Onboard serial port

When Linux starts, an effort is made to detect and configure low-level the serial ports. If the serial ports work OK, there may be no need for you to do any more low-level configuring. If you're having problems with the serial ports, then you may need to do low-level configuring. If you have kernel 2. Starting with kernel 2. It may be just as easy to give each port a unique interrupt if they are available. See Interrupt sharing and Kernels 2.

The low-level configuring setting the IRQ and IO address seems to cause people more trouble than the high-level stuff, although for many it's fully automatic and there is no configuring to be done.

Until the port is enabled and the serial driver knows the correct IRQ and IO address, the port will not usually not work at all. Applications, and utilities such as "setserial" and "scanport" Debian only?? Even if an ISA port can be found by the probing done by the serial driver it may work extremely slow if the IRQ is wrong. See Extremely Slow: Text appears on the screen slowly after long delays. IO address, IRQs, etc. But there are many other types of "resources" so the term has many other meanings.

In summary, the low-level configuring consists of enabling the device, giving it a name ttyS2 for example and putting two values an IRQ number and IO address into two places:. The device driver done by PnP or " setserial " Configuration registers of the serial port hardware itself, done by PnP software or jumpers on legacy hardware.

They are usually correct. But if you're having problems, your serial port may not show up at all or if you do see a message from "setserial" it may not show the true configuration of the hardware and it is not necessarily supposed to. Some PCI serial ports can be automatically detected and low-level configured by the serial driver.

Others may not be. While kernel 2. So you don't need to use "setserial" for it. There is a possible problem if you don't use the device filesystem. PCI ports are not well standardized.

Some use main memory for communication with the PC. Some require special enabling of the IRQ. The output of "lspci -vv" can help determine if one can be supported. This is different than the probing of IO addresses by the serial driver which means reading certain IO addresses to see if what's read looks like there's a serial port at that address.

What the device driver thinks has been set This is what setserial usually sets and shows. What is actually set in the hardware. Both 1. If they're not it spells trouble since the driver has incorrect info on the physical serial port. If the driver has the wrong IO address it will try to send data to a non-existing serial port --or even worse, to some other device. If it has the wrong IRQ the driver will not get interrupt service requests from the serial port, resulting in a very slow or no response.

If it has the wrong model of UART there is also apt to be trouble. To determine if both IO-IRQ pairs are identical you must find out how they are set in both the driver and the hardware. What the driver thinks is not necessarily how the hardware is actually set. If everything works OK then what the driver thinks is likely correct set in the hardware and you don't need to investigate unless you're curious or want to become a guru.

In many cases your ports will automatically get low-level configured at boot-time but not always correctly. To see what is happening, look at the start-up messages on the screen. It's often tricky to freeze them and you may need to hit Ctrl-Alt-Del while Linux is booting to start rebooting and try again.

What these messages display may change as booting progresses and it's often tricky to freeze it at exactly the right words.

Use Shift-PageUp to scroll back to the messages after they have flashed by. Shift-PageDown will scroll in the opposite direction. Here's an example of the start-up messages as of , almost the same as for Note that in older versions ttyS1 was displayed in these messages as ttyS01, etc. Serial driver version 4. Later setserial shows you what was saved in a configuration file which you may edit , but it's not necessarily correct either:. Loading the saved-state of the serial devices Note that the configuration file only had ttyS in it so that ttyS0 and ttyS4 were not affected by it.

In most cases the second message is the correct one. But if you're having trouble, it may be misleading. Before reading the explanation of all of this complexity in the rest of this section, you might just try using your serial port and see if it works OK.

If so it may not be essential to read further. It shows what the device driver thinks is the correct configuration. But this too could be wrong. It just assumes the "standard" ones first message or accepts what is in a configuration file second message.

Neither of these is necessarily correct. If the serial driver has the wrong IRQ, the serial port is very slow or doesn't seem to work at all. If a port shows up here it exists but the IRQ may be wrong. Linux doesn't check IRQs because doing so is not foolproof. If the "COM3" Serial Port you are trying to open is an onboard Serial Port, then the current design of the Serial Communication class does not allow accessing on-board serial ports. In your code above, what is the value of myDevices[0].

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Collectives on Stack Overflow. Learn more. Windows UWP Windows. SerialDevice Not working Ask Question. Asked 6 years, 5 months ago. Active 5 years, 11 months ago. Viewed 13k times. Is it just me, or is this a bug? Here is where I am at for now, but I can't go very far without a serialPort being created AsBuffer ; await serialPort. Partial ; if char rBuffer. ToArray [0]! Append char rBuffer. Improve this question. BernardG BernardG 1, 3 3 gold badges 16 16 silver badges 25 25 bronze badges.

Checking the "official" sample SerialSample found on GitHub, it does the same. This is with The docs are entirely too shoddy to have an informed answer. I'll randomly guess that, since there is no explicit Open method, you can't get one because the device is already in use. Or you forgot to ask for the "serialcommunication" capability in the manifest. Thank you for your answer, Hans. You will need the infrared adapter installed on your motherboard - usually sold separately - to utilize the Infrared feature.

Onboard Parallel Port : This setting lets you decide whether to select parallel port mode resources or disable the parallel port completely. If you have nothing plugged into the parallel port, disabling it will free up valuable system resources. Parallel Port Mode : If you have disabled the parallel port, then this setting is irrelevant.

However, if the parallel port is enabled, you should configure it to run in EPP enhanced parallel port or ECP enhanced capabilities port mode. EPP mode is recommended if the system has just one device, such as a printer, plugged into its parallel port.

Select ECP if you have daisy-chained more than one device - such as an external Zip drive, scanner, printer, or tape drive - to the system's parallel port. To take full advantage of these settings, make sure you're using IEEEcompliant parallel cables.

I recommend the default setting of 3. Onboard Game Port : If you have added a sound card to your system, or if you do not use either MIDI-devices or obsolete joysticks, then this feature should be disabled to free up resources. If, however, you do use the onboard game port, then I recommend the default setting of