Method for controlling an NFC device

Abstract

Method for controlling an NFC device. This description relates to a method for controlling a first NFC device (102) comprising an NFC controller (110) connected to an antenna (204), wherein a charging mode of a second, remote NFC device (108) via the antenna (204) is interrupted following detection, by the NFC controller (110), of a change in the impedance of the antenna (204), the interruption being followed by the initiation of communication, via the antenna (204), with a third, remote NFC device (112). Figure for the abstract: Fig. 4

Description

Title of the invention: Method for controlling an NFC device Technical field

[0001] The present description relates generally to methods for controlling NFC (Near Field Communication) devices and associated NFC devices. Prior art

[0002] NFC communication devices are becoming increasingly widespread and are used in many electronic devices, particularly mobile phones (smartphones).

[0003] NFC protocols, as defined by the NFC Forum, enable communication or charging of NFC devices. However, current devices do not allow these two functions to be implemented efficiently and with minimal manufacturing cost. Summary of the invention

[0004] There is a need for improvement of NFC devices as well as their control methods.

[0005] One embodiment overcomes all or part of the drawbacks of known NFC methods and devices.

[0006] One embodiment provides a method for controlling a first NFC device comprising an NFC controller connected to an antenna, in which a charging mode of a second remote NFC device by the antenna is interrupted following detection, by the NFC controller, of a change in impedance of the antenna, the interruption being followed by the initiation of communication, via the antenna, with a third remote NFC device.

[0007] One embodiment provides an NFC device comprising an NFC controller connected to an antenna;

[0008] the NFC controller being configured to interrupt a charging mode of a second remote NFC device by the antenna following detection, by the NFC controller, of a change in impedance of the antenna;

[0009] the interruption being followed by the initiation of a communication, via the antenna, with a third remote NFC device.

[0010] In one embodiment, the antenna comprises at least two windings in series.

[0011] In one embodiment, said windings comprise one or more turns.

[0012] In one embodiment, the number of turns of one of the windings is comprised between 6 and 8 inclusive.

[0013] In one embodiment, one of said windings defines a first surface area and a second winding defines a second surface area, the first surface area being at least twice as large as the second surface area.

[0014] In one embodiment, one of said windings is arranged within another of said windings.

[0015] In one embodiment, one of said windings is arranged outside another of said windings.

[0016] In one embodiment, the antenna comprises two windings; one of said windings being adapted for NFC charging of the second NFC device and the other for NFC detection and communication with the third NFC device.

[0017] In one embodiment, the antenna comprises another winding, in series with said two windings, and adapted for NFC charging of a fourth NFC device.

[0018] In one embodiment, following detection, the NFC controller implements an interrogation mode.

[0019] In one embodiment, the charging mode is resumed at the end of communication.

[0020] One embodiment provides a mobile telephone comprising a device such as described above and configured to implement the method as described above.

[0021] One embodiment provides a system comprising: - a telephone as described above; - a second NFC device; and - a third NFC device.

[0022] In one embodiment, the second device is a stylus.

[0023] In one embodiment, the system comprises a fourth NFC device, the second and fourth NFC devices being NFC devices configured to emit sounds. Brief description of the drawings

[0024] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0025] [Fig.l] represents a schematic view of an example of an NFC communication system;

[0026] [Fig.2] represents a schematic view of an NFC communication system according to one embodiment;

[0027] [Fig.3] represents an embodiment of an antenna of the system of [Fig.2];

[0028] [Fig.4] represents a method of controlling the NFC device of [Fig.2] according to an embodiment;

[0029] [Fig.5] represents an example of implementation of the control method of [Fig.4]; and

[0030] [Fig.6] represents another example of implementation of the control method of [Fig.4], Description of the embodiments

[0031] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0032] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed.

[0033] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0034] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0035] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0036] NFC or near-field communication systems use a radiofrequency electromagnetic field generated by a device (terminal or reader) to communicate with another device (card). The same device can, particularly in the case of mobile phones, operate in reader mode by generating a field intended for another device, or in card mode by capturing a field generated by another device. This technology concerns the establishment of very short-distance communications (less than ten centimeters) between two devices.

[0037] This NFC technology also allows an NFC device to charge one or more other NFC devices placed nearby.

