Development of a Cost-effective Data Acquisition System using an

Open-source Hardware and Matlab/Simulink

Sugkil Seo, Yeong Sang Park and Young Sam Lee

Department of Electrical Engineering, Inha University, Incheon, Republic of Korea

Keywords:

USB Communication, Matlab/Simulink, Data Acquisition, Open-source Hardware, S-function.

Abstract:

This paper proposes a new cost-effective data acquisition system using open-source hardware and Mat-

lab/Simulink. The proposed data acquisition (DAQ) system has features that it uses the framed data protocol

based on hex encoding, it can acquire multiple data which are not of the same type at different sample rates,

and the system receives data through USB communication or serial communication. The software of the pro-

posed system consists of the ﬁrmware of a microcontroller and user-deﬁned Simulink function block. The

ﬁrmware of a microcontroller is in the form of a header ﬁle, and the data acquisition can be easily achieved

by calling a few functions deﬁned in the header ﬁle. The developed user-deﬁned Simulink block can get

multiple data at different sample rates by conﬁguring the GUI parameters appropriately. For implementation

of the system, we use the Arch Max, which is the open-source hardware with an ARM Cortex-M4 core, and

also use a user-deﬁned c-code S-function of Matlab/Simulink. For the demonstration of the superiority of the

implemented system, we compare the proposed system’s performance with that of the data acquisition system

provided in Matlab/Simulink Instrument Control Toolbox. Finally we illustrate how presented system can be

actually used by applying the proposed system to DC motor control.

1 INTRODUCTION

In the control system, it is very important to acquire

data via device for designing system, maintenance

and performance veriﬁcation, etc. The device which

acquires the data is called the data acquisition(DAQ)

system.

The DAQ device consists of a hardware and a soft-

ware. The hardware is connected to the target through

sensors, at the same time, connected to a PC for the

communication. One of the method to communicate

with a PC was proposed through the special equip-

ment for the high frequency sampling(Pereira et al.,

2008)(Khan et al., 2011). We need the dedicated soft-

ware for the DAQ device (Mandal et al., 2015). In

addition, serial communication was also used for the

data transmission. But in this case, the high sampling

rate is limited because of the bandwidth of serial com-

munication. So the USB DAQ board was proposed to

upgrade the data transmission speed(ABU HASAN,

2012)(Profﬁtt et al., 2006)(Stankovi´c et al., 2012).

A DAQ software transmits the data from the DAQ

device to the PC in form of the protocol. The PC soft-

ware is designed for the dedicated DAQ device, or use

the existing software(Salami et al., 2011)(Lee et al.,

2012). One of the existing software, Matlab/Simulink

provides Instrument Control Toolbox or Data Acqui-

sition Toolbox which help to communicate with the

external device through the TCP/IP or serial commu-

nication(MathWorks, 2009)(Storey, 2002).

The monitoring system that uses the function of

the DAQ device displays the acquired data through

the plotting function of a software in real time. Users

can observe the acquired data graphically through the

monitoring system. So the monitoring system is help-

ful to the user, because it gives the insight about the

system.

The open-source hardware is that design resources

of the product to make the same function and form

are freely provided by copyright holder. Even some-

body make the copy product for a commercial use,

the copyright holder doesn’t get the royalty. If peo-

ple who make the copy product express the copy-

right, they can freely modify and redistribute the de-

sign resources. In this reason, the open-source hard-

ware is already used in commercial purposes, the ed-

ucation and research area(Pearce et al., 2012)(Pearce,

2015)(Claros-Marﬁl et al., 2016).

Some open-source hardware microcontroller

board have built in USB. If the open-source hardware

484

Seo, S., Park, Y. and Lee, Y.

Development of a Cost-effective Data Acquisition System using an Open-source Hardware and Matlab/Simulink.

DOI: 10.5220/0005978004840491

In Proceedings of the 13th International Conference on Informatics in Control, Automation and Robotics (ICINCO 2016) - Volume 1, pages 484-491

ISBN: 978-989-758-198-4

microcontroller board can communicate data with

Matlab/Simulink, the cost-effective DAQ system

can be developed which uses USB communication.

Also, the development processes will be very easy

because of open-source hardware’s characteristics.

