Card transaction method based on field detection

Abstract

The invention discloses a field detection-based card transaction method, which is characterized in that in a card searching stage, a time sequence among various modes of a terminal is reasonably set, various card payment scenes are compatible, the problem that the current terminal needs to switch different card identification interfaces for transaction is solved, and the transaction efficiency is improved by combining a field detection mode of LPCD detection. According to the method for judging whether a transaction object is a non-contact entity card, the polling time of an NFC Tag mode of equipment is prolonged for a transaction scene of the non-entity card, the payment success rate of an electronic wallet and application payment selectable transaction scene is improved, a strategy of generating load change by the NFC Tag of a switch terminal is provided for the mobile electronic equipment in an LPCD mode continuously, and the payment success rate of the mobile electronic equipment is improved. And the electronic equipment is guided to be switched from the LPCD mode to the card reader mode, so that the success rate of jumping to the payment application by the electronic equipment is increased. And finally, a card searching result is timely returned to a transaction layer, and payment is smoothly completed.

Description

Technical Field

[0001] The present invention relates to the technical field of card payment, and in particular to a card transaction method based on field detection. Background Art

[0002] With the continuous development of payment technologies, card payment methods have evolved from the initial magnetic card payment to contactless payment. Subsequently, with the introduction of NFC (Near Field Communication) technology, non-contact payment has gradually emerged in the public eye, enhancing the convenience and security of transactions. Complying with the specified card protocols, major banks have promoted the non-contact card waving transaction method based on NFC technology. To simplify non-contact payment methods, various mobile phone manufacturers have developed e-wallets without physical cards using NFC technology, as well as touch-and-go payment terminal devices based on the NFC Tag mode.

[0003] The NFC Tag technology simulates the terminal device as a non-contact card of a T2T (Type 2 Tag) or T4T (Type 2 Tag). When the mobile electronic device approaches the terminal, it senses the load change, switches from the low-power LPCD detection field mode to the card reader mode, communicates with the device according to the card protocol, reads the link information in the Tag, and thus jumps to the specified application. The LPCD mode refers to the card finding mode of periodically switching on and off the non-contact field and sampling the field strength amplitude and phase changes in the surrounding environment to determine the presence of the card, while the card reader mode refers to the card finding mode of sending a card finding instruction according to the non-contact card protocol and waiting for the card to respond.

[0004] Although current payment terminals support all of the above card payment methods, an integrated identification method for all types of cards has not been proposed. When faced with different types of card payment scenarios, the terminal needs to frequently switch to different card identification interfaces, establish a connection with the payment card, and conduct subsequent transactions, which to a certain extent affects the merchant's usage experience. When there is an optional payment scenario for the e-wallet and payment application of the electronic device (i.e., the mobile phone user can choose between the mobile phone wallet or the payment application for transactions), the terminal only supports one payment method. Either switch to the card reader mode to lock the e-wallet of the electronic device for transactions, or simulate a Tag with application information for the electronic device to read and wake up the payment application for transactions. This obviously violates the principle of transaction method selectivity. Even if some terminal devices integrate the identification interfaces for e-wallets and payment applications, due to the inability to be compatible with the transaction methods of the Android system and the Ios system, the transaction success rate will be greatly reduced. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a card-based transaction method integrating non-contact, contact, magnetic card and NFC Tag technologies, so as to better adapt to the development of card-based payment methods and improve the user experience.

[0006] To achieve the above technical object, the technical solution adopted by the present invention is: a card-based transaction method based on field detection, including:

[0007] In the card searching stage, the terminal polls the NFC Tag mode, the card reader mode, the contact card recognition mode and the magnetic card recognition mode in sequence according to the set timing, so as to adapt to the mainstream card-based payment scenarios;

[0008] In the card reader mode, when the terminal recognizes a non-contact card, it switches to the NFC Tag mode;

[0009] In the NFC Tag mode, the terminal distinguishes non-contact physical cards and e-wallets based on the field detection function, and extends the polling time of this mode;

[0010] In the NFC Tag mode, the terminal distinguishes whether the current electronic device is continuously in the LPCD detection mode based on the field detection function. By switching the NFC Tag mode, the load changes are caused to guide the electronic device to switch from the LPCD detection mode to the card reader mode, and actively read the link content of the Tag.

