ECE 4760 Final Project

NFC Transmitter and Receiver

Lingnan Liu (ll656) and Jilong Wu (jw859)

Introduction High Level Design Hardware Design Software Design Testing Strategy and Results Conclusion Appendices

Introduction

Our project is building one set of NFC module including a NFC transmitter and a NFC receiver both using ATmega1284p microcontroller. We will be using coupled coils to transmit message modulated by a high frequency carrier, whose frequency is the standard frequency for Near Field Communication (NFC) – 13.56MHz (Wikipedia, 2013).

In our project, we build a local oscillator which generates the accurate NFC carrier by using the crystal oscillator circuit. To set up the near field wireless transmission, we build two coupled coils as antennas to transmit and receive the message, which is the application of resonant inductive coupling. These two coils are tuned to resonate at the frequency of 13.56MHz. We use one ATmega1284p microcontroller to generate the message and modulate it with the carrier from our local oscillator. The modulated high-frequency signal will be transmitted through the coupled coils to the receiver including a transistor amplifier, a hysteresis comparator and another ATmega1284p microcontroller which processes the received signal and displays it through serial port.

As opposed to many colleagues who make complicated design with very dedicated application, we choose to dive into the working procedure of the wireless module and build it from scratch. The goal of our project is not a very detailed application, but a basic method of transmitting message through wireless channel which can be utilized by a large amount of applications. Through this project, we hope to make ourselves clearer about the working procedure of transmitting message at radio frequency and improve our practical skills.

High Level Design

Background

Near Field Communication (NFC) is a new technology that has emerged in the past decade. It is a set of standards for smartphones and similar devices to establish radio communication with each other by touching them together or bringing them into close proximity, usually no more than a few inches. This idea was originally used by radio-frequency identification, or RFID. RFID allows a reader to send radio waves to a passive electronic tag for identification, authentication and tracking. NFC, inherited from the working scheme of RFID, is only capable for a short range communicating and thus inherent secure data exchange can be applied. Many individuals and companies have seen the great potential of this new technology and thus many applications have been developed. For example, a company named Log-IC has used NFC tags to keep track of thermometer readings of temperature sensitive goods. Google also developed Google Wallet using mobile NFC. Currently, integration of NFC technology into mobile phones has been proved a practical solution. This creates a potentially huge market for NFC applications because nowadays almost everyone has a cellphone. All those novel NFC products are interesting and its promising future motivates us to figure out the pros and cons of this technology. Thus, we decided to build our own NFC module which can be used for extensive applications in the future.

Overview

In our design, we intended to use LC tank to work as antenna. Since the standard working frequency for NFC transmitter is 13.56MHz, the LC product is required to be very small. It turns out that the self-tuned inductor (coil) has the resonant frequency of 13.56MHz. We build our own 13.56MHz oscillator to work as the carrier frequency. The digital message from ATmega1284p is modulated by the carrier frequency and then transmitted through the wireless channel. Because of the loss during the transmission, the voltage of the received signal is not high enough to trigger comparator. To solve this problem, we build a unity-gain amplifier whose output is low voltage for input 1 with high frequency signal and high voltage for input zero. Then we use inverting comparator with hysteresis whose output signal is 5V for digital 1 and 0V for digital 0. Output from the amplifier is inverted after the comparator and hence the original digital message is restored. Then this restored digital signal is processed in ATmega1284 and the message is displayed through serial port.

Logical Structure

1. Hardware

The hardware of this project is composed of two main parts, transmitter and receiver. Transmitter block includes user interface (ATmega1284p), local oscillator (13.56MHz carrier generator) and antenna (LC Tank). Receiver block includes antenna, demodulation and ADC Circuit (unity gain amplifier and hysteresis comparator with inverting-input) and signal processing (ATmega1284p).