If we conﬁgure the DAQ system which uses the

open-source hardware microcontroller board, then

it can acquire the data with a valid sampling rate in

the simple theoretical research veriﬁcation and the

engineering education. Aspect of convenience, it has

a portability and can be easy installed because of

USB’s plug and play characteristic. If the ﬁrmware

of device has a high portability, this DAQ system can

be programmed with a controller. So, the user can

acquire the state values of the controlled system.

This paper proposes a new cost-effective data

acquisition system using open-source hardware and

Matlab/Simulink. We propose the algorithm includ-

ing the protocol, and implement the DAQ device

ﬁrmware and user-deﬁned Simulink block adapting

the proposed algorithm. We compare the proposed

system’s performance with that of the data acquisi-

tion system provided in Matlab/Simulink Instrument

Control Toolbox. In addition, we experiment the pro-

posed system by applying it to DC motor control.

2 STRUCTURE OF SYSTEM

The proposed DAQ system uses the open-source hard-

ware microcontroller board that can use serial com-

munication or USB communication, and communi-

cates the acquired data with user-deﬁned Simulink

block. The concept of system is Figure 1. In the DAQ

system, the microcontroller board sends the acquired

data to PC through unidirectional communication. An

ideal DAQ system should have no data missing, can

acquire multiple data which are not of the same type

at different sample rates. The proposed system com-

PC (Simulink user defined function)

Model initialize()

Model Start()

Model Output()

Model Terminate()

Simulink

Engine

End Simulation

HW initialization

HW loop

Task except

data transmission

u- controller

Periodic loop

Figure 1: The conceptual diagram of the proposed DAQ

system.

bines the acquired data and the next data with the in-

formation of the data type and the channel number by

using separator, and sends it to PC. Through this pro-

cess, the distinction of the series data become clear,

access time of the DAQ device to a PC decreases, and

the DAQ system can transmit the acquired data with-

out missing. Therefore, the DAQ system should sat-

isfy the following conditions.

1. The DAQ system can acquire multiple data at

different sample rates.

2. All the channels should be able to have another

type of data.

3. There is no need to match the sampling time

and the data transmission interval.

4. The block returns the data corresponding to

sampling each a period of sampling.

5. Receiving and converting data is executed at

least in Simulink.

For this conditions, we proposefollowingprotocol

and the method that generates a data packet and the

algorithm for receiving data, and implement the DAQ

block using user-deﬁned Simulink block.

2.1 Protocol

In protocol conﬁguration, the protocol including en-

coding changes the raw data and lengthens the to-

tal length of data, and increases the data transmis-

sion load. But, we can use some values that are not

appeared after encoding as a control command, and

the control commands make clear the data transmis-

sion. The proposed protocol is based on hex encod-

ing, and is represented in Figure 2(a). The sensed data

are changed through hex encoding and reconstructed

by adding the information of the data type and the

channel number. In hex encoding, the encoded data

are represented only as a hexadecimal number, other

numbers can be used to command. We use the ’T’,

’Q’ as the control command by inserting the ’T’, ’Q

in the front and rear of the encoded data. The ’T’,’Q’

which are used as a separator separate the data that

are sampled at different time like Figure 2(b). We add

a ’Z’ at the end of the combined the data as a termi-

nator, and use it as a data packet. If the data packet

is transmitted, as shown in Figure 3, each data can

be distinguished by the acquired sampling time us-

ing the ’T’ and ’Q’. The data between ’T’ and ’Q’

have the information about type and channel, even

some channel data are not sampled at speciﬁc sam-

pling time, the receiving part know which data are

transmitted and are not transmitted. If these functions

can be implemented as user-deﬁned Simulink block,

system doesn’t have problem from different sampling

time.

Development of a Cost-effective Data Acquisition System using an Open-source Hardware and Matlab/Simulink

485

Info.

Data k

Hex

Data k

MSB 4 bit

type of data

LSB 4 bit

number of data

Hex encoded data

k-th channel data

...

......

...

Hex encoding

& framing data

...

(a)

T1 data

Q T Q T

Tn data

Q Z

...

(b)

Figure 2: (a) : Hex encoding and data framing, (b) : Data

packet.

