NUE-PSK Digital Modem
Having problems with your keyboard? The prescription is probably here!
The NUE-PSK Digital Modem was designed to use a standard AT-style "PS2 keyboard" as its data entry device. This is the keyboard that has been commonly used with PCs for many years, and its cable with a 6-pin mini DIN connector plugs right into the modem.
A dual mode USB/PS2 keyboard also works with the modem when used with one of those little USB-to-PS2 adapters. The modem software commands the keyboard to lock into the PS2 mode when the combo keyboard is detected.
The PS2 protocol for communicating with the host it is plugged into is somewhat bizzare to the uninitiated. It consists of multiple scan codes being sent serially over a data line to the host while another line clocks the data into the host data port. Everytime a key is pressed or released, a scan code is generated. Every key on the keyboard generates a unique scan code which the host software (e.g., the NUE-PSK software) must interpret and take action on. This prototcol offers the flexibility for applications needing control over the keyboard, and some applications do not use all the capabilities offered by a given keyboard.
Such is the case with the NUE-PSK modem at present. The modem does not need certain keys, so in most cases it just ignores those keypresses. The keys used in the modem software include: alphas, numerics, function keys, arror keys, backspace, shift, control+key (some), and the symbols accessed by the shift+number keys. A key that is currently unused is the Caps Lock -- lower-case text is transmitted faster in digital mode communications, so we opted initially to not bother with handling the Caps Lock function.
It is highly recommended that the keyboard be plugged into the modem before the modem is turned on. This general best practice with any electronic equipment helps protect the appliance from transients surges arising from "hot plugging" operations.
Normal Keyboard Behavior
1) When the NUE-PSK power is turned on, you will see the some or all the LED lights momentarily blink on and off as the keyboard is initialized by the modem and the keyboard runs its internal Power On Self Test (POST) functions.
a) Arrow Keys -- The right, left, up and down arrows keys move the cursor along the spectrum line showing the receioved data on the modem's dispplay. The left/right arrow keys move the cursor at normal speed, while the up/down keys move the cursor faster. See the manual for more details of
b) F8: TUNE -- Pressing F8 will display TUNE in the upper line of the LCD. This function keys the transmitter and delivers a single-tone frequency to the radio for tuning purposes. Pressing F8 again turns off TUNE.
c) F10: CONFIG -- Pressing F10 will display the Configuration menu on the LCD. Pressing the number of the displayed options will set perform those indicated functions. Pressing 0 will exit the Configuration menu.
d) F12: TX -- Pressing F12 places the modem into Transmit mode, as indicated by TX being displayed in the upper area of the LCD. The PTT line is also brought low in order to key the transmitter. Only now will general text characters be echo'd to the LCD, while simultaneously being encoded and delivered as modulated audio tones to the transmitter.
e) CTRL+O -- Pressing the CTRL and O (the "oh" alpha key) will toggle the the display backlight on and off, as desired. This keyboard command operates in either Transmit or Receive mode.
So the important thing to note here is that it is normal for most keypresses not to be echo'd to the display when you turn on the modem ... because the modem is in Receive mode! You need to put the modem into Transmit mode (F12) before seeing any typed characters appear on the display.
A recent finding also shows that pressing the Pause key will reset the modem. This is normal behavior, albeit unexpected. This condition will be changed in the next software release of the modem code, and until then you should not press the Pause key.
Abnormal Keyboard Behavior
We've found that most PS2 keyboards operate just fine with the NUE-PSK modem. However there are some cheap versions around from vendors who perhaps cut corners in their QA process, or who use controller chips inside their keyboards that do not follow the timing specifications too well.
In these cases, the keyboard might not react normally as described above. In fact, we've seen some keyboards that seem completely unresponsive when plugged into the NUE-PSK modem ... yet they work fine when plugged into a PC.
What to do if you have Abnormal Keyboard behavior?
All modems were functionally tested at the factory to ensure complete and satisfactory operation of the keyboard-invoked functions while using one of the keyboards here on our test bench. But you might actually have a bad keyboard, so you might try another keyboard to see if the problem persists.
If you have diligently gone through the checkout in the Normal Behavior section and the keyboard you really prefer to use still is not working right, please contact me at the email address in the footer of this page. We have been working on an upgrade to the keyboard controller chip in the modem and we could send you one as a replacement. It requires you to open up the modem, and unscrew and lift the LCD in order to access and replace the socketed DIP chip. If you are uncomfortable replacing the chip on your own, we could instead have you ship the modem back to us for chip replacement. Either way, drop me an email and we'll go from there.
73, George N2APB
Page last updated: April 21, 2008