Figure 1 Components of NFC Module (Hardware)

2. Software

We will be using USART1 on ATmega1284p microcontroller to transmit and receive messages. To transmit a message, we first put it into a transmit buffer which will be sent through TX1 (PD3) one character at a time. For reception, hardware USART will automatically read bits from RX1 (PD2) and put it into UDR1 (USART Data Register). All we need to do is just read from this register and put it into a receive buffer which be further processed later.

3. Hardware and Software Tradeoff

The first tradeoff we have is the processing of the received signal. Since our transmission is achieved at a high frequency (13.56MHz), the loss during the transmission is relatively high. The voltage of received signal is quite low (around 300mV). Converting this low amplitude, high frequency signal into digital signal is really tricky. If the demodulation and ADC tasks are done by the microcontroller, more complex software processing method is required. This rapidly increases the computation burden of the microprocessor. However, if we use some hardware to share tasks of signal processing, the workload of the microprocessor will be reduced. Also, the signal is easily converted to desired digital signal by using our circuit implantation. Details about the implementation are described in the latter section.

4. Related Standards

In our project, the transmission frequency we use is 13.56MHz. It is within the band of 13.110 and 14.110 MHz. Thus, it is regulated by FCC 15.209 and FCC 15.229.

(a) The field strength of any emissions within the band 13.553-13.567 MHz shall not exceed 15,848 microvolts/meter at 30 meters.

(b) Within the bands 13.410-13.553 MHz and 13.567-13.710 MHz, the field strength of any emissions shall not exceed 334 microvolts/meter at 30 meters.

(c) Within the bands 13.110-13.410 MHz and 13.710-14.010 MHz the field strength of any emissions shall not exceed 106 microvolts/meter at 30 meters.

(d) The field strength of any emissions appearing outside of the 13.110-14.010 MHz band shall not exceed the general radiated emission limits in § 15.209.

(e) The frequency tolerance of the carrier signal shall be maintained within ±0.01% of the operating frequency over a temperature variation of −20 degrees to 50 degrees C at normal supply voltage, and for a variation in the primary supply voltage from 85% to 115% of the rated supply voltage at a temperature of 20 degrees C. For battery operated equipment, the equipment tests shall be performed using a new battery.

(f) In the case of radio frequency powered tags designed to operate with a device authorized under this section, the tag may be approved with the device or be considered as a separate device subject to its own authorization. Powered tags approved with a device under a single application shall be labeled with the same identification number as the device.

Table 1 FCC Regulations

Frequency(MHz)	Field Strength(microvolts/meter)	Measurement distance(meters)
0.009-0.490	2400/F/(kHz)	300
0.490-1.705	24000/F/(kHz)	30
1.707-30	30	30

Since our project is just building a prototype of NFC Module not for commercial use, the following standards are not required here (http://www.waazaa.org/download/), but for further application development, these standards must be taken into consideration.

Near Field Communication has a standard working frequency of 13.56MHz and for 13.56MHz air interface communication, ISO/IEC 18000-3 is required.

NFC standards cover communications protocols and data exchange formats, and are based on existing radio-frequency identification (RFID) standards including ISO/IEC 14443 and FeliCa. The standards include ISO/IEC 18092 and those defined by the NFC Forum, which was founded in 2004 by Nokia, Philips Semiconductors and Sony.

5. Existing Patent and Copyright

For our oscillator design, we used the design idea from the website of Home of the Z80 CPU. We modified the design to work at 13.56MHz for our project. Also, we modified the comparator design from Cornell University ECE4760 Lab4.We changed it into an inverting hysteresis comparator with different reference voltage.

Hardware Design

Coil Antenna

The antenna is built using two coils. The wireless transmission between these two blocks is done using resonant inductive coupling. A coil with oscillating current will generate an oscillating magnetic field. Other coil nearby will be driven by the oscillating magnetic field and hence signal will be transmitted.

Since our transmission is done at a high frequency, the parasitic capacitance takes a huge effect. A real coil can be approximately modeled as shown in Figure 2. Cp is the parasitic capacitance and R is resistance under DC voltage.

