MattisLind
Veteran Member
More progress! With my digital scope hooked up to the two serial data lines, I can see a lot of variation in tu58em's response time. If it responds within about 20ms, then the VAX seems to be happy and continue (until it fails later; presumably when a response is too slow?). If the response is over about 20ms (as it often is), the VAX appears to time out. From the nature of this behavior, I suspect this is more likely to be device driver screwiness than anything that tu58em is doing. I have the slow-down features of tu58em turned off, and I doubt that it's doing anything screwy by itself. My next step will be to try to resurrect an old Linux laptop that has a real RS-232 port, to get the USB stuff out of the equation. I have a hunch that tu58em may be able to respond faster and more consistently in that environment, and that might lead to success.
I have had problems with turn around time when using FTDI dongles and managed to make it much better after reading this article.