[0011] In some embodiments, in the card searching stage, the terminal polls the NFC Tag mode, the card reader mode, the contact card recognition mode and the magnetic card recognition mode in sequence, adapts to the current mainstream card-based payment scenarios, sets the polling time of each mode, and switches to the NFC Tag mode when a non-contact card is recognized, realizes the selectable transaction scenarios of the e-wallet and payment applications of the mobile electronic device, and returns the card searching result to the transaction layer.

[0012] In some embodiments, when a non-contact card is recognized, the terminal switches to the NFC Tag mode;

[0013] In the NFC Tag mode, the terminal distinguishes non-contact physical cards and e-wallets based on the field detection function, returns the card searching result for non-contact physical cards, and for e-wallets, extends the polling time of the NFC Tag mode and waits for communication with the electronic device.

[0014] In some embodiments, when a non-contact card is recognized, the terminal switches to the NFC Tag mode;

[0015] In the NFC Tag mode, the terminal, based on the field detection function, differentiates between contactless physical cards and e-wallets. For e-wallets, it extends the polling time of the NFC Tag mode, waits for communication with the electronic device, and confirms whether the current electronic device remains in the LPCD mode. If it is still in the LPCD mode, it closes the NFC Tag mode and then turns it on after a delay, causing a load change to guide the electronic device to switch to the card reader mode.

[0016] In some embodiments, the card-based transaction method based on field detection specifically includes: a card search phase and a transaction phase;

[0017] In the card search phase, the terminal sequentially polls the NFC Tag mode, card reader mode, contact card recognition mode, and magnetic card recognition mode of the payment terminal within a specified time.

[0018] When the terminal switches to the NFC Tag mode and confirms that the link information in the Tag has been read, to implement the selectable transaction scenario of the mobile wallet and payment application, it switches to the card reader mode.

[0019] When the terminal switches to the card reading mode, it sends a card search instruction. When a contactless card is recognized, if the Tag information has been read, it directly returns the card search result; otherwise, the terminal switches back to the NFC Tag mode.

[0020] At this time, it is necessary to differentiate between contactless physical cards and e-wallets. According to the principle of the non-contact field emitted by the mobile electronic device, it detects whether the electronic device is in the LPCD mode or the card reader mode. If no field is detected from the device within the polling time, it directly returns the card search result of the contactless physical card; otherwise, it extends the polling time of the NFC Tag mode, and at the same time, the electronic device communicates with the terminal and a Tag is popped up. To improve the success rate of the device reading the Tag, if it is confirmed that the electronic device remains in the LPCD detection mode, the terminal will close the current NFC Tag mode and reopen it after a delay, causing a load change to guide the electronic device to switch to the card reader mode. When the terminal switches to the contact card recognition mode or the magnetic card recognition mode, when a contact card or magnetic card is inserted into the terminal, it exits the current polling mode and returns the card search result.

[0021] In the transaction phase, the terminal switches to the corresponding card-based interaction mode for transactions according to the card search result.

[0022] In some embodiments, according to the principle of the non-contact field emitted by the mobile electronic device, detecting whether the electronic device is in the LPCD mode or the card reader mode specifically includes the following steps:

[0023] The LPCD mode of the mobile electronic device adopts the strategy of periodically emitting a non-contact field. When a change in the environment is detected, it actively switches to the card reader mode and issues a card search instruction to confirm again whether the card is in place.

[0024] To determine whether the current electronic device is in the LPCD mode, after detecting that the electronic device emits a field, extend the time. If the non-contact field of the electronic device is detected to be closed at this time, confirm that the device is currently in the LPCD mode; otherwise, it is in the card reader mode.

[0025] In some embodiments, it is detected that the current electronic device is in the LPCD mode, and it is impossible to determine whether a change in the environment is detected and switched to the card reader mode before the next non-contact field is emitted. Therefore, before the terminal closes the NFC Tag mode, delay and detect whether the electronic device emits a non-contact field. If a field emission is detected, it is considered that the electronic device has switched to the card reader mode, and the NFC Tag mode is not selected to be closed; otherwise, it is considered that the device is still in the LPCD detection mode, and closing the Tag mode causes a load change, guiding the electronic device to switch to the card reader mode.

