rreinold / networkedethernetcamera

Capture, transmit, and display an image with bit-level control

Sending an image over Ethernet using C##

Robert Reinold

b1_photograph_and_transmit.c

Purpose:

This code is designed to be run on a standalone NIOS board, with a peripheral camera attached, and an ethernet cable connecting this board to a second board.

Responsibilities:

1. Take photo by allowing camera to write to flash memory
2. Compress image (see explanation below)
3. Upon hitting the transmit switch, enter Transmit state and send first packet
4. Upon receiving an ACK, send the next packet until all 30 have been sent

b2_receive_and_display.c

Purpose:

This code is designed to be run on a standalone NIOS board, with a VGA connection to a monitor, and an ethernet cable connected to the first board.

Responsibilities:

1. Store 30 incoming packets
2. Decompress image
3. Display image via VGA output

How do we compress image comprised of 8bit pixels?

Each pixel is an 8 bit value with only one relevant bit, which represents a black or white pixel. Each pixel only requires one bit to convey presence of black. Thus, we take the single significant bit from the 8bit pixel, and pack eight of them into one char via bit masking and shifting.

/**************************************************************************

• Copyright � 2004 Altera Corporation, San Jose, California, USA. *
• All rights reserved. All use of this software and documentation is *
• subject to the License Agreement located at the end of this file below.* / /*****
• DANGER ** WARNING ** Please read before proceeding! ** WARNING ** DANGER *

---

• This program is an example of a "free-standing" C application. If you
• modify this example and try to call C library functions such as printf, they
• will NOT work unless you explicitly initialize the system, such as in the
• hello_alt_main software template. Please see below for details.
• Description

---

• A very minimal program that simply shifts an LED back and forth.
• Requirements

---

• According to the ANSI C standard, freestanding programs "own" the hardware,
• and cannot rely on system-services or device-drivers being initialized prior
• to program-start. A freestanding program is responsible for initializing all
• hardware devices, device-drivers, and system-services. Many embedded
• programs are, by nature, freestanding. The author relinquishes any illusion
• of running their program on a workstation.
• This example is a freestanding program because it's entry point is the
• function:
• void alt_main (void)
• As opposed to "main()" as a "hosted" application would (see the
• "hello_world" example).
• Upon entry to alt_main():
• • The CPU's caches (if any) have been initialized.
• • The stack-pointer has been set.
• • That's all. The rest is up to you.
• If you modify this example and try to call C library functions such as
• printf, they will NOT work unless you explicitly initialize the system.
• If you wish to use C library calls, it is strongly suggested you start
• with the hosted hello_world template which uses main() as it's entry
• point.
• On the other hand, if you want to write a program that gets-in even
• earlier, you will need to provide your own assembly-language machine-setup
• code by defining the symbol "_start". Any definition of _start in your
• directory will override the library definition. You can find source code
• for the Nios II library _start here:
• /components/altera_nios2/HAL/src/crt0.S
• This software example requires a system with a PIO peripheral named
• "led_pio". The software example will run on the following hardware
• examples:
• Nios Development Board, Stratix II Edition:
• • Standard
• • Small
• • Full Featured
• DSP Development Board, Stratix II Edition:
• • Standard
• • Small
• • Full Featured
• Nios Development Board, Stratix Edition:
• • Standard
• • Small
• • Full Featured
• Nios Development Board, Stratix Professional Edition:
• • Standard
• • Small
• • Full Featured
• Nios Development Board, Cyclone Edition:
• • Standard
• • Small
• • Low Cost
• • Full Featured
• Peripherals Exercised by SW

---

• The hello_led.c program simply shifts an 8-bit variable back and forth,
• writing the variable's value to the system's LED PIO peripheral on every
• iteration.
• Software Files

---

• hello_led.c - Main C file that contains the simple led manipulation routine.

*/