COMMUNICATION PROTOCOL RS232 IMPLEMENTATION ON FPGA

NOVATEUR PUBLICATIONS
INTERNATIONAL JOURNAL OF INNOVATIONS IN ENGINEERING RESEARCH AND TECHNOLOGY [IJIERT]
ISSN: 2394-3696
VOLUME 2, ISSUE 12, DEC.-2015
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COMMUNICATION PROTOCOL RS232 IMPLEMENTATION
ON FPGA
MR.SHITAL N.GAVADE,
ME Scholar,
VLSI & Embedded, DKTE’s Textile and Engineering Institute,
Ichalkaranji, Maharashtra, India
PROF.R.N.PATIL
Associate Professor,
VLSI & Embedded, DKTE’s Textile and Engineering Institute,
Ichalkaranji, Maharashtra, India.
ABSTRACT
Communication Protocol RS232 Implementation on Field Programmable Gate Array (FPGA)
has been presented in this paper. The Image pixel values are converted into binary and send
to the FPGA from PC through Serial Communication Protocol .GUI is designed in MATLAB
and is used to interface Personal computer (PC) and FPGA. The image pixels are read
through FPGA in binary format.
INDEX TERMS: FPGA, MATLAB, Image processing, RS232, VHDL, Verilog. Etc
INTRODUCTION
FPGA generally consist of a system with logic blocks such as look up tables, gates, flip-flops
and some memory blocks all placed in the vast array of interconnects. The FPGA can be
reconfigured to a particular logic circuit using hardware description language like VHDL or
Verilog. The FPGA architecture allows large variety of logic designs for real time
application.
MATLAB GUI is used to communicate with the FPGA board. The Image is converted into
binary format and then using RS232 interface the pixel data has been sent to the board. This
paper gives a better idea to implement the RS232 Protocol on FPGA board. As the data is in
binary format the hardware required is less and processing is fast. Because of binary data one
don’t need to implement square root algorithm in Verilog or VHDL language.
DESIGN REQUIREMENT AND IMPLEMENTATION
2.1. RS232 PROTOCOL
The RS-232 serial communication protocol is a standard protocol used in asynchronous serial
communication [3]. In asynchronous serial communication the data is transmitted without
any clock signal to the receiver. Instead, special bits like start bit stop bit and parity bits are
sent along with the data bits to synchronize transmitter and receiver. When data has to send

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using asynchronous transmission a start bit is added at the beginning of the data and then data
bits along with parity bit and stop bit is added. Here parity bit is optional. In ideal condition
both Tx and Rx lines are held high. The length of data bits that can be sent are 5, 6, 7or 8 bits.
The start bit is ‘0’and the end bit might be 1, 1.5 or 2 bits in length with ‘1’value.
Figure 1: RS232 asynchronous communication data wave form
BAUD RATE CALCULATION
Baud rate is a measurement of transmission speed in asynchronous communication it
represents the number of bits that are actually being sent over the serial link
Spartan 3E starter Kit Operating Frequency= 12 MHz
Baud Rate = 9.6 KHz = 9000 Hz
Count = 12 MHz / 9000 ~= 625
For receiver the sampling is required so the Count is get modified for receiver
The flow chart to implement and generate the baud rate is given below. Here counter are
initiated to count the values shown in count. After reaching each value the counter will be
reset and start counting again. For each time counters reaching the terminal value, the baud
clock and sampled baud clock are set ‘1’
Figure 2: Flow chart of Baud rate calculation
START
INCREMENT BUAD RATE
COUNTER
BDCOUN
TER=625
S_CLOCK=0
S_CLOCK=1
Yes
No

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2.3 IMPLEMENT RS232 PROTOTYPE USING VHDL
The receiver block of the RS232 serial communication will run on the sampled baud clock
while transmitter block will run on the normal baud clock signal. The transmitter can also run
on the sampled baud clock but as switching will be more in sampled baud clock to reduce the
dynamic power consumption we will run transmitter block on normal baud clock signal.
The sampling can be done with 8, 16 or 32 samples. Here we are doing it with 16 samples.
The sampling is required because of the uncertainty of the start bit arrival, as it is a
asynchronous communication. The flow chart for receiver and transmitter is shown below. In
the receiver the counter need to be synchronized. As we are taking 16 samples the data will
be captured at 8th sample, so as soon as counter2 reaches 8th sample the data will be
received.
Figure 3: Flow chart of RS232 Receiver
Figure 4: Flow chart of RS232 Transmitter
START
TX_DATA-
0
INCREMENT COUNTER
COUNTER
=10
START RX_DATA
RECEVE THE STOP BIT
RECEIVE DATA
YES
NO
YES
NO
RX_DATA=1
START
LOAD DATA
COUNTE
R =10
SHIFT DATA
INC COUNTER
DATA
AVALAB
LE
No
Yes
Yes
NO

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MATLAB GUI IMPLIMENTATION
MATLAB has a very good Graphics User Interface development environment tool to develop
reliable and fast user interface. The binary image conversion is done easily with MATLAB in
build functions. Also serial communication prototype is implemented using MATLAB to
communicate with FPGA board via RS232. The MATLAB graphics use interface window is
as shown in below
In that the matlab design the GUI which is shown in the following fig in that the GUI
different tools are used like the radio button, push button, Edit button etc. and write the code
for the push button .here the two push button are used one for the load the image and another
used for the transmit the pixel values those button shown in the following figure
Figure 5: MATLAB GUI
3.1 CREATING MATLAB SERIAL PORT
Serial port= serial (‘com3’) //port creation
Setting Parameter of the Port

