# Help with Picaxe and serial LCD

December 27, 2008

Ok Picaxe Basic Gurus... I think I need some code snippits...

My new serial enabled LCD just arrived and I can't seem to get it up and running. I am using what I think is the standard picaxe basic commands but I am only getting white blocks, x's and some other random symbols. To be honest, I am confused with a lot of the serial commands in general, the whole ASCII thing and anything written as 0x7C or 0x14 or whatever.

For instance, I first need to change the baud rate. The instructions tell me to send 124 followed by "<control>k" . Now it seems the picaxe standard is 2400 baud. What is the actual command? Do I send the "change baud" command at 2400 baud when the display is at a default of 9600? and then the command number is 124 and also 0x7C so what do I do?

In my mind (and to show I have no idea what I am doing) here are all the options I can see:

serout 7,N2400, (124, "<control>K")

-or-

serout 7,N2400,(124)

pause 5

serout 7,N2400,("<control>K")

-or-

serout 7,N2400,($7c, "<control>k")

I could go on and on with my guessing but nothing is working.

In general, I assume my major problem is with the baud rate, I hope and assume that after I get that fixed I should be able to return to the standard serout 7,N2400,("Hello") sorta commands.

Would anyone be so kind as to give me a crash course on what you think I should know?

## a third range!

There's the odd numbers (binary ends in 1).

There's the even numbers (binary ends in 10).

And now I am starting to see a third range, dividable by 4 (binary ends in 100). Let's call them fourables.

Looking at the graph, you would expect these to form a set of plots under the even numbers. Starting at result 27 lowering towards result 17. Those are "The Unprintables" (Chris, you wrote those as "white squares", or just left them empty).

I now start wondering if there is a range of eightables, sixteenables and even thirtytwoables as well.

## BINGO is his NAMO!

The Grand Unified Bughas been found! I think...The clue was indeed in the "eightables, sixteenables, thirtytwoables". There's even a "sixtyfourable"!

Now count the binary digits between the parentheses and shift the number by that amount to the right. That's the same thing as dividing by the divisor mentioned. Once more in a table:

What-ables?bin ends in (LSB)

divide byor rather,shift how many positions?

The new theory now is that the numbers get pushed from the picaxe to the serlcd LSB first (the least significant bit goes in first). But the receiver does not see any start bit, because the polarity is wrong. So it ignores all

zeroesuntil it receives aone. Thatoneis interpreted as a start bit and then thrown away. Then it finally starts to read whatever is left over. In the case of an odd number, that would be the remaining six bits. The even numbers (that are not in any of the other ranges) leave five bits of actual data, resulting in the lower, but still printable range.All the others exist only in my imagination, but they fit the theory.

There are still two bugs, but the second derives from the first.

zeroesbecomeonesandonesbecomezeroes(this isprobably an electricalissue!)one(which is now inverted) becomes the new start bit. Effectively shifting the data to the right. Pad withzeroes(realzeroesas far as lcd is concerned) on the left.Call for review: I do not trust this analysis off hand. There is just too much room for errors and misinterpretations. Would someone with real knowledge of RS232 please check my exalted claims!Thanks,

Rik

## Calibfreq

Nice detective work!

You don't mention wheterh you are using the internal oscillator or a crystal. The timing of the internal oscillator can vary and has caused problems in recognizing the first legitimate character with other commercial serial devices. RevEd includes a Cailbfreq command to tweak the timing. This only is needed when using the internal oscillator,

Happy New Year!

Myc Holmes

## Good thinking!

## Start bit or polarity?

Ok, so Chris tried the polarity both ways up near the start without luck, and you seem to have gone to a lot of effort to prove the lack of a start bit which I said was the most likely problem at the start, but!

This is not an "I told you so" as Voodoo found some code by someone who has had the thing working from a picaxe. So is the unit faulty or is it another problem?

You got so wrapped up in playing "find the pattern" that you have not told us what you believe your results imply. (I'm willing to accept your code cracking efforts as accurate). If it is an "electrical issue" then what? That the serial backpack is faulty?

Hmm... I did also say something about exchanging the unit as it was possibly faulty.

Oh well, back to auditioning Orion slave girls, it's a tough job but someones got to do it! :]

## all valid points

These are all valid points.

And I LOVED the pattern finding. Just chalk it up to drainbamage. I were intentionally being vague about the electrical problem, so you guys could take it from here. And I could return to cutting cardboard prototypes.

Plus, what the heck do I know about electrons...

## About as much as I do about programming.

## Good job Rik. Did you use

## don't be silly

I have an entire room filled up with a cardboard enigma machine here!

Plus a little MS Office Excel filling up an entire hard drive....

## inversion indeed but first a shift

Cracked the odd range:

To get from a given value to observed output,

shiftyour bits one position to the right, theninvertbitwise. No more than seven bits per character!The decimal conversion (from which I derived the bitwise conversion) goes: result = - (given / 2) + 128 .

In picaxe basic this would be:

#picaxe28x1

symbol given = 33

symbol result = b1

let result = given >> 1 ' >> works only for X1 or X2 parts

let result = INV result

This does not work for the even numbers.

Yet.

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