[0026] In some embodiments, during the card search stage, the terminal needs to sequentially poll the NFC Tag mode, non-contact card recognition mode, contact card recognition mode, and magnetic card recognition mode, and return the card search result to the transaction layer. The specific steps are as follows:

[0027] S1: Initialize the polling time and other related parameters of the NFC Tag mode;

[0028] S2: The device initializes and enables the NFC Tag mode;

[0029] S3: Determine whether the current time exceeds the set polling time. If yes, enter S4; if no, enter S31;

[0030] S31: Determine whether the transaction object has started, and distinguish between physical non-contact cards and non-physical non-contact cards. If yes, enter S311; if no, return to S3;

[0031] S311: Determine whether this start is an LPCD detection. If yes, enter S3111; if no, enter S312;

[0032] S3111: Clear the current time, the device closes the NFC Tag mode, delays and enables the Tag mode, and enters S312;

[0033] S312: Determine whether a non-contact card has been detected. If yes, enter 3121; if no, enter S313;

[0034] S3121: Extend the polling time of the NFC Tag mode and enter S313;

[0035] S313: Determine whether the current time exceeds the polling time of the NFC Tag mode. If yes, enter S3131; if no, enter S314;

[0036] S3131: Determine whether a contactless card has been detected. If yes, end directly; if no, enter S4;

[0037] S314: Determine whether the link information of the NFC Tag has been read. If yes, enter S3131; if no, enter S313;

[0038] S4: The device switches to the card reader mode, identifies the contactless card, and enters S5;

[0039] S5: Determine whether a contactless card has been identified. If yes, return to S2; if no, enter S6;

[0040] S6: The device switches to the contact card identification mode, identifies the contact card, and enters S7;

[0041] S7: Determine whether a contact card has been identified. If yes, end directly; if no, enter S8;

[0042] S8: The device switches to the magnetic card identification mode, identifies the magnetic card, and enters S9;

[0043] S9: Determine whether a magnetic card has been identified. If yes, end directly; if no, enter S2.

[0044] Adopting the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] 1. The present invention proposes a card-based transaction method based on field detection. During the card search phase, the terminal polls the NFC Tag mode, card reader mode, contact card identification mode, and magnetic card identification mode in sequence. This method can be compatible with the electronic wallet and payment application selectable transaction scenarios of mobile electronic devices with Android and IOS operating systems, and is applicable to various types of card payment scenarios, promptly returning the card search result to the application layer, unifying the current mainstream card payment means, and improving the user experience.

[0046] 2. The present invention proposes a reasonable mode switching situation. When the terminal is in the card reader mode and a contactless card is identified, and the link information in the Tag has not been read, it switches back to the NFC Tag mode. It realizes the scenario where the payment application can still be switched while the electronic wallet is popped up on the electronic device.

[0047] 3. The present invention distinguishes non-contact physical cards and e-wallets based on field detection, determines whether to extend the polling time of the terminal in the NFC Tag mode, and improves the success rate of the payment application that can be jumped when the e-wallet pops up on the electronic device without affecting the card search result return time of the non-contact physical card.

[0048] 4. The present invention confirms whether the mobile electronic device is continuously in the LPCD detection mode based on field detection, turns off the terminal NFC Tag mode and then turns it on again, causing a load change, and guides the electronic device to switch from the low-power LPCD mode to the card reader mode, improving the success rate of the payment application that the electronic device jumps to. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0050] Figure 1 It is a flowchart of the card transaction method;

[0051] Figure 2 It is a schematic diagram of the polling mode of each card search mode of the terminal;

[0052] Figure 3 It is a schematic diagram of distinguishing the LPCD mode and the card reader mode by the delay detection field;

[0053] Figure 4 It is a multi-mode card search flowchart. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The following will further describe the present invention in detail with reference to the drawings and embodiments. It should be specifically pointed out that the following embodiments are only used to illustrate the present invention, but do not limit the scope of the present invention. Similarly, the following embodiments are only partial embodiments of the present invention rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0055] The present invention provides a card transaction method based on field detection, including:

[0056] In the card searching stage, the terminal polls the NFC Tag mode, card reader mode, contact card recognition mode, and magnetic card recognition mode in sequence, adapts to the current mainstream card payment scenarios, sets the polling time for each mode, and switches to the NFC Tag mode when a contactless card is recognized, realizing selectable transaction scenarios for the electronic wallet and payment applications of the mobile electronic device, and returning the card search result to the transaction layer.

[0057] In the card reader mode, when the terminal recognizes a contactless card, the terminal switches to the NFC Tag mode;

[0058] In the NFC Tag mode, based on the field detection function, the terminal differentiates between contactless physical cards and electronic wallets, returns the card search result for contactless physical cards, and for electronic wallets, extends the polling time of the NFC Tag mode, waits for communication with the electronic device; and confirms whether the current electronic device remains in the LPCD mode. If it is still in the LPCD mode, the NFC Tag mode is turned off and then turned on after a delay, causing a load change to guide the electronic device to switch from the LPCD detection mode to the card reader mode and actively read the link content of the Tag.

