COM ports at legacy ISA (-like) addresses are still available in a plethora of "industrial"/embedded motherboards and computers in various oddball mechanical form factors. And, quite often there are four or even six of them. Sometimes not all are available at coastline DB9 connectors, some may be inside on dual-row headers...
The COM ports are nowadays typically implemented using LPC SuperIO chips, and the SuperIO UART's of today are fairly decent, which historically wasn't always a rule :-) Typically only up to 115200 bps and a 16B FIFO, but no weird quirks, and apparently even IRQ sharing works, with the stock Windows driver - which is slightly surprising, on an ISA work-alike bus. The LPC chips from Nuvoton (ex Winbond), Fintek, SMSC and ITE can contain 2 or 4 or even 6 UART's, and you can have two LPC SuperIO chips in the system. The highest total number of LPC SuperIO UART's that I've seen together on a motherboard was probably 10. The BIOS typically contains a dedicated menu for the SuperIO config, where you can configure the IO addresses and IRQ's for individual ports. It's typically very smooth and trouble-free. If you have just four COM ports, you can typically use higher IRQ's such as 10 and 5 for COM3 and COM4. On a modern motherboard, in a modern OS, most peripherals are on the PCI-e and do not need the legacy ISA IRQ's - except maybe for the disk controller while still in legacy BIOS compatibility mode (no APIC IRQ's, no MSI's). There are also PCI-based and PCIe-based UART's from Exar and Fintek (historically I liked Oxford Semiconductor UART family very much). These PCI(-e) based devices have no problem with IRQ sharing, have 64 to 256 B of FIFO and speeds up to a megabit (or more). Only... not sure how much use they are in DOS ;-) In the industrial PC niche, a machine typically has a COM port or two, capable of RS422/485. The UART's are (almost) the same as for RS232, the difference is just in the level-shifters (line drivers) - though it is a sign of good taste if the motherboard maker uses an LPC SuperIO chip that can drive an RS485 level-shifter by a dedicated signal, basically the "Transmitter Shift Register Empty" made available on a GPIO pin or RTS or some such. The modern BIOS typically has all-around good support for the LPC SuperIO COM ports, announcing them properly via any relevant interfaces to the operating systems (ISAPnP, ACPI, DMI...) Thus, Windows or Linux typically just report all the onboard COM ports without any extra effort required. Apologies for getting off topic :-) Frank > Typically, that is the correct address for com1. Com 2 is IRQ 3, and > 2F8. Com 3 and 4 if they are supported by the bios are 3E8, and 2E8 > generally. > > I've unfortunately never had a dos machine with all 4 com ports active. > I've used com 3 or 4 periodically with an additional com card, but it > didn't have both com ports on it, and I never had a motherboard that > supported all 4 com ports, but the address 2E0 is not typically > associated with a com port, neither are the various IRQs listed in the > snippet below. Normally the com ports are on com 3 and 4, though I > think it was possible to switch irqs for com3 and com4 to be on > different irqs, in case you wanted to use multiple com ports at the same > time. > > (multiple being more than 2 at a time in this case). > > Part of it may depend on the software you're using to access the com > port as well. The driver should handle the translation to/from irqs and > port addresses, so you may not need to worry about that, but you do need > to know what to talk to on your end of the connection to make it all work. > > I've only used screens like you're describing on SBC (single board > computers) like the propeller board from parallax, so I can't offer > anything else to point you in a direction for troubleshooting other than > what I've offered above. Perhaps something here will make a connection > and you'll be able to solve it. > > > > On 3/17/2024 5:10 PM, Thomas Cornelius Desi via Freedos-user wrote: > > For some experimental reasons I got a 19« 3M Touchscreen for the RS-232 > > Port. > > (I attached the VGA cable and the RS-232 cable on both sides) > > (The monitor is functional as a monitor-only. Seller tells me touch > > function is working…) > > > > > > > > My question is about the RS-232 COM1 port. > > > > The AMBIOS (my BIOS on the machine) says that the COM1 port address is > > > > 3F8h/COM1 Enable onBoard Serial port 1 and address is 3F8h. > > > > > > > > > > - I am installing from a USB Stick (= c:\) (=source drive?) > > - port address I wrote: 3F8 > > - interrupt Number: 4 (??? no clue) > > > > The DOS driver directory the seller sent me contains some installation info, > > the examples given differ much from what I set and - of course it does NOT > > work. > > > > Any ideas someone around? > > > > Much appreciated, > > regards, Thomas > > > > > > ================driver info=================== > > > > DOS Only Installation: > > > > From the installation drive type: > > > > INSTALL k: /Axxx /Inn > > > > k source drive > > xxx port address: 2E0, 320 or 330 > > nn interrupt number: 9, 10, 11, 12 or 15 > > > > The software is copied to > > > > c:\mts\touch > > > > You will see that the installation program tries to connect to the touch > > controller by varying COM port speed and parity and, if found, sets the > > line parameters to > > > > 2400 baud > > 8 data bits > > 1 stop bit > > no parity > > ========================================= > > > > > > > > _______________________________________________ > > Freedos-user mailing list > > Freedos-user@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/freedos-user > > > _______________________________________________ > Freedos-user mailing list > Freedos-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/freedos-user _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
