You may or may not have noticed the pretty green new banners that have appeared at the bottom of this page and atop the forum advertising the Matrix Orbital NK204-V LCD. This being a Bit-Tech promotion and me being a Bit-Tech member does make me a little biased but it's not hard to see how good this offer is; £33 is almost half the price of Milford's 4x20 serial LCD (which is frankly dreadful), and cheaper even than the unwired parallel 4x20 LCD that Maplin sell. In this article I plan on showing you exactly what you get for your money, how to attach it to your computer and make it work for you, and how to use some of the more advanced features that this LCD sports (namely GPO's and the keypad interface).
I seem to have jumped in at the deep end; if you're confused by anything I've said or want to know more about LCD basics then I'd recommend reading this.
Firstly, an introduction to the LCD. It carries the product code NK204-V and we can extract all of the specifications of interest from this:
NK - This is an LCD without a keypad interface. 'But you just said you were going to show me how to use the keypad interface; you're not making sense.' I know, I'm sorry. This LCD does have a keypad interface, it just doesn't have a connector soldered on to the PCB for a keypad to be plugged into (so Matrix Orbital are lying, not me!). The reason the connector was left off of this LCD is that unlike all other Matrix Orbital LCD's, the keypad controller on this display doesn't like two keys being pressed at the same time. This is a minor point though and later on I'll show you how to add a keypad connector to this display's PCB and also how to use it.
204 - This LCD can display 20 characters per line and 4 lines at once. Almost all LCD's conform to standard display and PCB sizes; this means that this like most 20x4 LCD's won't quite fit in a 5.25" single drive bay... so if you're wanting to install this into your case make sure you have two 5.25" drive bays free (Matrix Orbital sell a double drive bay insert for easy mounting if you decide to take this option).
V - This LCD has a voltage regulator on board. This allows an input voltage for the LCD of anywhere between 7 and 15 volts (I'll be using 9V) and hence if your supply isn't very clean it shouldn't affect the LCD's performance. LCD's without voltage regulators can be permanently damaged by a voltage fluctuation of just 10%; it's good to have one.
Ok enough waffle. You've ordered your LCD, you wait 2-3 days for UPS to deliver a nice box to you doorstep and open it to find...
I've marked out some areas of special interest on the back of the LCD. I'll be using most of these in this article so I thought it best to introduce them properly!
1. This is the serial interface connector for the LCD. There are also a couple of spare pin holes just below this connector if you'd prefer not to use the standard serial cable. I'll show you what type of serial cable you'll need on the next page.
2. The missing keypad connector. I'll show you how to add a connector to these holes towards the end of this article.
3. The General Purpose Output connectors (GPO's). Basically these can switched between 0 and 5V by the serial controller - I'll show you how to use these and why they're useful in a short while.
4. A few jumpers to change the default communication speed - you should have no need to touch these.
5. The pins connecting the bare LCD to the serial controller - these are a permanent connection between the two and are a bit of a pain later on when access to the underside of the controller would be nice (for adding a keypad connector).
6. The voltage regulator.
7. The power connector. You can also control the LCD through the middle two pins of this connector, but I won't be. This isn't the correct connector for use with a floppy drive power cable, but it's close enough.
I think I've given you a fairly good introduction to this LCD; now it's time to connect her up.