Note - serialtest now supports testing the asy driver (16550 UART). However, the x86 UART driver does not support internal loopback and synchronous mode. For example, a loopback device may be attached directly to a computers.This is where the Loop-back is useful. The testing requirements/configurations in burnintest are:Often times the most accessible is the Ethernet port. Most of the results will give me error message of “error while sending data to the COM port(s)”.The characters you type will be sent out over the Ethernet connection to the adapter. Type in the Terminal window and press enter. Run Tera Term and open a Telnet connection to the IP address and Port of the serial adapter you are testing.
But we dont have any serial port yet like /dev/ttyUSB.In Advanced Settings the Use FIFO buffers(requires 16550 compatible UART) is checked. PuTTY), you can verify that the test passed if what you type on the keyboard is displayed on the Terminal (although it's not for all characters).The loopback network interface auto lo iface lo inet loopback The primary network interface. They are small RJ-45, DB-25 or DB-9 plugs with no cable.How Serial Port Loopback Test work internally/underneath When doing a Serial Loopback Test on a USB Port (assume COM1) using Hyperterminal or any other serial terminal (i.e. Loopback adapters ship with all Digi Terminal Server products. Does the settings in the COM port in any way affecting the loopback test performed? How does it relate to the default settings in the COM port?3. However the default COM port settings as can be seen above is 9600bps and the receive and transmit buffers are both set to high. The chipset Serial I/O Unit can support up to 115Kbps. The port speed of the BurnInTest was set to 115200kb/s. How does the duty cycle(set to 100) affect the COM port transmission?2. It adds a delay between each Cycle. In summary, I suspect you are getting buffer overrun errors and would use BurnInTest V5.0 to check this:1. Specifically for loopback test, what are the improvements on the v5.0 of the Burn InTest Pro compares to v4.0?(bug fixes, etc)Your clarification on these queries would be much appreciated.I have prepared an initial response. Does the Linux version in any way different than the Windows version? Does it suggest an OS or driver problem?5. We also tried the test using the Linux version of BurnInTest and for boards that have critical error on the loopback test before on BurnInTest for Windows, we did not receive such error now when using the Linux version. Can you please explain how the settings of receive & transmit buffer affect the COM data transmission?4. These Windows settings determine how often the COM port servicing interrupts occurs. You might find if you drop the BurnInTest data rate to 9600 the errors will also not appear.3. We will investigate further tomorrow and respond after this. Loopback Test Serial Port Full Errors AsBurnInTest V5.0 reports framing errors, buffer overrun errors, input buffer overflow errors, parity errors and Transmit buffer full errors as specific error messages (rather than a broader error description that is reported in V4.0). The main benefit with V5.0 for serial port testing is that it reports more specific COM port errors. We will investigate further tomorrow and respond after this.5. I would definitely try V5.0 of BurnInTest as I suspect you have a buffer overrun error.4. The larger the number, the less often the COM ports are serviced, hence it is faster, but the more likely that you will receive overrun errors. Credit card software for macBurnInTest V5.0 will provide a better indication of what the problem is, as we display the Error from the Line Status Register of the UART (such as buffer overruns). BurnInTest sets the baud rate for its serial port usage to that specified by the user in Preferences -> Serial Ports.3. BurnInTest does use the Windows Serial port drivers via the Windows API. Buffer overrun) due to a high setting on the UART FIFO.2. However, I think it is more likely to be an interrupt servicing timing issue (ie. V5.0 of BurnInTest displays samples of the data in level 2 trace files (preferences -> logging), as well as the data in the event of an error. As to why Linux reports differently to Windows for the same hardware, I would have to first suspect that Windows and Linux UART FIFO default settings are different. Please try BurnInTest 5.0 (even just the evaluation version).Continuing on with this point in regards to your Linux question:To answer the Linux question properly I need to know the what the Linux UART FIFO settings are. I suspect this is your problem. A buffer overrun error.In regards to your question re: Duty Cycle, we do not alter the UART clock signal - only add delay between each cycle. And if the interrupt is set to occur after 16 bytes and it is a 16 byte FIFO, then if another byte is received before the interrupt is serviced, you will lose the data, ie. For example the Linux test system may have (by default) the UART FIFO interrupt set to occur when the FIFO has 4 bytes, whereas using the slider in Windows you can change this (e.g. Alternatively, the Linux settings may simply set the Interrupt to occur after the buffer is filled at a different point. At low transfer rates, this is OK. That means, that every time 1 byte is sent or received, the CPU is interrupted. The obsolete 820 UARTs only have a 1 byte buffer. The CPU then moves the received byte out of the UART's buffer and into memory somewhere, or gives the UART another byte to send. For the obsolete dumb UARTS, the CPU gets an interrupt from the serial device every time a byte has been sent or received. The UART itself can't do anything with the data passing thru it, it just receives and sends it. The 16550A (or 16550) FIFO chip comes with 16 byte FIFO buffers. This is called an "overrun" or "overflow".FIFO UARTs help solve this problem. In some cases, the CPU does not get around to servicing the interrupt in time, and the byte is overwritten, because they are coming in so fast. 1, 4 and 8 are other possible choices. Note that the interrupt threshold of FIFO buffers (trigger level) may be set at less than 14. The CPU receives less interrupts, and is free to do other things. This is a significant advantage over the obsolete UARTs, which only had 1 byte buffers. Not only can it wait for more bytes, but the CPU then can transfer all (14 to 16) bytes at a time. Fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,236. Fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,227. While many PC's only have a 16550 with 16-byte buffers, better UARTS have even larger buffers.However I would be fairly sure you could make the change by doing small mod and a quick recompile in your Kernel.Code: static const struct serial8250_config uart_config[] = {188.
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