1st channel

data 1

2nd channel

data 1

3rd channel

data 1

1st channel

data 2

3rd channel

data 2

1st channel

data 3

2nd channel

data 2

3rd channel

data 3

1st channel

data 4

3rd channel

data 4

Q Z

T1 data

1st channel

data 1

2nd channel

data 1

3rd channel

data 1

1st channel

data 2

3rd channel

data 2

1st channel

data 3

2nd channel

data 2

3rd channel

data 3

1st channel

data 4

3rd channel

data 4

T2 data

T3 data

T4 data

Get new packet from device

Figure 3: Decoding of a data packet.

2.2 DAQ Device Firmware

Generally, a DAQ system can be used through the

simple GUI format. However, the proposed system

dose not target a speciﬁc microcontroller, it is hard to

develop the system that only uses GUI format. So, for

simplifying implementation of the system, we con-

ﬁgure the DAQ device ﬁrmware as a header ﬁle for-

mat. Figure 4 represents overview of the ﬁrmware.

At start, the DAQ device connects acquired data vari-

ables and the information of the channel number and

the data type using the deﬁned function in header ﬁle.

After the loop beginning, the DAQ device calls the

function for updating ﬂags that represent new data

are sensed. When every data are updated, the device

calls another function for making the data packet and

sending packet to PC. As with the previous process, if

ﬁrmware is conﬁgured in the header ﬁle format for the

function declaration and the data transmission, we can

implement the DAQ system without the consideration

of hardware and protocol in the stage of use. The user

can use the system by programming like Figure 5.

u- controller firmware

connectData(1,unsigned int,data_1);

connectData(2,float ,data_2);

connectData(n,double,data_n);

SetBit(UpdateDoneFlag,1);

SetBit(UpdataDoneFlag,2);

SetBit(UpdataDoneFlag,n);

ProcessToHostBlock();

...

Initialize()

.........

loop()

connectData(channel,data_type,data_name);

SetBit(UpdateDoneFlag,channel_num);

ProcessToHostBlock();

Data transmission header file

Figure 4: The overview of ﬁrmware.

2.3 Algorithm for Block

Implementation

Figure 6 represents the ﬂowchart of each user-deﬁned

Simulink block. The algorithm of the block is sat-

isfying previous conditions. First branch uses the

StartFlag that is used for checking the ﬁrst loop of

system as a condition of branching, this case is exe-

cuted only once for the data acquiring process. If the

StartFlag is true, communication initializing function

is run for receiving the data from the device and the

StartFlag becomes false. Second branch is used to

check block’s process operating number and the re-

maining data to decoding through the OrderIndex and

the NoDataFlag. The OrderIndex is execution num-

ber of block in Simulink, and The NoDataFlag is true

when non-decoded data packet is not exist. When the

NoDataFlag is true and OrderIndex is zero, second

ICINCO 2016 - 13th International Conference on Informatics in Control, Automation and Robotics

486

(a)

(b)

Figure 5: Examples of actual use( (a) : initialize, (b) : loop).

branch goes to yes, and block receive the packet like

Figure 2(b) from buffer. Before the received packet

are entirely decoded, the NoDataFlag is false every

loop, so second branch goes to no. Third branch goes

to yes when the block’s OrderIndex is zero. If third

branch goes to yes, the part of the data packet is de-

coded. At the end of the ﬂowchart, the decoded data

are came out from the block refer to the channel num-

ber step by step. By the previous process, the system

can minimize the number of data receiving and decod-

ing. Because the data packet can be separated using

the ’T’ and ’Q’ like Figure 3, the algorithm can be

implement corresponding to the previous conditions.

Generating and transmitting data packet make delay

between the target system and the acquired data, but

reduce the load from device access.

2.4 Implementation of Communication

Block

We conﬁgure the communication block using the pro-

posed algorithm, communication protocol and Mat-

lab/Simulink c-code S-function. Simulink determines

priority number of every block that consist of model

according to deﬁned rule, and the individual block’s

initialization and output calculation is executed in ac-

cordance with the priority. In consideration of the

characteristics of Simulink, the method considering

the priority should be included. For making user-

deﬁned Simulink block, we use provided the format

about input-output size, sampling time etc, and im-

Start

StartFlag == true

InitCommunic ation()

StartFlag == false

OrderIndx == 0 &

NoDataFlag == true

Data acquisition

from u- controller

& Put data into buffer

NoDataFlag = false

OrderIndx == 0

Data decoding from buffer

Make every channel data

Update data

refer to channel number

Return

Yes

Data packet

Figure 6: The ﬂowchart of the user deﬁned block.

plement block including the method that can receive

channel number and sampling time. We conﬁgure

the block that can be connected with the USB device

driver through the function that OS provides. Also,

like Figure 7, we make the function parameter that

can be easily changed using GUI.