Figure 2 LC Tank Circuit

The resonant frequency given by this RLC model is . While, it is very hard to control the value of the parasitic capacitance (resistance can be ignored for long distance coil). The method we used here is measuring the self-resonant frequency of the coil and then adjust the size of the coil accordingly. After picking the coil with a certain inductance, we measure its self-resonant frequency. If this frequency is lower than 13.56MHz, we need to scale down the size of the coil. The inductance of a coil is given by the equation where D = coil diameter in inches, N = Number of turns, l = coil length in inches. So the inductance of the coil becomes smaller if we reduce the number of turns of the coil. Also, reducing the turns of the coil will decrease the parasitic capacitance as well since the parasitic capacitance is from the individual wire turn of the coil. If the picked coil has a self-resonant frequency higher than 13.56MHz, a capacitance () can be added in parallel with the coil to increase the resonant frequency. We assume the resonant frequency after adding is and for . By using this two sets of data we can find the value of L and Cp.(If you want to make it more precise, you can measure a third set of data to find value of R). For our own experience, after reducing the coil size for three times, we happened to get a coil with a approximate self-resonant frequency of 13.56MHz. One thing to mention here consider the transmitting efficiency will be affected by inductance. The maximum achievable efficiency is , where , , , , and are the Q facor of the transmitter and receiver coils. After some math, we can obtain approximately, If we deduce the inductance by cutting turns, which will make Q smaller and hence the efficiency will become lower.

Carrier Frequency Generation

Before a digital message being transmitted through wireless channel, it must be modulated to a higher frequency which is more suitable for wireless transmitting. ATmega1284 is running at a frequency 16MHz and its actual frequency upper bound is a lot lower. We cannot use MCU to generate a 13.56MHz signal so an oscillator is required. Our oscillator is a modified design from Home of the Z80 CPU, the schematic is shown in the red block in Figure 3. Basic idea to build an oscillator is an amplifier with a feedback network. In order for an oscillator to operate, two conditions must be satisfied: a. the loop power gain must be equal to unity; b. the loop phase shit must be equal to 0, 2pi, 4pi, etc. The exact frequency at which an oscillator will operate is dependent on the loop phase angle shifts within the oscillator circuit. The most common method to provide a stable net phase shift is to use a quartz crystal unit in the feedback loop. Figure 3 shows a depcition of the rectacne vs. frequency of a quartz crystal unit. As we can see from the plot, a quartz will have two frequencies of zero phase fs and fa. fs is referred as the series resonant frequeny and the higher one, fa, is reffered as the parallel frequency. At the seris resonant point, the resistnace is minimal and the current flow is maximal. At the prallel reonant point, the resistance is maximal and the current flow is minimal. Therefore, the parallel resonant frequency should never be used as the controlling frequency of an oscillator circuit. Thus, we choose a series reonsant osicllator cirucit design as shown in Figure 4. The two resitors are used to bias the invertor and the invertor will operate at its linear region. The resistor also provides a negative feedback to the invertor. The 100nF capacitor is used to block DC voltage. The 22pF capacitor is used to bias the crystal at high frequecny. We choose these values so that the series resonant oscialltor will operate at the natural frequency of the crystal, which is 13.56MHz.

Figure 3 Reactance vs. Frequency Plot of a Quartz Crystal Unit

Digital Modulation (On-off Keying)

We used On-off keying (OOK) for our digital modulation. It is the simplest form of amplitude-shift keying modulation (ASK) that represents digital data as the presence or absence of a carrier wave (Wikipedia). The presence of a carrier for a specific duration represents a binary one while its absence for the same duration represents a binary zero. OOK is easier to implement and more spectrally efficient than other modulation scheme. Thus, we pick this method for our digital modulation.

The signal out of OOK modulation can be expressed in the form:

where is the modulated signal, is the digital signal to be modulated and is the carrier.

