART-side up to a FTDI Friend. It works, but there's something weird going on.

If I send text (random typing) using the Putty instance that's connected to the FTDI Friend, text appears immediately on the Putty instance that's connected to the ethernet side (virtual comport) of the UART to Ethernet module. If I hold down a key, the character continuously appears on the 2nd Putty instance.

If I send text (random typing) using the Putty instance that's connected to the ethernet side (virtual comport) of the UART to Ethernet module, there's a very noticeable delay for the individual characters to appear on the Putty instance connected to the FTDI Friend. When holding down a key, the characters appear in groups of about 18 characters, then nothing for a second or two, before the next group of about 18 characters appear.

Does anyone happen to know what causes this?

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adafruit_support_bill
 
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Re: uart data slow in one direction

Post by adafruit_support_bill »

Ethernet stacks typically implement 'nagling' which attempts to minimize the network overhead of mostly empty packets by waiting for more data to accumulate before sending. Putty should have an option to disable that,

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bartgrefte
 
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Re: uart data slow in one direction

Post by bartgrefte »

I went through PuTTY's settings, found that the "disable nagle's algorithm" setting has been checked, so it shouldn't nagle.

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adafruit_support_bill
 
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Re: uart data slow in one direction

Post by adafruit_support_bill »

Not sure what else would cause that. A packet sniffer like WireShark would show you the content and timing of packets. From that you could deduce which side was causing the delays.

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