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hp50g grobs - Printable Version

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hp50g grobs - Glenn Shields - 12-13-2009

I'm a new member and HP50g "trainee," got the printed manuals from
hpcalc, noticed a few examples with a long hex number for a graphic
(20-4 in user guide or 2-39 in AUR). Tried to relate the pixels with the hex digits, but can't figure out the connection; tried putting rows of pixels as 0's and 1's and going to hex, but still a mystery. Any help would be greatly appreciated.

Re: hp50g grobs - Vieira, Luiz C. (Brazil) - 12-13-2009

Hi, Glenn;

Please, have a look at page 22-30 (HP50G User´s Manual). Chances are that the example there elucidates better.


Luiz (Brazil)

Edited: 13 Dec 2009, 2:58 p.m.

Re: hp50g grobs - Glenn Shields - 12-13-2009

Thanks for the quick response, Luiz, I need to read that part again, slowly. In the AUR "walker" example, it states that the
programmer first compiles the image interactively in the Graphics
environment, then returns it to the command line. Even if I could do this, I am still wondering, for example, what part of
"E3001400...2800" represents his eye, or if this long number was
recorded "after the fact". Meanwhile I will be hitting the books!

It is an honor to be a part of this forum. I am more of a hobbyist, though I do have a BA in math. One of my tests of the new calc was to have it cycle through the rand.# generator given with the 15C (7 digit decimal x 997, FP) and do this 500,000 times to complete the cycle. My old 20s took a day and a half, but the 50g did it in hours! Looking forward to more interesting posts.


Re: hp50g grobs - Dave Britten - 12-13-2009

Check out comp.sys.hp48 sometime. You'll find more technical discussion about the 48/49/50 series there. Which isn't to say that you shouldn't stick around here too!

Re: hp50g grobs - Vieira, Luiz C. (Brazil) - 12-13-2009

Hi again, Glenn;

Thanks for your very welcome words. Although I'm also a guest (and also honored to be) here, I think I know exactly what you mean. So, if you folks allow me, 'Welcome!'.

About GROBs: James Donnelly's 'The HP48 Handbook' is one of the must concise and serious source of basic information about the HP48 and its 'daughters'. From his book, p.34:

Graphics Object Structure

A graphics object is structured as follows:
<header> This is a five nibble (1/2 byte) field that distinguishes a graphics object from any other object type, and has a fixed value of #02B1Eh.

<length> This field is a five-nibble quantity that contains the distance in nibbles from the start of the length field to the nibble past the end of the object. This length is #Fh + the number of data nibbles.

<height> This field is a five-nibble quantity that specifies the height of the graphics image in pixels.

<width> This field is a five-nibble quantity that specifies the width of the graphics image in pixels.

<data> The data nibbles begin at the upper-left corner of the graphics object and proceed left-to-right, top-to-bottom. Each row must contain an integral number of bytes, so the data may be padded with garbage bits. The bits in each nibble are written in reverse order, so the leftmost displayed pixel in a nibble is represented by the least-significant bit of the nibble.

If you are preparing a graphics object on a personal computer, remember that the HP 48 CPU reads data from memory into registers in reverse order, so the first four fields are written backwards. For example, the header is written ElB20.

Graphics objects may be entered into the command line on the HP 48. To enter a blank graphics object, type GROB width height, where width and height specify the size in pixels.

I hope this is a bit more helpful.


Luiz (Brazil)

Edited: 13 Dec 2009, 6:54 p.m.

I forgot to mention... - Vieira, Luiz C. (Brazil) - 12-13-2009

... three of the most important publications: Willian C. Wickes´ 'HP48 Insights'. It has three volumes, the two first ones about the HP48S and the third one about the HP48G.

These three books are available at the MoHPC DVD set.


Luiz (Brazil)

Another example from Donnelly´s book - Vieira, Luiz C. (Brazil) - 12-14-2009

From Donnely´s 'The HP48 Handbook' we can also pic the following example (p. 35).

To enter a graphics object which represents the letter "G" in the small font, type:

GROB 4 5 E010D090E0
The bit-mapped representation of the resulting graphic can be understood like this:

On a personal computer, the graphics object looks like this:

E1B20   B1000   50000   40000   E010D090E0
header length width height data

Now, consider a blank graphics object the size of the HP50G display with the "G" from above in the upper-left corner. The graphics object looks like this on a personal computer:

E1B20                               header
FAA00 length (changed for the HP50G)
38000 width
05000 height (changed for the HP50G)
E000000000000000000000000000000000 row 1
1000000000000000000000000000000000 row 2
D000000000000000000000000000000000 row 3
9000000000000000000000000000000000 row 4
E000000000000000000000000000000000 row 5
0000000000000000000000000000000000 row 6
2720 total data nibbles (HP50G LCD) ...
0000000000000000000000000000000000 row 80
I think that these examples are much better to actually 'see' how the GROB is built.


Luiz (Brazil)

Edited: 14 Dec 2009, 1:24 a.m.

Re: Another example from Donnelly´s book - Glenn Shields - 12-15-2009

You guys are amazing, thanks for your collective generosity and encouragement. I got my answer (the little walker's eye is in the digits 0015) but more importantly, you opened my eyes to a lot more. Happy Holidays Glenn in West LA (the city)