[0059] Embodiment 1

[0060] As Figure 1 shown, this embodiment integrates a card transaction method that supports the recognition of contactless cards, contact cards, magnetic cards, and NFC Tag technology. This transaction method mainly includes a card searching stage and a transaction stage. In the card searching stage, according to Figure 2 shown, the terminal polls the NFC Tag mode, card reader mode, contact card recognition mode, and magnetic card recognition mode for the payment terminal in sequence within a specified time. When the terminal switches to the NFC Tag mode and confirms that the link information in the Tag is read, to realize the selectable transaction scenarios for the mobile wallet and payment applications, it is necessary to switch to the card reader mode.

[0061] When the terminal switches to the card reading mode, it sends a card seeking instruction. When a contactless card is recognized, if the Tag information has already been read, the card seeking result is directly returned. Otherwise, the terminal switches back to the NFC Tag mode. At this time, it is necessary to distinguish between the contactless physical card and the electronic wallet. According to the principle of the non-contact field emitted by the mobile electronic device, it is detected whether the electronic device is in the LPCD mode or the card reader mode. If no field emission from the device is detected within the polling time, the card seeking result of the contactless physical card is directly returned. Otherwise, the polling time of the NFC Tag mode is extended. At the same time, the electronic device communicates with the terminal and pops up the Tag. To improve the success rate of the device in reading the Tag, if it is confirmed that the electronic device is continuously in the LPCD detection mode, the terminal will close the current NFC Tag mode, and after a delay, reopen the NFC Tag mode to cause a load change and guide the electronic device to switch to the card reader mode. When the terminal switches to the contact card recognition mode or the magnetic card recognition mode, when a contact card or a magnetic card is detected to be inserted into the terminal, the current polling mode is exited and the card seeking result is returned. In the transaction stage, the terminal switches to the corresponding card interaction mode according to the card seeking result for transaction.

[0062] In this embodiment, the field detection methods for the LPCD and the card reader mode are specifically as follows: The LPCD mode of the mobile electronic device adopts the strategy of periodically emitting a non-contact field. When a change in the environment is detected, it actively switches to the card reader mode and sends a card seeking instruction to confirm again whether the card is in place. According to Figure 2 As shown, to determine whether the current electronic device is in the LPCD mode, after detecting the field emission of the electronic device, the time is extended. If the non-contact field of the electronic device is detected to be closed at this time, it is confirmed that the device is currently in the LPCD mode, otherwise it is in the card reader mode.

[0063] In this embodiment, even if it is detected that the current electronic device is in the LPCD mode, it is impossible to determine whether a change in the environment is detected and it switches to the card reader mode before the next non-contact field is emitted. Therefore, before the terminal closes the NFC Tag mode, it delays and detects whether the electronic device emits a non-contact field. If a field emission is detected, it is considered that the electronic device has switched to the card reader mode, and the NFC Tag mode is not selected to be closed. Otherwise, it is considered that the device is still in the LPCD detection mode, and closing the Tag mode causes a load change to guide the electronic device to switch to the card reader mode.

[0064] According to Figure 4 As shown, in this embodiment, the multi-mode card seeking process is as follows: In the card seeking stage, the terminal needs to sequentially poll the NFC Tag mode, the contactless card recognition mode, the contact card recognition mode, and the magnetic card recognition mode, and return the card seeking result to the transaction layer. Refer to Figure 4 As shown, the specific implementation steps are as follows:

[0065] S1: Initialize the polling time of the NFC Tag mode and other relevant parameters;

[0066] S2: Initialize the device and enable the NFC Tag mode;

[0067] S3: Determine whether the current time exceeds the set polling time. If yes, enter S4; if no, enter S31;

[0068] S31: Determine whether the transaction object is opened, differentiating between physical contactless cards and non - physical contactless cards. If yes, enter S311; if no, return to S3;

[0069] S311: Determine whether this opening is an LPCD detection. If yes, enter S3111; if no, enter S312;

[0070] S3111: Clear the current time, turn off the NFC Tag mode on the device, delay and then turn on the Tag mode, and enter S312;

[0071] S312: Determine whether a contactless card has been detected. If yes, enter 3121; if no, enter S313;

[0072] S3121: Extend the polling time of the NFC Tag mode and enter S313;

