ACS ACR31 User Manual

ACR31 Swipe

Card Reader

Reference Manual V1.00

Subject to change without prior notice [e-mail]

www.acs.com.hk

Table of Contents

1.0. Introduction ............................................................................................................. 3

2.0. Features ................................................................................................................... 4

3.0. System Block Design .............................................................................................. 5

4.0. Hardware Design ..................................................................................................... 6

4.1. Battery .................................................................................................................................... 6

4.2. Audio Channel ....................................................................................................................... 6

4.2.1. Communication Parameters ......................................................................................... 6

4.3. Magnetic Stripe Card Interface .............................................................................................. 6

5.0. Communication Protocol ........................................................................................ 7

5.1. Audio Channel Message ........................................................................................................ 7

6.0. Commands ............................................................................................................... 8

6.1. SPH_to_RDR_Reset ............................................................................................................. 8

6.2. SPH_to_RDR_Sleep ............................................................................................................. 9

6.3. SPH_to_RDR_FirmwareVersion ......................................................................................... 10

6.4. SPH_to_RDR_GetStatus ..................................................................................................... 11

6.5. SPH_to_RDR_SetSleepTimeout ......................................................................................... 12

6.6. RDR_to_SPH_GetStatus ..................................................................................................... 13

6.7. RDR_to_SPH_FirmwareVersion ......................................................................................... 14

6.8. RDR_to_SPH_TrackData .................................................................................................... 15

6.9. RDR_to_SPH_ACK ............................................................................................................. 17

Appendix A. Track Data Error Code .............................................................................. 18

Appendix B. System Error Codes ................................................................................. 19

List of Figures

Figure 1 : System Block Diagram ........................................................................................................... 5

List of Tables

Table 1 : 3.5mm Audio Socket Wiring .................................................................................................... 6

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1.0. Introduction

The ACR31 Swipe Card Reader serves as an interface for the communication between a mobile
device and a magnetic stripe card. Different types of magnetic cards have different commands and
communication protocols, and the ACR31 establishes a uniform interface from the mobile device to
the magnetic card.

The ACR31 is connected to the mobile device through a 3.5-mm audio jack interface. Through this,
the ACR31 will read information from the magnetic cards through the decoder on the reader which will
be sent to the mobile device, such as a smartphone or tablet. Furthermore, as a way to enhance
security, the card information is encrypted using the AES-128 encryption algorithm before it will be
sent to the backend server.

This document describes the hardware and software design of the ACR31 and the list of commands it
uses to communicate with the mobile device.

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2.0. Features

• 3.5-mm Audio Jack Interface

• Powered by a CR2016 battery

• Reads up to two tracks of card data

• Capable of bi-directional reading

• Supports AES-128 encryption algorithm

• Magnetic Stripe Card Reader:

o Supports ISO 7810/7811 magnetic cards

o Supports Hi-coercivity and Low-coercivity magnetic cards

o Supports JIS1 and JIS2

• Supports Android™ 2.3 and above*

• Supports iOS 5.0 and above*

• Compliant with the following standards:

o CE

o FCC

o VCCI

o RoHS

o REACH

*Note: Visit www.acs.com.hk

for the list of supported devices.

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ACR31

Decoder IC

3.0. System Block Design

The system block design of ACR31 is depicted below:

Magnetic Head

Magnetic Stripe

ISO7810/7811

Power

Management

Audio Jack

Mobile Device

MCU

Battery

Figure 1: System Block Diagram

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4.0. Hardware Design

4.1. Battery

ACR31 is using a CR2016 battery which has a capacity of 90 mAh.

4.2. Audio Channel

4.2.1. Communication Parameters

ACR31 is connected to a mobile device through Audio Channel.

Pin Signal Function

1 Left Transmit the data to ACR31

2 Right Reset signal to ACR31

3 GND GND

4 MIC Transmit the data to smart phone

Table 1: 3.5mm Audio Socket Wiring

4.3. Magnetic Stripe Card Interface

ACR31 can read any magnetic stripe card that conforms to ISO 7810/7811 standards. ISO 7810
specifies the physical characteristics of the card, while ISO 7811 specifies the recording technique
used in identification cards.

High-coercivity (HiCo) magnetic stripes are typically black in color and are encoded with a stronger
magnetic field (2750 Oersted). This makes HiCo cards more durable because the data encoded on
the stripes are less likely to be unintentionally erased when exposed to an outside magnetic field.
When swiped across the magnetic head, HiCo magnetic stripes can induce larger signal pulses and
are more easily being detected and decoded.

Low-coercivity (LoCo) magnetic stripes are generally brown in color and are encoded with lower
magnetic field intensity (300 Oersted). They will induce small signal pulses compared to HiCo cards
when swiped across the magnetic head. As a result, the S/N (signal-to-noise) ratio is relatively low
and they are more vulnerable to noise interference. A more sophisticated hardware support and signal
processing algorithm are needed to decode the signal correctly.

Since the magnetic fields of HiCo and LoCo cards are different, a magnetic stripe decoder IC with
automatic gain control can be used in the design to cater these two types of cards.

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