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USB Modem /w AT Commands?

R

route66

Senior member
I am looking for a USB modem, that when I connect it my computer it shows up as a new COM port - I can then open the COM port and send AT commands (such as ATD, ATA, etc). Comp USA has several USB modems, but they don't advertise if they have an AT command set and if they are or are not Winmodems.
 
All USB modems are soft modems just like most PCI modems. But they all have some version of the AT command set. Whether you can find an AT command reference for a given modem is problematic. I asked tech support of the mfr of my current external serial modem (Accent division of D-Link) where I could find the ATCR for it, and the guy on other end of the line sounded like a deer in the headlights looks... Duuuuh just doesn't cover it.
. Most of them use the basic set, it's just when you get into the new extensions (like for the v.92 protocol), etc that there may be some unique commands. If you dig around on the driver CD that comes with the mode you'll usually find at least a partial reference.
. IAC, I'd suggest getting a real external serial modem. If your mobo doesn't have an RS-232 serial port, then get a PCI serial card too, set up the port, connect up the modem and you can do whatever you want. AFAIK, only US Robotics still sells a true hardware PCI modem now.

Anyhoo, go to http://www.TechIMO.com/reviews/ and check out my review of the Accent modem. I found one on eBay for a guy and he never sent me any nasty message afterwards. So I guess he didn't think it was a POS either. They sell it at Office Depot - house brand (Aptiva or something like that... It's the best modem I've ever owned and if you read my review you'll know a lot more about it than the folks that are selling it.

.bh.
 
The reason why I want USB is because I develop a lot of embedded applications, and I need to isolate my computer/notebook from my components. Because of this I don't want to connect a serial port, modem or USB directly to an embedded device being developed - so by using a USB Hub and connecting all my devices to the USB hub there is at least some isolation from my computer/notebook to the embedded device being developed (don't want it to blow up my computer). I would prefer USB over serial because it's a lot more convenient to power the modem from the USB Hub instead of needing another power brick plugged in.

I really don't need to know all the AT commands, but support for the basic ones like ATD, ATA are necessary. That is sad to hear that the USB modems are soft modems, especially considering how much a USB modem costs.

You say that the USB modems have an AT command set - does that mean USB modems show up on your computer as a COM port?
 
Yes, the driver will create a "virtual" COM port type port address and IRQ, but they won't be the ones normally used by serial modems like EF8 IRQ 4, etc. but will usually be assigned a COMx: Proxy between 1 and 4. If not you could probably assign a proxy yourself thru the Add/Remove Hardware tool. Just Add a COM port and assign it the port address and IRQ assigned to your modem. Your software can then use that COMx: proxy to access the modem. You can look in device manager and find the port address and IRQ that were issued to your modem. They have surge suppressors for serial ports. The good ones have Transorbs in them - very fast. Sometimes built onto the add-on serial card itself on the best ones. Modems have to have some surge suppression on the phone line side, but that's to protect the Phone system from your modem, not vice versa.

The user guide or reference manual for most modems are sometimes printed and sometimes on the driver/software CD as a .PDF or .DOC file or sometimes you can get a more thorough reference online. They will usually give the most common AT commands that the modem supports. BestData and/or Zoom modems web sites have pretty thorough ATCRs for the Conexant chips. And check http://www.modemsite.com for lots of modem references and links.

.bh.
 
USB modems will offer a COM port, but it will NOT use ANY of a legacy COM port's resources - neither IRQ nor I/O registers.

Hence, half-legacy software that expects a COM port _driver_ to talk to will work ... but truly old software that expects ISA-bus-style COM port _hardware_ won't.
 
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