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SwDevAlien
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Contributor

ESXi 6.7 physical serial port stops transmitting after 16 bytes

I am having problems with connecting a proprietary device to an Ubuntu 16.04 installation which is a guest on an ESXi 6.7 host using the physical RS232 port of the motherboard i.e. "Use physical serial port".  The problem can be reproduced by connecting the failing RS232 port using a crossover cable to a PC running Ubuntu 16.04 on "bare metal".  Install minicom on both Ubuntus and then configure them both to use 115200 8E1 (probably irrelevant) then enter 17 characters into the ESXi minicom.  After the 16th character no characters are sent until a character is sent from the non-ESXi minicom.  Characters flow correctly in the other direction.

I have changed my proprietary protocol to send a byte stuffing flag byte to "ESXi" after every 4th character sent from "ESXi" and this works well.

I am reasonably sure that the RS232 ports worked correctly with ESXi 6.5.

This was tested on multiple motherboards using the "embedded" serial port including an Asus P10S-X.  I also tried Ubuntu 14.04.

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