For circuit implementation, as shown in Figure 3, message is converted into digital high/low voltage signal by the microcontroller. The digital signal and carrier frequency (13.56MHz) are combined together. It will be a high frequency signal for binary 1 while absence of this signal for binary zero.

Figure 4 Transmitter Schematic

Demodulation and Analog to Digital Conversion

The receiver schematic is shown in Figure 5. As discussed in the previous session, to couple the coil to work at a frequency of 13.56MHz, the inductance of the coil is quite small. This leads to low transmission efficiency. The amplitude of the received signal is only around 300mV. This signal is way too small and thus demodulated by an envelope detector seems not practical. We need to amplify this signal first.

However, another problem appeared. The received modulated signal has a high frequency with certain amplitude while almost zero amplitude when not sending message. After the amplifier, the high frequency will be amplified while the zero amplitude input will turned into high voltage (which is 5V for our project). If we continue to use a high pass filter, the amplitude will be abated again and still envelop detector will not work.

After some observation, we realized that since the purpose of this demodulation and ADC block is to restore the original digital signal from the received analog signal, we can process the signal after amplifier directly. If we design a unity-gain amplifier, the zero input will become high voltage after being inverted by the amplifier while the high-frequency, low amplitude part will have similar amplitude which is a low voltage output. In this way, output after amplifier will be high voltage for input low and low voltage for input high. The design of the unity-gain NPN amplifier is shown in in the orange block in Figure 5.

After signal is processed by the unity-gain amplifier, we use an inverting hysteresis comparator to convert it back to the signal which can be used directly as logic 1 and logic 0. Output from the amplifier will be fed into the inverting comparator. When input voltage is above , the comparator will output voltage low, which is 0V for our project. The output will not change until input voltage is blow . Then the comparator will output voltage low.

We set = 3.5 V and = 0.5V. After some math using equations: , we find and. The schematic of this inverting hysteresis comparator is shown in red block in Figure 4. The comparator converted analog input into digital output and this output will then be processed and analyzed by the microcontroller.

Figure 5 Receiver Schematic

Software Design

The responsibility of the driver software of our NFC module is divided into two parts. For the transmission part, the driver needs to accept the string that user want to transfer, form the data packet and send it through USART. For the reception part, the driver needs to read from the USART, write into receiver buffer and return the right string that user want to receive. We design our NFC communication library according to the standard C criteria, with NFCPack.h containing the declaration of functions and variables and NFCPack.c including their implementations.

Data Packet Format

Our data packet begins with a start token ‘#’, which reminds the receiver of the presence of valid data. Following parts are the transmitter id, data string (payload) and two checksums. One last character is the end token ‘%’, which indicates the end of valid data. The checksums are calculated only corresponding to the payload and are sent together with the data. It will serve as the reference checksum at the receiver side where the checksum will be calculated again and compared with the reference to eliminate possible transmission error.

This data packet format is inspired by the packet format we have been using through the infrared communication lab. We think this format can protect the data from being interfered and retain its integrity as most as possible. The disadvantage of this data packet is that the start token and end token cannot be used in the payload as this will break the data packet and mislead the receiver. However, this problem can be resolve simply by using different unprintable characters as the start token and end token.

Timer 0 Interrupt and USART1

We use USART1 on ATmega1284p microcontroller as the transmitter port and receiver port. Baud rate setting is in NFCPack.h. For now, we can sustain 19200 baud with no transmission error, which is a very high baud rate compared to the infrared communication system.

The Timer/Counter 0 is set to CTC mode and serves as a 1ms time base. Every 1 millisecond, the interrupt service routine will send and receive a character through USART1.

Important Library Functions and Macros

1. NFC_UART_BAUD: Baud rate setting macro

By redefining this macro, the baud rate of NFC communication can be changed. Now the highest baud rate we sustain is 19200 baud.

2. nfc_send_packet: Transmit a string

Its prototype is

void nfc_send_packet(char tx_id, char data[]);

This function is used to send the string stored in data[]. A transmitter id must be provided as the first argument of this function. This function will be blocked until every character in the string is sent so DON’T use it in timer interrupt service routine.