[0073] S313: Determine whether the current time exceeds the polling time of the NFC Tag mode. If yes, enter S3131; if no, enter S314;

[0074] S3131: Determine whether a contactless card has been detected. If yes, end directly; if no, enter S4;

[0075] S314: Determine whether the link information of the NFC Tag has been read. If yes, enter S3131; if no, enter S313;

[0076] S4: Switch the device mode to the card reader mode, identify the contactless card, and enter S5;

[0077] S5: Determine whether a contactless card has been identified. If yes, return to S2; if no, enter S6;

[0078] S6: Switch the device to the contact card identification mode, identify the contact card, and enter S7;

[0079] S7: Determine whether a contact card has been identified. If yes, end directly; if no, enter S8;

[0080] S8: Switch the device to the magnetic card identification mode, identify the magnetic card, and enter S9;

[0081] S9: Determine whether a magnetic card has been identified. If yes, end directly; if no, enter S2.

[0082] In summary, the present invention proposes a four-interface card transaction method integrating non-contact identification mode, contact identification mode, magnetic card identification mode, and NFC Tag technology. During the card search phase, the timing between different modes of the terminal is reasonably set to be compatible with various card payment scenarios, solving the problem that current terminals need to switch different card identification interfaces for transactions. Combining the field detection method of LPCD detection, a method for judging whether the transaction object is a non-contact physical card is provided. For the transaction scenario of non-physical cards, the polling time of the NFC Tag mode of the device is extended, improving the payment success rate of selectable transaction scenarios for e-wallets and application payments. When the mobile electronic device is continuously in the LPCD mode, a strategy of generating load changes by switching the NFC Tag of the terminal on and off is proposed to guide the electronic device to switch from the LPCD mode to the card reader mode, increasing the success rate of the electronic device jumping to the payment application. Finally, the card search result is returned to the transaction layer in a timely manner to complete the payment smoothly.

[0083] The above are only some embodiments of the present invention, and thus do not limit the protection scope of the present invention. Any equivalent device or equivalent process transformation made using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall similarly be included in the patent protection scope of the present invention.

Claims

1. A card-based transaction method based on field detection, characterized in that Including: In the card searching phase, the terminal polls the NFC Tag mode, the card reader mode, the contact card recognition mode, and the magnetic card recognition mode in sequence according to the set timing sequence, so as to adapt to the mainstream card payment scenarios; In the card reader mode, when the terminal recognizes a contactless card, it switches to the NFC Tag mode; In the NFC Tag mode, the terminal distinguishes between a contactless physical card and an electronic wallet based on the field detection function, and extends the polling time of this mode; In the NFC Tag mode, the terminal distinguishes whether the current electronic device is continuously in the LPCD detection mode based on the field detection function. By switching the NFC Tag mode, the load is changed, and the electronic device is guided to switch from the LPCD detection mode to the card reader mode to actively read the link content of the Tag.

2. The card transaction method based on field detection according to claim 1, characterized in that In the card searching phase, the terminal polls the NFC Tag mode, the card reader mode, the contact card recognition mode, and the magnetic card recognition mode in sequence, adapts to the current mainstream card payment scenarios, sets the polling time of each mode, and switches to the NFC Tag mode when a contactless card is recognized, so as to realize the selectable transaction scenarios of the electronic wallet and payment application of the mobile electronic device, and returns the card searching result to the transaction layer.

3. The card-based transaction method based on field detection according to claim 1, wherein When a contactless card is recognized, the terminal switches to the NFC Tag mode; In the NFC Tag mode, the terminal distinguishes between a contactless physical card and an electronic wallet based on the field detection function, returns the card searching result for the contactless physical card, and for the electronic wallet, extends the polling time of the NFC Tag mode and waits for communication with the electronic device.

4. The method for card-based transactions based on field detection according to claim 1, wherein When a contactless card is recognized, the terminal switches to the NFC Tag mode; In the NFC Tag mode, the terminal distinguishes between a contactless physical card and an electronic wallet based on the field detection function. For the electronic wallet, it extends the polling time of the NFC Tag mode and waits for communication with the electronic device, and confirms whether the current electronic device is continuously in the LPCD mode. If it is still in the LPCD mode, the NFC Tag mode is closed and then reopened after a delay, causing a load change to guide the electronic device to switch to the card reader mode.

