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2.5.2 USB Interface Devices

With the disappearance of serial and parallel ports on most new PCs, most N1MM Logger+ users are now forced to use USB interface devices to accomplish functions formerly performed using serial and parallel ports. These include consumer-grade USB-to-serial adapters as well as devices designed and manufactured specifically for amateur radio use. For the most part, with the help of software drivers installed when the device is first connected to the PC, these devices are configured in N1MM Logger+ as if they were true serial ports, with some important caveats and exceptions noted in the following sections.

A separate category of USB devices is the "USB Sound Card", which are similar in function to on-board and bus-based sound cards except that its interface with the PC is through a USB port. Some devices aimed at the amateur community combine USB sound cards and USB-to-serial adapters in a single box. Some transceivers are now delivered with such USB devices incorporated internally. Generally speaking, once the appropriate drivers have been installed, these devices are configured in similar ways, regardless of whether they are in a transceiver or in a separate box or boxes.

 USB-to-parallel adapters generally will not work

USB-to-parallel adapters will not work for keying CW or controlling PTT through the standard parallel port interface, because these adapters do not permit controlling individual lines.

The only exception we are aware of is the SO2RXLAT by Piexx, which is designed specifically for this purpose.

1. General Comments on USB to Serial I/O Interface Devices

There are three different problems that are often encountered by N1MM Logger+ users trying to use USB-to-Serial adapters.

The first is loss of communications due to Windows powering down one or more USB ports. This problem and the solution are covered in this section.

The second of these problems relates to the specific chipsets and drivers used in these adapters. The market for these adapters is dominated by two chipsets, called Prolific and FTDI. There is a potential problem with adapters using the Prolific chipset for serial communications (in particular, for rig control) from N1MM Logger+. This problem only applies to actual serial communications; simple on-off keying of DTR and RTS for CW and PTT keying is not affected. There are several versions of the Prolific chipset (including counterfeit knock-offs), and also several versions of the drivers, and at least some of these drivers are incompatible with the Microsoft library routines used by N1MM Logger, DXLab Suite, Logger32 and some other amateur radio programs. The symptom is an error message with the error number 8020. The result is that with some combinations of Prolific chipset and/or driver software, adapters using the Prolific chipset may not work properly for rig control and similar purposes with N1MM Logger+. Rather than attempting to list all of the possible combinations of chipset version, driver version and operating system in order to determine which ones work and which ones do not, our simplest advice is to avoid using USB-to-serial adapters using the Prolific chipset for rig control, rotor control or similar serial communications purposes.

The third problem relates to FSK RTTY keying from MMTTY. MMTTY can use a true serial port for FSK keying, by programming the port to send 5-bit characters at 45.45 baud. Unfortunately, most single-port USB-to-serial adapters, or at least those that are new enough to work with Windows 7, cannot go slowly enough to do 45.45 baud Baudot. Some multi-port adapters (two or four serial ports from a single USB port, e.g. Edgeport) are capable of going slowly enough, but if there are currently-sold single-port adapters that can do direct FSK keying, they are few and far between.

The standard solution to this is to use EXTFSK (or EXTFSK64, on systems whose CPU is capable of supporting it). EXTFSK does all the timing internally instead of using the serial port hardware. EXTFSK is capable of keying FSK on any of the TxD, RTS or DTR lines on any serial port or any USB-to-serial adapter, and even on a true parallel port (but *not* on USB-to-parallel printer adapters, which are incapable of bit-twiddling). There is a downside to using EXTFSK - the timing is less accurate than the hardware timing from a true serial port. This may result in a slightly less readable signal under difficult conditions.

We are not aware of any USB-to-serial adapters that will not do FSK with the help of EXTFSK or EXTFSK64, nor are we aware of any USB-to-serial adapters that will not key CW or PTT on their DTR/RTS lines other than adapters that don't have any physical connections for these control lines (such as the Elecraft KXUSB which does not implement the DTR and RTS control lines and therefore cannot use DTR or RTS).

Drivers: One key thing to never do is to allow Windows to tell you that it already has the driver for a particular device - you should always install the driver that comes with your interface. Windows can misidentify these devices when you plug them in and Windows will let you fail by using the driver it thinks is correct - and often Windows is dead wrong.

Generally speaking, with XP you can use most any USB to serial device (Prolific or FTDI chipsets) as long as you do not have a conflict. When it comes to Vista or Windows 7, FTDI seems to be the only game in town for close to sure results (Editor's note - not all users agree with this characterization.)

Even with all of this, depending on what you have done with your computer previously, you may have problems. And again, the point of all of this is that the problems may have nothing to do with what hardware you are trying to use. It could be something left over by some earlier activity on your computer. That said, most installations of these devices goes well right from the start. When they do not, it can be very frustrating.

A further technical note, posted on the N1MM Logger reflector by Joe, W4TV, concerns an easy way to tell whether a given adapter can handle 45.5 baud RTTY:

Windows serial drivers set the data rate (baud rate divisor) with 14 bits of a "double word." That limits the max/min range of the driver/UART to 214:1 ... and any maximum rate higher than 512K will preclude operation at 45.45 bps.

The lower rates are not a 100% guarantee of compatibility but the higher rate is a certain sign that EXTFSK or AFSK will be required for RTTY.

2. Sound Interfacing and USB External Sound Cards

If you want to record your contest QSOs, or use stored messages in phone contests, you will need to interface your computer to the audio system of your transceiver.

This requires a little thinking ahead. If you wish both to record QSOs and to use stored messages, then you will need a sound device (be it internal or external) that has both Line and Microphone inputs, and that is capable of duplex operation - that is, it can both record and play back at the same time. This is not a rare capability, or something found only on expensive sound cards, but something to check in choosing which card to buy.

A more common problem, these days, seems to be sound cards - particularly those integrated into laptop computers - that have only a single input that can be used for either Line or Microphone, but not both at the same time. In those cases your best bet may be to get an external USB sound card. Again, it is not necessary to go high-end for this application, so long as both criteria above are met.

Two external USB cards that have been tested with N1MM Logger are the Encore, sold by NewEgg here .for under US$20, and the GWC, also sold by NewEgg at this URL for about the same price.. The ByteRunner UA-580 also works fine. (Thanks, Joe W4TV for this info)

3. CW issues with USB Adapters

N1MM Logger+'s serial and parallel port CW options are a simple and easy way to generate CW, but if your computer is slow, you may find the CW is not always smooth, particularly when receiving spots from a Telnet cluster in a busy contest. If this happens with serial keying, try using a parallel port if you have one. If you don't, or if you want to put an end to CW issues once and for all, the answer is K1EL's Winkeyer USB, which handles CW and all-mode PTT by offloading these functions from the computer entirely. It is also an excellent stand-alone keyer with 4 built-in memories.

Another issue can be poor weighting when using serial port keying. Some adapters have a lot of latency and will mangle your CW. Usually this can be corrected by finding a better driver for the adapter. Make sure you are running the latest vendor-provided driver for your operating system, not the one the OS picks. Some adapters allow you to set the latency in control panel. See this article.

Last Modification: 29 April 2016 06:25:48 EDT by n4zr.