[0038] In the present description, the case of a system in which the NFC devices are compatible with NFC technology according to the NFC Forum is considered.

[0039] [Fig.l] represents a schematic view of an NFC communication system 100.

[0040] The NFC system 100 comprises an electronic device 130, for example a telephone or smartphone, implementing a first NFC device 102, which comprises a first and a second antenna 104, 106. The system for example also comprises a second NFC device 108, for example a stylus which is configured for example to be inserted into the smartphone 130. The system 100 for example also comprises a third NFC device 112 external to the first device 102 or to the electronic device 130.

[0041] The first device 102 comprises for example two NFC controllers 110, 114 connected, preferably connected, respectively to the antenna 106 and 104 by one or more impedance matching circuits -not illustrated-.

[0042] The antenna 104 comprises for example one or more turns whose shape is adapted to concentrate the electromagnetic field towards the second device 108.

[0043] The antenna 106 comprises, for example, one or more turns whose shape is adapted to detect and communicate with the third device 112 when the latter enters the near field of interaction provided by the NFC protocol.

[0044] An electromagnetic field at 13.56 MHz is used between the first and third NFC devices to obtain NFC communication with, for example, a legacy mode, either in reader or card mode.

[0045] The charging of the second NFC device 108 is carried out, with the same frequency, via the antenna 104, with the second NFC device 108 in a listening mode (listener mode in English) and the NFC controller 114 in a polling mode (poller mode or polling mode in English). The polling mode consists of an emission of periodic bursts of electromagnetic field.

[0046] The example of [Fig.l], the fact that there is one NFC controller per antenna, makes it possible to charge the second NFC device and at the same time detect and then communicate with the third NFC device 112. However, this example is expensive to manufacture.

[0047] It is possible to consider using only one NFC controller instead of controllers 110 and 114 and to use only one antenna. However, in this case, detection of other NFC objects cannot be implemented during the charging mode. In this case, it could be considered to alternate charging and remote device search phases. However, this reduces the charging efficiency.

[0048] The described embodiments provide a method for controlling the first NFC device (102) comprising an NFC controller connected to an antenna, in which a charging mode of the second remote NFC device by the antenna is interrupted following detection, by the NFC controller, of a change in impedance of the antenna, the interruption being followed by the initiation of a communication, via the antenna, with the third remote device.

[0049] This allows the third remote device to be detected while charging the second device. The efficiency of charging and detection are not degraded compared to the example of [Fig.l] while saving component costs.

[0050] [Fig.2] represents a schematic view of an NFC communication system 200 according to one embodiment.

[0051] The NFC system 200 is similar to the system 100 of [Fig.l] except that the first NFC device 102 comprises a single NFC antenna 204 in place of the first and second antennas 104, 106. The first device 102 of [Fig.2] further comprises only a single NFC controller 110 connected, preferably connected, to the antenna 204 by an impedance matching circuit -not shown-.

[0052] The antenna 204 is configured to cover a portion of the NFC device 108 sensitive to the NFC field and also extends more widely within the apparatus 130 to be able to serve for the detection of the remote NFC device 112.

[0053] In the illustrated example, a fourth NFC device 206, optional, is part of the system 200. This NFC device 206 is arranged for example within the apparatus 206 and has a part sensitive to the NFC field which is superimposed on a part of the antenna 204 to be able to be charged. In this case, the NFC devices 108 and 206 are for example NFC devices configured to emit sounds such as earphones otherwise called earpieces or even a stylus and an earphone.

[0054] The example of [Fig.2] makes it possible to detect the third remote device 112 while loading the second device 108 as well as the fourth device 206 and this with the same performance as the case of [Fig.l] but at a lower production cost.

[0055] [Fig. 3] represents an embodiment of an antenna of the system of [Fig. 2]. More particularly [Fig. 3] represents the antenna 204 in the case where only the NFC device 108 is present, the antenna 204 of [Fig. 3] not applying as such to the case where the optional device 206 is present.

