COM port detected a Receive Overrun Error

[Rosita]

I was test COM port TX&RX lookback by Burn-In test V9.0(1016). OS : Windows 10 pro

Every time I test , an error will appear in less than 5 minutes and the following message appears
error message is : COM port detected a Receive Overrun Error
Log Note show: Error at byte 12 of 100

Why does it always error at byte 12? Although there are errors at other bytes, most of them appear at byte 12.




Test settings:
COM port duty cycle :100%
COM port speed : 115200

Our COM port function is normal , but while tested on Burn-In appears error .
We have 2 COM port and the error not only appears while test both port but also appears only test 1 port.

[David (PassMark)]

Are you just running the serial port test by itself?

What kind of test loopback plugs are you using? As overflow is normally the result of poor flow control. Overrun error occurs when new data arrives at the serial port before the previous data has not been read from the UART's receive buffer.

UART = universal asynchronous receiver / transmitter. The UART chip (often built into the SuperIO chip on the motherboard) probably has a 8 or 10 byte buffer. It might be that it takes 12 bytes in the buffer before overflow is detected. You would need to look at the specs for your chip.

This can happen if the system is under very heavy load and can't read the data from the UART quickly enough. But modern CPUs are 1000x of times faster than old serial ports and the system would need to be under extreme load. The lack of flow control (via RTS/CTS) can also aggravate the situation.

[Rosita]

Are you just running the serial port test by itself?
->YES

What kind of test loopback plugs are you using? As overflow is normally the result of poor flow control.
->We use HEADER JUMPER 2 PIN to short TX&RX.

Our UART chip as below.
We have try to reduce the COM port speed and COM port duty cycle , but error still appears.
reference from https://forums.passmark.com/burninte...rrun#post15394

How can I fix the error?

[David (PassMark)]

We use HEADER JUMPER 2 PIN to short TX&RX

So as you haven't connected any of the flow control pins, you probably have no flow control.
No flow control means an increased chance of buffer overflow on the receive side.

We sell proper serial port loopback plugs, which should fix this.

[Rosita]

Our COM port only support TX&RX function. SO even if we don't connected any of the flow control pins that's OK , right?

[Rosita]

What is the difference between send and receive timeout setting to 10ms and the setting to 30000ms? What is the recommended value?
Please give us suggestions about this setting.

[David (PassMark)]

SO even if we don't connected any of the flow control pins that's OK

Clearly it isn't OK, you get overflow errors.
Which means that only some serial port applications can work with your hardware (typically only very low throughput applications).

Send and receive timeout is how long the application will wait for a send or receive request to complete before reporting a timeout error.