Example egpc

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TODO: {{#todo:InProgress(11.13.13-14:31->JG+)|Jgreene|oe 4,oe 5,jg,md,InProgress}}

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

egpc is an application for reading/writing/configuring gpio character devices. Specifically, we read/write/configure the 3 ports (ports A, B and C) on the GPIO header.

The egpc project builds one executable: egpc.

Opening, Building and Uploading the Project Files

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


2. Open the project files.


3. Build the project.


4. Upload the executables to the target system.


Usage and Behavior

egpc reads/writes/configures the GPIO ports.

Hardware Requirements

The egpc C example project will run on any EMAC carrier board.


Using egpc

./egpc device d/c/i (mask)

device is /dev/porta, /dev/portb or /dev/portc
d/c/i specifies the port command : d(data), c(configure) or i(index)
mask is a bitmask in hex format in range [0x0,0xff].

Usage Example. Port Configuration

./egpc device c (mask)

If a mask is specified it configures the pins for input/output.
If no mask is specified it returns the current configuration.
mask is an input/output bitmask. 1=output and 0=input.
For example, this sets every other pin on PortA to be an output.

./egpc /dev/porta c 0xaa

...and this reads the current pin configuration state of PortA.

./egpc /dev/porta c     

Usage Example. Port Data

./egpc device d (mask)

If a mask is specified then it sets each bit's corresponding pin output latch to high/low accordingly.
If a mask is not specified then the current pin state is retrieved.
For example, this writes all pin ouput latches on PortC to high.

./egpc /dev/portc d 0xff

...and this reads the current pin data state of PortC

./egps /dev/portc d

Note The pin values for Port C are displayed on the board's strip of 8 LEDs. Observe that the LEDs change state when we write to Port C. This only works for Port C, however. Ports A and B must be read with an oscilloscope or multimeter.

Usage Example. Writing to Port C

We write a data bitmask to Port C. The values are rendered in our LED strip. (note that only PortC is displayed in the LED strip. Ports A or B would require kind of device to read them; a multimeter or oscilloscope or something like that.)

./egpc /dev/portc d 0x55

LEDs 1-8 are lit: 10101010

MIKE I was thinking that maybe we could have some kind of general purpose "know your board" images (I have created a few) or wiki pages. They would point out things like the GPIO header and the LED strip.

./egpc /dev/portc d 0xaa

LEDs 1-8 are lit: 01010101