3 PERFORMANCE TEST

We compare the performance of proposed sys-

tem with that of DAQ system provided in Mat-

lab/Simulink Instrument Control Toolbox. We used

an open-source hardware Arch Max as a DAQ unit

for the test. The Arch Max has the features that it is

supported by mbed project based on ARM and open-

source project, the user of the Arch Max can use free

development tool via the internet, and it support drag

and drop programming. The Arch Max use the mi-

Development of a Cost-effective Data Acquisition System using an Open-source Hardware and Matlab/Simulink

487

Figure 7: The implemented block and block’s GUI.

crocontroller STM32F407 that is ARM Cortex-M4,

32bit,and 168MHz maximum clock speed and sup-

port USB full speed and USB High speed. In this test,

we set clock speed 168MHz and use USB full speed

using CDC class.

Figure 8: The open-source hardware Arch Max(ARM

STM32F407).

3.1 Compare Data Packet Generation

As shown in Figure 9, the DAQ system consists of

serial communication block in the Matlab/Simulink

Instrument Control Toolbox. This system uses the

binary data transmission protocol adding terminator,

and some settings can be changed via the GUI. And

Figure 9: The DAQ system using the Matlab/Simulink In-

strument Control Toolbox.

the other system that we proposed uses the protocol

as shown in Figure 3.

We check the load of the packet generation and

transmission through measuring the time taken. If

the time taken of the packet generation gets longer,

it will have implications on the performance of the

DAQ system. Figure 10 shows the time taken that

changes from 5 ﬂoating point data to the data packet

and transmits. If we ignore the GPIO toggling time,

we can measure the time taken using the GPIO toggle

back and forth of the packet generation and transmis-

sion. In the binary data transmission case, it takes

about 1 micro-second. In the presented protocol case,

periodically, the time taken appears longer than oth-

ers because the system collects several sampled data

and periodically changes from the acquired data to the

packet. So, we measure the longest time and that is

about 8 micro-second. If we use a 1kHz sampling

rate, the time taken of both cases are not over 1% of

the available time. So the packet generation problems

are hardly happen.

3.2 DAQ Performance Test

Figure 11 represents the result of receiving 5 ﬂoat-

ing point data about 100Hz sampling and 1000Hz

sampling through Matlab/Simulink Instrument Con-

trol Toolbox. The results have data missing, and re-

sult of 100Hz sampling frequency shows indentation

because of low sampling frequency. The result of

1000Hz sampling frequency has better smoothness

than previous case, but it’s data missing is longer

than the previous. Figure 12 is the results of receiv-

ing 5 ﬂoating point data using proposed system about

1000Hz sampling and 5000Hz sampling. The ex-

periment results doesn’t have the data missing both

1000Hz sampling and 5000Hz sampling. Depending

on the experiment results, the proposed system has

more better data acquisition ability than that of Mat-

lab/Simulink Instrument Control Toolbox.

Figure 13 is the visualized data drop. The method

which measures the data drop is sending the inte-

ger data that is increased 1 per sampling with other

data and checks the difference of adjacent two num-

bers. If the difference is n, then n− 1 sampled data

are dropped. In Figure 13, the case that uses Mat-

lab/Simulink library shows 242 data drop when block

receive data 1kHz. This means 242 data drop per

1.242 second, so the data drop rate is about 19.5%. In

contrast, the result of the proposed system shows no

data drop even sampling frequency is 10 times faster.

In repeated experiments, about 20% data drop happen

when Matlab/Simulink library is used, and data drop

doesn’t happen when the presented system is used.

ICINCO 2016 - 13th International Conference on Informatics in Control, Automation and Robotics

488

(a) Binary data transmission packet case.

(b) User-deﬁned data transmission packet case.

Figure 10: Time taken to generate a packet of 5 ﬂoating

point data.

3.3 Actual DAQ System Test with DC

Motor Velocity Control

Figure 14 represents the conﬁguration of DC motor

experimental system for the practical application of

the proposed system. The experimental system con-

sists of the DC motor, the encoder board, the motor

driver board and the Arch Max with the Arch Max

adaptation board.