3. nfc_rec_packet: Receive a string

Its prototype is char nfc_rec_packet(char tx_id, char data[]);

This function is used to receive a data string and store it into data[]. A transmitter id must be provided as the first argument of this function. This function will use the transmitter id as reference and only receive the data packet that has the particular transmitter id. A number will be returned indicating the status of the transmission: 0 means good data, 1 means buffer overrun, 2 means no data (time out), 3 means bad transmitter id, 4 means bad checksum.

Testing Strategy and Results

Hardware Test

As shown above, the main challenging point in our design is the hardware part. Thus, we also pursue our most test effort in hardware side. Following the incremental design and unit test strategy, the hardware testing for this project is divided into two phases:

Phase 1: we individually test the functionality of every block

We first provided DC voltage for oscillator and checked the frequency of the output signal at the static state. We adjust the size of the capacitor to make it oscillate at a frequency around 13.56MHz, which serves as the carrier frequency. Then we modulate that carrier frequency with the message to be transmitted, which is compared with the original digital message to check if the modulated signal is what we want. The carrier waveform is shown in Figure 5 and the modulated signal is shown in Figure 7.

To test the functionality of the coil antenna, we use a function generator to generate a 13.56MHz signal which is feed to the transmitter end and check the received signal on the receiver end to see if signal can be transmitted and large enough. This test should pass easily since we have already used this method to test when we adjust the size of the coil. The received signal at the receiver end is shown in Figure 8.

Phase 2: we connect all the blocks together and test the whole system

We pursue the whole system test only after the unit test of every individual module have passed, eliminating the chance that one glitch in one block ruins the whole system. We connect the blocks together to form the whole NFC transmitter/receiver and measure the waveform of every relevant point in circuit to test the functionality of the whole system. In this phase, we measure the waveform of the amplified received signal and the signal after comparator, shown in Figure 9 and 10.

Figure 6 Carrier Wave around 13.56MHz

Figure 7 Modulated Signal

Figure 8 Received Signal

Figure 9 Amplified Signal

Figure 10 Restored Signal (After Comparator)

Note that the upper signal in Figure 7, 8, 9 and 10 is the original message from the transmitter. Comparing it with the signal we process, we can see that our circuit does work as intended: transmitting the message and receiving it with no distortion.

Software Test

The test of our software (aka. the driver to implement the data package format and the NFC communication library) is also very important. We write a simple C program named NFCTest.c to test the functionality of our NFC communication library.

NFCTest.c utilizes Tiny Real Time multitasking kernel to implement the transmitter task and the receiver task. These two tasks act like state machines whose state transition diagrams are shown in Figure 11 and 12.

Figure 11 State Transition of Transmitter Task

Figure 12 State Transition of Receiver Task

Transmitter task will wait in IDLE state until new message from serial port input by us comes in. Then it will turn to SEND state and transmit the new message using our library function: nfc_send_packet(). Once the transmitting is finished, transmitter task will return to IDLE state waiting for the next message.

Receiver task tries to receive the packet in RECV state. Once the packet is valid, it turns to DISP state to display the payload through the serial port. Then it returns to RECV state waiting for the new data packet.

Through the test, we find that our NFC communication library functions normally as intended.

Results

The picture of the NFC transmitter and receiver we built are shown in Figure 13 and 14.

Figure 13 Transmitter Hardware (without MCU)

Figure 14 Receiver Hardware (with MCU)

The performance metrics of our design is shown in Table 2.

Table 2 Comparison between Our Design and Other Similar Technology

	Our Design	Common NFC Reader
Working Frequency	13.56MHz	13.56MHz
Response Time	0.1s	<0.5s
Baud Rate	19200	Very high
Range	2cm	<10cm
Cost	$51*	~$50

Note that the cost for our project is around $51. This cost is calculated using ATmega1284p. However, if this module can be scaled down to PC board and embedded into mobile cellphone, the cost for MCU will be excluded.

