Example egpc
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, it will read/write/configure the 3 ports (ports A, B and C) on the GPIO header.
The egpc project builds one executable: egpc.
Contents
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 executables to the target system.
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Usage and Behavior
egpc reads/writes/configures the GPIO ports.
Hardware Requirements
The egpc C example project will run on any EMAC carrier board which has one or more GPIO.
Using egpc
./egpc device [d/c/i] arg
device is /dev/porta, /dev/portb or /dev/portc
d/c/i specifies the port command : d (data), c (configure) or i (index)
arg is either a port index or a bitmask. The bitmask is in hex format, range [0x00,0xff].
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 Port A to be an output.
./egpc /dev/porta c 0xaa
...and this reads the current pin configuration state of Port A.
./egpc /dev/porta c 0xaa
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 pin output latches on Port C to alternating high and low.
./egpc /dev/portc d 0x55
This flips the pins, writing all the pins that were set low in the previous command to high, and vice-versa:
./egpc /dev/portc d 0xaa
This reads the current pin data state of Port C.
./egps /dev/portc d
The pin values for Port C are displayed on the board's strip of 8 LEDs. Observe that the LEDs change state when a new value is written to Port C. This only works for Port C, however. Ports A and B must be read with an oscilloscope, multimeter, logic analyzer or similar device.
Usage Example. Port Index
./egpc device i (index)
If an index is specified then it sets the port's index
If an index is not specified then the port's current index is retrieved.
For example, this sets the index of Port A to 1
./egpc /dev/porta i 1
...and this reads the current index of Port A
./egpc /dev/porta i
Summary
egpc is an application which demonstrates reading, writing and configuring the GPIO ports.
