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, we 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.
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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 [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 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 PortC to alternating high and low.
./egpc /dev/portc d 0x55
...and this flips the pins; writing all the pins that we just set to low to high and vice-versa.
./egpc /dev/portc d 0xaa
...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. 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 PortA to 1
./egpc /dev/porta i 1
...and this reads the current index of PortA
./egpc /dev/porta i
Summary
egpc is an application for reading, writing and configuring the ports on the GPIO header.