As shown in the performance metrics, our design has similar performance as general NFC reader in market nowadays. However, what we have done is based on lab facilities from class and it is a rough design. More improvements can be performed and better performance (smaller size, faster response time, lower cost, etc) is achievable.

For further improvements, we will first scale down the device size of the system. Printed PCB boards will be designed and manufactured. Also, we will use TR package for ATmega1284p. This package will have smaller size and lower cost.

For applications, many ideas can be applied using this NFC module:

-Home Auto Switch

We can use NFC module as switches to control Wi-Fi, Bluetooth and turn up or down the volume of stereo system at home. Whenever we left home, we can just put our phone close to a NFC tag and turn off the Wi-Fi or Bluetooth in a convenient way.

-Business Card in Wallet

NFC Module can be used to read information from a NFC tag in a wallet. This tag can store any information like name and job. This tag will work as an electronic business card. As long as a NFC reader is close to the tag, the information can be read and analyzed.

-Locking Door

NFC Module can built to lock or unlock our door. The microcontroller built inside the NFC module can used to control mechanical lock system. As more and more smartphone will have a NFC module in it, you can just wave your cellphone towards the door and you can lock or unlock the door within a very short time.

-Business Advertisement

We can print out NFC tags to advertise our own business. When someone sees the NFC tag, they can use their cellphone to scan it and it will show the location of our business on google map. It is much faster than QR code. The response time for the NFC reader in market is less than 0.5s.

Conclusion

Summary

In the final project, we manage to build our own NFC module consisting of NFC transmitter and receiver. The module is able to work properly at the frequency of 13.56MHz with 0.01% error rate and a working range of 2cm. The cost is $51, within the budget. What we will do differently next time is to develop more useful applications for this project based the module. Several interesting ideas have been discussed in the Results section. Also, if we do it differently next time, we will use a high gain amplifier and an envelope detector to demodulate the signal instead of one unity-gain amplifier. We will compare the performance of these two system in terms of response time, maximum baud rate, error rate, etc.

As discussed in Results, our NFC module has similar performance metric as common NFC Reader in market. Also, it follows FCC regulations as discussed in Legal Considerations. If this module is developed for other applications including commercial uses, many other standards from RFID regulations and NFC forum must be taken into consideration.

Intellectual Property Considerations

The code we used for our design is originally written by our team for ATmega1284p. For hardware design, we used the oscillator design idea from the website of Home of the Z80 CPU. We modified the design to work at 13.56MHz for our project. Also, we modified the comparator design from Cornell University ECE4760 Lab4.We changed it to an inverting hysteresis comparator with different reference voltage.

Ethical Considerations

Our project strictly follows IEEE Code of Ethics. As discussed in the previous part, our design is a prototype for NFC applications. These applications include smart lock, temperature tag, etc. People will benefit a lot from these applications of NFC. These applications will keep the safety, health and welfare of the public. Meanwhile, it will keep any harm that may cause danger to them. We tested our design by measuring signals from different blocks using oscilloscope. We summarized our results based on the real data from measurement. We don’t accept any form of briberies. In the background and results section, we discussed many applications that can be used based on our NFC module and as mentioned in Conclusion, we will transform this design into print board which has smaller size and more stable performance. We also have talked about the limitations of our design. We are open to any form of criticism and suggestions regardless of race, religion, gender, disability, age or national origin. All the design is done carefully and thoughtfully to avoid injuring others or infringe upon other people’s reputation, property, etc. Both our team members assist each other to solve technical problems and also learn to follow IEEE Code of Ethics.

Here we would like give special thanks to our instructor Bruce Land and TAs who gave us tremendous instructions to improve our design not only in class, but also during lab work. We also would like to thank website Home of the Z80 CPU which gives us the idea for our basic design.