5. The card transaction method based on field detection according to claim 1, wherein Specifically including the card searching phase and the transaction phase; In the card searching phase, the terminal polls the NFC Tag mode, the card reader mode, the contact card recognition mode, and the magnetic card recognition mode of the payment terminal in sequence within the specified time; When the terminal switches to the NFC Tag mode and confirms that the link information in the Tag has been read, to realize the selectable transaction scenarios of the mobile wallet and payment application, it switches to the card reader mode; When the terminal switches to the card reading mode, it sends a card searching instruction. When a contactless card is recognized, if the Tag information has been read, it directly returns the card searching result, otherwise the terminal switches back to the NFC Tag mode again; At this time, it is necessary to distinguish between non-contact physical cards and e-wallets. According to the principle of the non-contact field emitted by the mobile electronic device, detect whether the electronic device is in the LPCD mode or the card reader mode; if the device does not emit a field within the polling time, directly return the card search result of the non-contact physical card, otherwise extend the polling time of the NFC Tag mode, and at the same time the electronic device communicates with the terminal and pops up the Tag; if it is confirmed that the electronic device is continuously in the LPCD detection mode, the terminal will close the current NFC Tag mode, and after a delay, reopen the NFC Tag mode, causing a load change to guide the electronic device to switch to the card reader mode; when the terminal switches to the contact card recognition mode or the magnetic card recognition mode, when a contact card or a magnetic card is detected and inserted into the terminal, exit the current polling mode and return the card search result. In the transaction stage, the terminal switches to the corresponding card interaction mode according to the card search result for transactions.

6. The card-based transaction method based on field detection according to claim 5, wherein According to the principle of the non-contact field emitted by the mobile electronic device, detect whether the electronic device is in the LPCD mode or the card reader mode, which specifically includes the following steps: The LPCD mode of the mobile electronic device adopts a strategy of periodically emitting a non-contact field. When a change in the environment is detected, it actively switches to the card reader mode and issues a card search instruction to confirm again whether the card is in place. To determine whether the current electronic device is in the LPCD mode, after detecting that the electronic device emits a field, extend the time. If the non-contact field of the electronic device is closed at this time, confirm that the device is currently in the LPCD mode, otherwise it is in the card reader mode.

7. The method for card-based transactions based on field detection according to claim 5, wherein It is detected that the current electronic device is in the LPCD mode, and it is impossible to determine whether a change in the environment is detected and switched to the card reader mode before the next non-contact field is emitted. Therefore, before the terminal closes the NFC Tag mode, delay and detect whether the electronic device emits a non-contact field. If a field is detected, it is considered that the electronic device has switched to the card reader mode, and the NFC Tag mode is not selected to be closed. Otherwise, it is considered that the device is still in the LPCD detection mode, and closing the Tag mode causes a load change to guide the electronic device to switch to the card reader mode.

8. The method for card-based transactions based on field detection according to claim 5, characterized in that, In the card search stage, the terminal needs to sequentially poll the NFC Tag mode, the non-contact card recognition mode, the contact card recognition mode, and the magnetic card recognition mode, and return the card search result to the transaction layer; the specific steps are as follows: S1: Initialize the polling time of the NFC Tag mode and other relevant parameters; S2: Initialize the device and turn on the NFC Tag mode; S3: Determine whether the current time exceeds the set polling time. If yes, enter S4; if no, enter S31; S31: Determine whether the transaction object has started, and distinguish between physical non-contact cards and non-physical non-contact cards. If yes, enter S311; if no, return to S3; S311: Determine whether this start is an LPCD detection. If yes, enter S3111; if no, enter S312; S3111: Clear the current time, the device closes the NFC Tag mode, delays and turns on the Tag mode, and enters S312; S312: Determine whether a non-contact card has been detected. If yes, enter 3121; if no, enter S313; S3121: Extend the polling time of the NFC Tag mode and enter S313; S313: Determine whether the current time exceeds the polling time of the NFC Tag mode. If yes, enter S3131; if no, enter S314; S3131: Determine whether a contactless card has been detected. If yes, end directly; if no, enter S4; S314: Determine whether the link information of the NFC Tag has been read. If yes, enter S3131; if no, enter S313; S4: Switch the device mode to the card reader mode, identify the contactless card, and enter S5; S5: Determine whether a contactless card has been identified. If yes, return to S2; if no, enter S6; S6: Switch the device to the contact card identification mode, identify the contact card, and enter S7; S7: Determine whether a contact card has been identified. If yes, end directly; if no, enter S8; S8: Switch the device to the magnetic card identification mode, identify the magnetic card, and enter S9; S9: Determine whether a magnetic card has been identified. If yes, end directly; if no, enter S2.

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