The experiment is to control the angular velocity

of DC motor in no-load condition. We conﬁgure the

PI controller. In the experiment, we give the sinu-

soidal reference to system, sample angular velocity

1000Hz sampling frequency and conﬁgure the feed-

back loop. At the same time, we conﬁgure the mon-

itoring system using Matlab/Simulink scope block.

With reference to the plot in Figure 15, the user can

easily design the PI controller by changing the coefﬁ-

cients.

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

−1

DAQ result of 5 sinusoidal signals (100Hz)

time

Amp(offset : 0, 2, 4, 6, 8)

(a)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

−1

DAQ result of 5 sinusoidal signals (1000Hz)

time

Amp(offset : 0, 2, 4, 6, 8)

(b)

Figure 11: The result of the Simulink library block( (a) :

100Hz sampling, (b) : 1000Hz sampling).

4 CONCLUSIONS

In this paper, we proposed a new cost-effective data

acquisition system using open-source hardware and

Matlab/Simulink. The proposed DAQ system has the

following features : it uses an open-source microcon-

troller board that supports USB communication or se-

rial communication, it is implemented for use with

Matlab/Simulink so that one can utilize all the con-

venient functions provided by Matlab/Simulink. To

implement the proposed system, we used an open-

source hardware Arch Max as a DAQ unit, developed

the device ﬁrmware and a DAQ block using user-

deﬁned c-code S-function. The ﬁrmware is in the

form of a header ﬁle, which includes several handy

functions. One can program the data acquisition by

calling the provided functions in a well deﬁned se-

quence. One can conﬁgure the developed Simulink

block so that he can obtain multiple data at differ-

ent rates by changing GUI parameters appropriately.

Throughthe experiment, we showed that the proposed

DAQ system has better performance than the system

provided by Matlab/Simulink. In addition to the ac-

quisition of sensor data, the proposed DAQ system

Development of a Cost-effective Data Acquisition System using an Open-source Hardware and Matlab/Simulink

489

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

−1

DAQ result of 5 sinusoidal signals (1000Hz)

time

Amp(offset : 0, 2, 4, 6, 8)

(a)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

−1

DAQ result of 5 sinusoidal signals (5000Hz)

time

Amp(offset : 0, 2, 4, 6, 8)

(b)

Figure 12: The result of the presented user deﬁned function

block( (a) : 1kHz sampling, (b) : 5kHz sampling).

0 0.2 0.4 0.6 0.8 1

0.5

1.5

time

drop rate check(1kHz, Matlab library block)

0 0.2 0.4 0.6 0.8 1

0.5

1.5

time

drop rate check(10kHz, User defined function block)

Figure 13: Visualized data drop.

Figure 14: The experiment setup of the DAQ system for DC

motor control.

0 1 2 3 4 5 6

−150

−100

−50

100

150

200

250

time

Kp = 0.1, Ki = 0

Ref. signal

velocity

0 1 2 3 4 5 6

−150

−100

−50

100

150

200

250

time

Kp = 0.1, Ki = 1

Ref. signal

velocity

0 1 2 3 4 5 6

−150

−100

−50

100

150

200

250

time

Kp = 0.1, Ki = 15

Ref. signal

velocity

Figure 15: Experiment results of DC motor PI velocity con-

trol(Top : Kp = 0.1 , Ki = 0 Middle : Kp = 0.1, Ki = 1

Bottom : Kp = 0.1, Ki = 15).

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490

can be used to monitor all the variables in the con-

trol algorithm. This allows the user to have better in-

sight in designing control system by providing plen-

tiful information. This aspect was clearly illustrated

by the controller design example. Since the proposed

system is based on open-source hardware, it is more

cost-effective than existing DAQ systems using PCIe

or expensive DAQ boards. The proposed system can

be successfully used for teaching purpose in under-

graduate or graduate courses.

ACKNOWLEDGEMENTS

This research was supported by the MSIP(Ministry

of Science, ICT and Future Planning), Korea, under

the ITRC(Information Technology Research Center)

support program (IITP-2016-H8601-16-1003) super-

vised by the IITP(Institute for Information & commu-

nications Technology Promotion)

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