What four signals? Are you talking about the four (or eight) data signals again? In which case it's a strange question -- but we are used to them by now
They are data signals... if the display is just sitting there displaying something and you don't send anything to it, the data doesn't change, the signals don't change either, and there is no "frequency".
When you are sending something, you are in full control over them. They are not operating on their own at different frequencies. They have to all be set up before you toggle the E line to clock in the data. If you were to measure them, the result would depend on what is being sent and how often.
Regarding the ebay item: If you can read chinese and want to rely on boards that can "Various brush Airport together" (their words), it's your choice. Good luck!
Hi Hideki,
Ok, first things first.
Regarding "Various brush Airport together" I am glad to learn where that came from. I'd seen that referenced around here and I didn't understand it - but now I get it, I think. All I know is that the folks I've bought stuff from in China speak a lot better English than I speak Chinese.
Next up, regarding my strange questions - I resemble that remark
. Seriously, I saw your
face and I know it was meant with good affection - not to get too weird here.
Seriously, I appreciate you and everyone else putting up with my homemade self-study curriculum and learn a step at a time pace.
On to some content - I simply probed the four pins D4-D7 on the LCD (which I also observed with my LA which lets me see when the four pins/signals go high and low relative to one another). To be square (no pun intended), I'm not sure what I expected to see on these four pins. I probed these after having uploaded a sketch from the IDE to the Arduino - which results in some text displayed on the LCD. After the upload was completed was when I probed the pins with the scope and observed the signals on the pins with the LA. I assumed that these signals represented four of the eight bits needed to send the characters (text) to the LCD.
I studied Table 14 on the Hitachi datasheet:
https://www.sparkfun.com/datasheets/LCD/HD44780.pdf- what it shows is that characters are made up of Upper 4 Bits and Lower 4 Bits. So, using my LA's ability to aggregate 4 single bit waveforms (with each waveform showing transitions between 1s and 0s), I setup the Group function so that the 4 bits were summed to represent a 4 bit Byte; at that point I tried setting triggers to find any proximities between what might have been Upper Bytes and Lower Bytes in a valiant effort to see if I could detect combined 8 bit Bytes that could possibly be the ASCII characters rendered on the LCD.
I know, crazy, but so far it's been a good day. I even figured out how to change a fuse on the Atmega (more on that later).
Anyway, back to the 4 signals that I measured at the 4 pins - the frequencies I saw were after the sketch had been uploaded to the Arduino and displayed on the LCD. Not text was changing - so I don't know why there would be activity or what activity would be on those 4 lines - unless (I thought, perhaps) the text is continually refreshed from the Uno to the LCD. In the process of trying to figure how the text moves from the Uno to the LCD I measured the frequencies (after the upload from the IDE to the LCD).
That's my story (so far on this project) and I'm sticking to it. Questions/comments/suggestions all welcome. Thanks! EF
PS, there is definitely activity on the 4 LCD (D4-D7) pins - even after the sketch has been sent from the IDE to the Uno to the LCD. The first image below (from the Logic Analzyer) shows a triggered state but when the trigger is off there are continuous transitions on all 4 pins/lines/bits. Silly me, but I surmised that since there are 4 pins - each carrying 1 bit (toggling high and low), and since the LCD supposedly combines two 4 bit Bytes into one 8 bit Byte, that perhaps every fourth 4 bit Byte would be the companion Upper and Lower Bytes. It turns out in the Logic Analyzer screen shot that we happen to have the two 4 bit Byte sequences - 4 Bytes part - that make up the letter "I" which -- happens to be one of the characters from the sketch that is displayed on the LCD. You can see 1001 at the A cursor and 0100 at the T (trigger). I know.... "strange".