Example io demo

TODO: {{#todo:InProgress(12.05.13-12:47->JG+)|Jgreene|oe 4,oe 5,jg,md,Review}}

This is a guide to the io demo C example project included in the EMAC OE SDK.

The io_demo project provides four examples of carrier board IO:

• An analog-to-digital converter demo.
• A counter demo.
• An input-to-output demo.
• A ring demo.

The io_demo project builds one executable: io_demo.

Opening, Building and Uploading the Project Files

1. Open the C/C++ editing perspective.

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2. Open the project files.

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3. Build the project.

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4. Upload the binary to the target machine.

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Usage and Behaviour

Hardware Requirements

To use the io demo program you will need the following hardware.

• An EMAC carrier board: SOM-150ES, SOM-200ES, SOM-210ES, SOM-212ES or SOM-250ES.
  
• A compatible EMAC SoM for that carrier board (SOM-9260M, SOM-9G20M and SOM-9X25 are all compatible and available from EMAC).
  
• A multimeter or oscilloscope. See Usage Example. Input to Output Demo and Usage Example. Count Demo for details.
  
• A ribbon cable just long enough to reach from GPIO Port B to GPIO Port C. See Usage Example. Input to Output Demo for details.
  

File:Som150 with SoM.jpg

This is a SOM-150ES carrier board carrying a SoM

Usage for io_demo

Run io demo from the console. It takes no parameters.

 ./io_demo

This brings up a menu of demos.

****************************
     Demo Menu              
                            
A/D Demo             - a    
Count Demo           - c    
Input to Output Demo - i    
Ring Demo            - r    
                            
Exit                 - x    
                            
Enter Selection:

Now we can press a,c,i or r to run a demo; or x to exit.

Usage Example. A/D Demo

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did somebody say something about there already being an analog out built right onto the carrier board?

Usage Example. Count Demo

From the demo menu press c.

The system counts from 0 to 255 in binary. It takes about 15 seconds to complete.
The steps of this process are reflected in the GPIO PortC header pins. As each bit in our 8bit register is set to 1, the corresponding pin in the PortC header momentarily registers 5 volts (easily detected with a multimeter or oscilloscope).
More visibly, the process is also reflected in the strip of 8 LEDs on the board (LD1-LD8). A lit LED indicates a 1 in our 8 bit register and an unlit LED indicates a 0. When the counting process is finished all 8 LEDs are lit (255).

File:PortABC gpio header and LEDs location.jpg

Locations of the GPIO header and LED strip on the SOM_foo carrier board

File:Gpio portc detail.jpg

Details of GPIO Header : Port C. Note that half of the GPIO header is ground. Also note that Port C starts on the second header pin.

Usage Example. Input to Output Demo

In this usage example the SOM-150ES carrier board talks to itself. We send an 8bit data stream directly from Port B to Port C via a short piece of ribbon cable.

<detail of board. gpio header closeup with ports b and c labelled>

This is the ribbon cable that we made for our input-to-output demo. Note that we connect PortC:pin0 to PortB:pin0; PortC:pin1 to PortB:pin1; etc.

Here's our cable plugged into the GPIO header. You see that PortC:pin0 outputs to PortB:pin0; PortC:pin1 outputs to PortB:pin1; etc.

Our data stream for each pin is 1,0,1,0,1,0... That is to say: all pins are set to 1, then they are all set to 0, then to 1 again, etc. We observe our data stream in the strip of 8 LEDs on the carrier board. They blink in unison.

NOTE The blinking may get a little out of synch after a few seconds.

<pic> (animated GIF?)

Usage Example. Ring Demo

Refer to the SOM-150ES carrier board surface mount LEDs LD1-LD8 for output.

500px

The board lights the LEDs in numeric sequence, 1-8, then repeats; looping until a key is pressed.