Hi Hans,
We are designing and manufacturing Time and Attendance systems since last 12 years.
This is an MCS-51 device, having a Serial Port
RS232 and RS485 (both inbuilt).
A cable runs from this machine to the PC Serial Port. If the cable length is long, then we also sell the RS232~RS485 convertor to our customer.
Reason No.1:
In our country, if we tell our customer that we want to put an add-on card in their PC for communication, then the first thing the customer will do, is throw out the machine out of the window. Because all the PCs are covered under AMC(Anual Maintenance Contract) by PC vendors of our customer, during this period the user of the PC is not supposed to open the PC, let alone insert an add-on card having RS485.

Reason No.2:
Our company management policies do not allow us to open the Customer PC, because due to any reason, if the customer PC goes down (even by a virus) the blame comes to our company, which will create bad realtions with customer, which everybody avoids.

Reason No. 3:
This product is continuously manufactured product and not a study project.

So for the above reasons, we cannot use in-built RS485 cards.


You said:


We have been using and selling RS232~RS485 convertor since our company came into existence (12 years), and it is a sturdy product. I dont see any reason, why I should buy somebody else's Convertor. As it is when we test our products, we also use Convertors from other makes during the testing of the developed product, just to be sure, so that, if incase our customer already has a RS232~RS485 convertor, compatibilty issues do not come up later.

If Microsoft says that it has a function Sleep(100), then it must work properly in all conditions, or atleast it must be mentioned as Errata in documentation.

If you want to discuss the details of RS232~RS485 converter, I will be able to do so in a limited extent only, since this is a public forum, and it is company's property, which I should not be diverting it to anybody. Please understand I a still working in this company.

Bye and many thanks for your reply.

Mr. Kiran V. Sutar.