Legal Considerations

In our project, the transmission frequency we use is 13.56MHz which is regulated by FCC 15.209 and FCC 15.229. We fulfilled all the requirements.

The field strength of any emissions within the band 13.553-13.567 MHz shall not exceed 15,848 microvolts/meter at 30 meters. Since our transmission has a very short range of 2cm, the field strength is very small at 30 meters. Thus, this requirement will be satisfied for the NFC module we built.

Within the bands 13.410-13.553 MHz and 13.567-13.710 MHz, the field strength of any emissions shall not exceed 334 microvolts/meter at 30 meters. This is not required for operating frequency of 13.56MHz.

Within the bands 13.110-13.410 MHz and 13.710-14.010 MHz the field strength of any emissions shall not exceed 106 microvolts/meter at 30 meters. This is not required for operating frequency of 13.56MHz.

The field strength of any emissions appearing outside of the 13.110-14.010 MHz band shall not exceed the general radiated emission limits in § 15.209. This is not required for operating frequency of 13.56MHz.

The frequency tolerance of the carrier signal shall be maintained within ±0.01% of the operating frequency over a temperature variation of −20 degrees to 50 degrees C at normal supply voltage, and for a variation in the primary supply voltage from 85% to 115% of the rated supply voltage at a temperature of 20 degrees C. For a temperature of 20 degree C, we changed the supply voltage within the range of 85% to 115% of the rated voltage, the frequency changes within 13.48MHz to 13.60MHz which is within ±0.01% of 13.56MHz. Also, due to limitations of testing equipment, we are not able to test it over a temperature variation of -20 degrees to 50 degrees C at normal supply voltage. But for further development of this product, the temperature test will be conducted in high priority.

In the case of radio frequency powered tags designed to operate with a device authorized under this section, the tag may be approved with the device or be considered as a separate device subject to its own authorization. Powered tags approved with a device under a single application shall be labeled with the same identification number as the device. Since we are not building radio frequency powered tags in our project, we don’t need to worry about this regulation.

Table 3 FCC Regulations (FCC 15.209)

Frequency(MHz)	Field Strength(microvolts/meter)	Measurement distance(meters)
0.009-0.490	2400/F/(kHz)	300
0.490-1.705	24000/F/(kHz)	30
1.707-30	30	30

As discussed in the first part, since our project is just building a prototype of NFC Module and not for commercial use, standards ISO/IEC 1800, 0-3, ISO/IEC 18092, ISO/IEC 14443 and FeliCa and those defined by the NFC Forum are not required here, but for further application development, these standards must be taken into consideration.

Appendix A Relevant Source Code

1. NFCPack.h: The declaration of the NFC communication library;

2. NFCPack.c: The implementation of the NFC communication library;

3. NFCTest.c: The test benchmark of the NFC communication library.

PCComm.h

Appendix B Hardware Schematic

Figure 15 NFC Module

Appendix C Cost Details

Table 4 Cost Details

Part	Description	Quantity	Unite Price	Total Price	Supplier
ATMega1284p	MCU	2	5	10	Bruce Land
DIP Socket	For MCU, NAND Gates, Op-amp	3	0.5	1.5	Bruce Land
Pin Header	Connections within each board and between different blocks	74	0.05	3.7	Bruce Land
NPN 2N3904	Unity-gain Amplifier	1	0.2	0.2	Bruce Land
Custom PC board	MCU board	2	4	8	Bruce Land
RS232 connector for custom PC board	Serial Connector for PC board	2	1	2	Bruce Land
LM358	Comparator	1	0.5	0.5	Bruce Land
MAX4233 for custom PC board	Serial Connector for PC board	2	7	14	Bruce Land
Solder Board	For transmitter and receiver board	4	2.5	10	Bruce Land
13.56MHz crystal	For oscillator design	1	0.56	0.56	Digikey
74LS00N	NAND gates for oscillator	1	0.67	0.67	Bruce Land
Total Cost				51.13