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1) Set (serial_port, ‘BaudRate’,9600)
2) Set (serial_port, ‘InputBufferSize’, totalpixels)
3) Set (serial_port, ‘OutputBufferSize’, totalpixels)
Writing and reading to/from the port
F open (serial port) //opens the port Fwrite(serial_port, [0,12,4,5]) //writing binary
data
A= fread (serial port, n) //reading binary data
//n indicates no. of data
Closing serial port
Delete (serial port), Clear serial port
In the following the flow chart seen that the how the interface the Matlab GUI and the FPGA.
Now the you are entered the port are connected FPGA board on MATLAB then you are press
the transmit command button then the pixel values are transmitted to FPGA form MATLAB.
Before transmitting the image pixel values these image are divided to the 8x8 Non
Overlapping Block. Suppose the you can used the 128x128 size of any image then first this
image are divided in 8x8 block and then send to FPGA by using the RS232 protocol.
Figure 6: Design low of the GUI
YES
START
ENTER THE COM PORT
RADIO
BUTTON
PRESS?
-LOAD ‘JPG’ FILE
- CONVERT THE RGB IMAGE
TO GRAY IMAGE
-RESIZE THE IMAGE
-CREATE THE 8X8 NON
OVERLAPPING BLOCK AND
CONVERT THE DECIMAL
PIXEL VALUES TO BINARY
VALUES SEND THE PORT
SERIAL PORT OPEN
WAIT FOR THE PUSH BUTTON
PRESSED
SERIAL PORT NOT
OPEN
LOAD IMAGE
BUTTON
PRESS?
TRANSMIT
BUTTON
PRESS?
STOP
YES YESNONO
NO

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3.2 STEPES FOR CREATE THE 8*8 NON OVERLAPPING IMAGE BLOCK
1) Read the size of the image(sz)
2) Find the No horizontal block and vertical block
Nr =sz(1)/8
Nc =sz(2)/8
3) Creating the 8x8 bock
for i=1:nr
indx_i=(i-1)*8;
for j=1:nc
indx_j=(j-1)*8;
Block=I(indx_i+1:indx_i+8,indx_j+1:indx_j+8)
4) These 8x8 block are converting in one dimensional array
stream=Block(:);
5) These array are converting to that ascii values
Ch_str=char(stream);
6) Finding the decimal values of the character
D=abs(Ch_str(ptr))
7) Convert the these decimal values to binary
B=de2bi(D,'left-msb',8)
8) Finally send the decimal values to edit tool by using the command
Set (handles.edit2,'string',stream(ptr));
And also send the binary string to the edit tool
Set (handles.edit3,'string',B_str);
IMPLEMENTATION AND SIMULATION RESULT
Here we have used 128x128 pixel images. While synthesizing the HDL code, we have used
internal FPGA RAM instead of on board memory, so the no. of LUTs used gone up to 90%
from the initial 20% value.
128*128 size of image are transmitted to Spartan 3 board via RS232 implement on FPGA
and display the pixel values on the LEDs are available on the Spartan 3 board shown the
following Matlab GUI simulation results.

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4.1 MATLAB RESULT
Figure 7: Select the port and Load the image
Figure 8: Transmit the pixel values to Serial Port(com8)

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4.2 RTL SCHEMATIC FOR RS232
4.3 HARDWARE RESULT
Figure 9: Transmit the pixel values of image to Serial Port (com8)on the hardware
sparton3 and displays the pixel values on LED

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DEVICE UTILIZATION SUMMARY
Table -1: Device xc3s50a-5tq144 Utilization
DEVICE –xc3s50a-5tq144
LOGIC
UTILIZATION
USED AVAILABLE UTILIZATION
NO OF SLICE FLIP
FLOPS
655 1,408 46%
NO OF 4 INPUT
LUT’S
615 1,408 43%
NO OF USED AS
LOGIC
615
NOOF OCCUPIED
SLICE
633 704 89%
NO OF BONDED
IOBS
13 108 12%
CONCLUSION
Converting Image to binary values will increase the efficiency of the system. Image
processing applications required large memories, due to this memory control logic become
vital in the image processing application. This Memory requirement problem has been
reduced in this paper by near about 50%.But RS232 serial communication is simple to
implement but the transfer speed is very less as compared to other communication
techniques.
ACKNOWLEDGEMENTS
Shital N. Gavade would like to thank Mr. R. N Patil, sir Lecturer guiding me through out to
complete the work successfully and would also like to thank the HOD sir , and other staff
members in the electronics and communication department for extending their help and
support in giving technical ideas about the paper and motivating to complete the work
effectively and Successfully.
REFERENCES
[1] Rashmi,Mukesh Kumar, RohiniSaxena “Algorithm and technique on various edge
detection,” An International Journal (SIPIJ) Vol.4, No.3, June 2013.
[2] Mr. Manoj K. Vairalkar, Prof. S.U. Nimbhorkar, “Edge detection of images using
sobeloperaotr,” International Journal of Emerging Technology and Advance Engineering,
Vol.2, January 2012.
[3] Han Xiaoru, Gao Yudong, “Design and Implementation of the Universal RS232-
GPIBInterface,”Electronic Measurement and Instruments, 2007. ICEMI '07. 8th
International Conference on.

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