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GLK19264 Rev 2 Strip Chart

Posted: Thu Aug 14, 2014 5:37 pm
by dr21702
Looking at the documentation for GLK19264 Rev 2 I see that the strip chart commands have been changed and the old command no longer available. My attempts to render strip charts using the newer commands produces bizarre results and the documentation of the parameters is practically non-existent.

What is the purpose of the min/max value parameters? How do these work in relation to the height of the strip chart? Is is scaled? Are the short values signed or unsigned?
The style types are also quite vague as well...what is the difference between bar/box and separated bar/box?

As a test I tried to create bar strip chart 192 wide by 40 pixels high with values from 0 to 40, 5 wide step:
254 110 1 0 0 191 39 0 0 0 40 5 0 0 0

Then sending a sending values from 1 to 10:
254 111 1 0 1
254 111 1 0 2
254 111 1 0 10

One would expect this would be a series of bars each one pixel higher. What I end up seeing is a bunch of bars ranging from zero to three pixels high ending with a final bar that actually extends below the bottom of the chart bounds which makes no sense. Is there a sample program or further documentation on how these strip chart parameters work?

Re: GLK19264 Rev 2 Strip Chart

Posted: Fri Aug 15, 2014 10:07 am
by Raquel

Thank you for posting on the forum.

You are correct, we have changed the implementation of the old strip chart that was only able to scroll in 8 pixels.
I apologize that the documentation may have not been too clear and therefore causing you troubles in setting up / drawing strip charts.

The biggest thing I see is the order of the data for short (16-bit) parameters. We implement little endian, and I think you are sending them in big endian order.
If you please re-try your initialization like this:
254 110 1 0 0 191 39 0 0 40 0 5 0 0 0
and your values as:
254 111 1 1 0
254 111 1 2 0
254 111 1 10 0

The min/max value parameters scale the value provided, eg. for your height of 40 with min of 0 and max of 40 (ie range is 40), each value is 1 pixel height.
Both the min/max parameters, and value (command 111) are signed shorts.

As per strip chart type, bar is a rectangle with no fill, and box is a filled rectangle; separated bar/box means a 1 pixel empty spacer is added in between the bar or box.
I will bring your comments regarding further documentation or even an example on strip charts to our technical writer.
We hope to better the manual so as to make use and implementation of display features easy.

Thank you,

Re: GLK19264 Rev 2 Strip Chart

Posted: Fri Aug 15, 2014 9:00 pm
by dr21702
Thank you the information. Fixing the endian resolved the primary issue. I did find that the chart will draw erratically if you set chart values far outside the minimum/maximum range so that should be avoided.

I am seeing one more oddity that I cannot resolve in that strip charts will not render on the highest value pixel row.

For example, I define a chart same as above (with the correct endian) of 40 pixels high with value from 0 to 40:
254 110 1 0 0 191 39 0 0 40 0 5 0 0 0

Then set the chart values 39 and 40
254 111 1 39 0
254 111 1 40 0

On the display I get 2 bars of equal height both 39 pixels high ending on Y coordinate 1. Shouldn't the second bar be 40 pixels high ending on Y coordinate 0?

Re: GLK19264 Rev 2 Strip Chart

Posted: Mon Aug 18, 2014 1:49 pm
by Raquel
You are right, the bars should not be equal; 40 should be a pixel higher than 39 such that value 40 should have ended on Y=0.
There is a bug on the code, if you please pm your email address and I can try and send you a firmware update.
Thank you,