Hope this is the correct forum..
We have sporadic communication problems on serial. To test this, I connected two ports of the same card with an null modem cable, set up the interface (4800 8N2, because this is the setting of the device we have trouble with) and send a small binary file (~270KB) with zModem over this.
In this setup I got 1-2 CRC errors per minute - so, the data is corrupted. (This is much more worse then in the 'good old' mailbox time with much faster modems!)
I tested this with three different cards (with different chips: SUNIX, Moschip, Oxford, all PCI-e 1x, no IRQ conflict) and two different cables.
If I connect one end to an USB serial adapter (Asix), there is no problem, also when connecting the two ports on the USB serial adapter.
I can not believe that three different cards are defect. Can anybody give me an hint where to search? (OS: Windows 10)