Industrial USB HUB with USB-IF certification

Moxa new USB HUB product line - UPort HUB 404/407 is launched. 

UPort HUB is good USB extenstion solution for industrial environment. If you always have USB compatibility/stability problem such as "Unknown Device", you can take a look at it. It has USB-IF certification with USB 2.0 high speed (480Mbps), including self power and bus power mode. This can eliminate USB compatibility problem. With IEC-61000-4-2 level 4 protection, plug/un-plug frequently will never be a problem and it is very suitable for mobile device manufacturing. For harsh environment, the rugged metal case design, DIN rail mountable and wide range operating temperature support (-40~+85) can fulfil your industrail USB connection requirement. 

http://www.moxa.com/product/UPort_404_407.htm

Win32 DCB Trap

In Win32 serial communication functions, the DCB is very important struct (which is similar to termios struct in *UIX). There are several Win32 functions can change the struct - SetCommState, GetCommState and BuildCommDCB. When you want to use them, you have to notice some traps:

Trap 1:

DCB dcbSerial = {0};

dcbSerial.DCBlength = sizeof(dcbSerial);

dcbSerial.BaudRate = CBR_19200;

dcbSerial.ByteSize = 8;

dcbSerial.StopBits = ONESTOPBIT;

dcbSerial.Parity = NOPARITY;

if(!SetCommState(hSerial, &dcbSerial)){

//error setting serial port state

}

In above code, you clear all fields first and set some basic parameters. Please DON'T set DCB in this way.  That will set zero to important fields such as XonLim and XoffLim and cause some serial adapter driver to return fail. XonLim can not be the same as XoffLim if any flow control is enabled. 

Trap 2:

DCB dcbSerial = {0};

dcbSerial.DCBlength = sizeof(dcbSerial);

BuildCommDCB(“baud=1200 parity=N data=8 stop=1”, &dcbSerial);

if(!SetCommState(hSerial, &dcbSerial)){

//error setting serial port state

}  

This is very similar to trap 1. BuildCommDCB is just for compatbility and only few people will use it in Win32. It use the "mode" (one DOS program) style to describe serial parameter. 

The best way to set DCB is to get previous setting by calling GetCommState. This is also verys similer to *UIX termios - you should get old termios setting before setting new termios. That means: Get all old settings, change the field which you really want to change and set the new settings.

Correct way:

DCB dcbSerial = {0};

dcbSerial.DCBlength = sizeof(dcbSerial);

GetCommDCB(hSerial, &dcbSerial);

dcbSerial.BaudRate = CBR_19200;

dcbSerial.ByteSize = 8;

dcbSerial.StopBits = ONESTOPBIT;

dcbSerial.Parity = NOPARITY;

if(!SetCommState(hSerial, &dcbSerial)){

//error setting serial port state

} 

Change the specific field only and don't touch others if and only if you know what you are doing. This way can keep the previous settings.