[0056] In the illustrated example, the antenna 204 comprises at least two windings in series 304 and 306. The winding 304 is connected by one terminal to a connection pad and the winding 306 is connected by another terminal to another connection pad. The winding 304 comprises 6 turns and the winding 306 comprises 2 turns. The winding 304 is placed to be superimposed on the device 108. The shape of the winding 304 is more grouped than the shape of the winding 306. This makes it possible to optimize and locally increase the electromagnetic field at the device 108 when the latter is of thin shape, for example in the case of a stylus. The more extended shape of the winding 306 makes it possible to be more sensitive to an electromagnetic field of a remote NFC device to facilitate its detection, for example.

[0057] The number of turns is for example between 1 inclusive and 10. In one example, The number of turns of the windings can be chosen between 6 and 8 inclusive to locally focus the intensity of the electromagnetic field. It is nevertheless wise to keep the number of turns less than 10 to avoid resonance effects which should be avoided.

[0058] In the illustrated example, the winding 306 defines a first surface and the winding 304 defines a second surface. The term surface is understood to mean the area defined inside the outermost turn of the windings. In one example, the first surface is at least twice as large as the second surface. The area of ​​the first surface is, for example, greater than 200 mmA2 and the area of ​​the second surface less than 100 mmA2. Having a winding with a smaller area makes it possible not to disturb the winding with the larger area.

[0059] In the example illustrated, the winding 304 is arranged within the winding 306 and in the same plane. In this case, it is appropriate to check that their connection implies a direction of current passing through them which has the same direction so that the electromagnetic fields do not cancel each other out.

[0060] In another example not illustrated, the winding 304 is arranged outside the winding 306. In this case, the direction of the current is not necessarily the same between the two windings.

[0061] The winding 304 is adapted for charging the NFC device 108 and the winding 306 for NFC communication with the NFC device 112.

[0062] The winding 304 is arranged to cover the NFC antenna of the device 108 as much as possible, which makes it possible, in addition to increasing the coupling between the two antennas, not to detect the device 108 when communication is implemented with the device 112 via the winding 306.

[0063] The advantage of having a larger winding 306 than winding 304 is that it prevents device 108 from masking detection of device 112 while ensuring efficient charging with the smaller winding 304.

[0064] In the example not illustrated where a fourth NFC device 206 is present in the system 200, then an additional winding is provided in the antenna 204, for example of a shape similar to the winding 304, but arranged to overlap with the part of the device 206 which is sensitive for the NFC charge. This additional winding is for example connected in series or in parallel with the windings 304 and 306. In this case, the additional winding can be arranged inside or outside the winding 306.

[0065] In a manner not illustrated, regions comprising ferrite are for example arranged between the antenna 204 and the rest of the apparatus 130 in order to limit electromagnetic interactions.

[0066] [Fig.4] represents a method of controlling the NFC device of [Fig.2] according to an embodiment.

[0067] In a step 402 (Charging NFC device(s)), the NFC controller 110 is in a charging mode for charging the device 108.

[0068] In a step 404 (Detect antenna impedance change while charging), which is for example implemented at the same time as step 402, the NFC controller 110 is configured to analyze the impedance variations of the antenna 204. In this example, a protocol called foreign object detection (FOD) can be used. If an impedance variation is detected then a step 406 (NFC device detected?) is implemented. In step 406, the NFC controller 110 implements a polling mode if there is an NFC card nearby, and an electrical field detection (EFD) if an NFC device in card or reader mode is recognized, for example the device 112, (Y branch), then a step 408 (Stop charging) is implemented. For example, an anti-collision process is implemented at this time to check that there is only one card nearby.

[0069] If an NFC device in card or reader mode is not recognized (branch N), for example due to the absence of an NFC device nearby, then step 402 is implemented.

[0070] In step 408, the charging mode of the device 108 is interrupted.

[0071] In a step 410 (Initiate communication with tag or reader) which is implemented implemented at the same time or following step 408, a legacy mode is implemented by the NFC controller 110 for communication between the device 112 via the antenna 204 and more particularly via the winding 306. In one example, low power detection is used by the legacy mode (LPTD, Low Power Tag Detection in English).

[0072] [Fig. 5] represents an example of implementation of the control method of [Fig. 4]. More particularly, the example of [Fig. 5] describes a mode of implementation of the detection of the change in impedance.

[0073] The detection of the change in impedance consists, for example, of in-line and quadrature measurements of the signal captured by the antenna. A calibration is also potentially implemented before the measurements to define one or more thresholds. When the threshold is crossed, then a change in impedance is detected. In one example, the threshold is stored in a memory, for example non-volatile, of the device 130.

[0074] In the example shown, the amplitude of the antenna impedance is expressed in volts as a function of time (Time). Before a time tl (No impedance change), the impedance is relatively stable at its nominal value VNom. Between time tl and a later time t2 (Transition), the amplitude decreases, for example, linearly until it reaches a threshold at VMm and then remains stable at this level VMm. From time t2, a impedance change is detected (Impedance change). In one example, the V Min threshold is a percentage of the nominal value obtained by calibration.

[0075] [Fig.6] represents another example of implementation of the control method of [Fig.4]. More particularly, the example of [Fig.6] describes another mode of implementation of the detection of the impedance change.

[0076] The example in [Fig.6] is similar to that in [Fig.5] except that the threshold is a voltage VMax which is higher than the nominal voltage VN0M. In one example, the threshold VMax is a percentage of the nominal value obtained by calibration. Between time t1 and time t2 (Transition), the amplitude increases, for example, linearly until it reaches the threshold at VMax and then remains stable at this level VMax. From time t2, a change in impedance is detected (Impedance change).

[0077] When the communication with the device 112 is finished, the controller 110 implements step 402 again with the load of the device 108 (or even 206 when it is present).

[0078] Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants could be combined, and other variants will occur to those skilled in the art. In particular, the method of [Fig. 4], for example, also applies to the case where a fourth NFC device 206 is used. In this case, the person skilled in the art will also stop charging the device 206 if communication is initiated with the device 112.

[0079] Finally, the practical implementation of the embodiments and variants described is within the reach of the person skilled in the art from the functional indications given above. In particular, as regards the type of communication or load implemented by the controller 110 through the antenna 204, the modulation used is for example of type A, B, felica or even type V. The person skilled in the art will choose for example between these types so as not to interfere with the other infrastructures of the system 200.

Claims

Claims

1. NFC device (102) comprising an NFC controller (110) connected to an antenna (204); the NFC controller (110) being configured to interrupt a charging mode of a second NFC device (108) remote by the antenna (204) following a detection, by the NFC controller (110), of a change in impedance of the antenna (204); the interruption being followed by the initiation of a communication, via the antenna (204), with a third NFC device (112) remote.

2. Device according to claim 1, wherein the antenna (204) comprises at least two windings (304, 306) in series.

3. A device according to claim 2, wherein said windings (304, 306) comprise one or more turns.

4. Device according to claim 3, in which the number of turns of one of the windings is between 6 and 8 inclusive.

5. A device according to any one of claims 2 to 4, wherein one of said windings (306) defines a first surface and a second winding (304) defines a second surface, the first surface being at least twice as large as the second surface.

6. A device according to any one of claims 2 to 5, wherein one of said windings (304) is arranged within another of said windings (306).

7. A device according to any one of claims 2 to 5, wherein one of said windings is arranged outside another of said windings.

8. Device according to any one of claims 2 to 7 wherein the antenna (204) comprises two windings; one of said windings (304) being adapted to NFC charging of the second NFC device (108) and the other (306) to NFC detection and communication with the third NFC device (112).

9. Device according to claim 8, wherein the antenna (204) comprises another winding, in series with said two windings (304, 306), and adapted for NFC charging of a fourth NFC device (206).

10. Device according to any one of claims 1 to 9, wherein following detection, the NFC controller (110) implements a polling mode.

11. Device according to any one of claims 1 to 10, in which the charging mode is resumed at the end of communication.

12. A method of controlling a first NFC device (102) according to any one of claims 1 to 11, wherein the interruption is followed by the initiation of communication, via the antenna (204), with a third remote NFC device (112).

13. A mobile telephone comprising a device according to any one of claims 1 to 11 and configured to implement the method according to claim 12.

14. System comprising: - a telephone according to claim 13; - a second NFC device (108); and - a third NFC device (112).

15. System according to the preceding claim, in which the second device is a stylus.

16. The system of claim 14 or 15, the system comprising a fourth NFC device (206), the second and fourth NFC devices (108, 206) being NFC devices configured to emit sounds.

Images