 Let�s now focus our attention on the ST25R3911B device. First we�ll look at the main features, then we�ll look at some design tips for designing your own board, and then we�ll look at the support ecosystem for the device. The 3911B has an SPI that can handle up to 6 megabits per second and also has a 96-byte 5V. It can handle data rates up to 6.8 megabits per second and can supply up to 1.4 watts of output power at 5 volts. The output of the device is differential, however it can be configured to run two single-ended antennas. The temperature range of the device is minus 40 degrees C to plus 125 degrees C and the input supply range is 2.4 volts to 5.5 volts. The 3911B comes in a QFN32 package. The 3912 also comes in a wafer level chip scale package. In addition to the supporting standard protocols, the 3911B also has a transparent and stream mode to implement things such as my fair classic or custom protocols. And finally, in terms of special features, the 3911 has automatic antenna tuning, capacitive and inductive wake-up modes, and dynamic power output. Now let�s take a look at the internal block diagram of the 3911B. We see that it is supplied from two voltages, VDDIO and VDD. VDDIO supplies the level shifters needed for the SPI interface. VDD supplies internal regulators. These regulators provide voltages for the analog, the digital and the RF portions of the device. For low power wake-up, we have the phase and amplitude detector and the ADD converter in addition to the capacitive sensor and the wake-up timer. We also have an external field detector which is used when in active peer-to-peer mode. There�s also a logic section which contains the FIFO, the control logic, the SPI interface and the framing for the various protocols that the device can handle. On each of the trim pins, there�s an internal switch that can be used to switch in the external automatic antenna tuning capacitors. The crystal oscillator is supplied by an external crystal of either 13.56 MHz or 27 MHz. The 3911B has high output power and sensitivity. The high output power is due to the low impedance drivers that are capable of generating more than one watt of output power. The benefit of this is EMVCO certification is possible without using an external booster. Higher output power also means that for standard tags the read range is increased and for dynamic tags, the tag has more energy to harvest so that it can power more devices. And finally, this increased output power makes the 3911B a very viable candidate for working in metal encapsulation such as door locks. The 3911B receiver has 10 times higher sensitivity than any other competitor. This is due to the three independent gain stages on both the phase and amplitude channels of the receiver. The device also features dynamic power output gain and squelch. Dynamic power output allows the reader to adjust the power dynamically via the dynamic power output control. This is based on a hysteresis and an upper and lower threshold determined by the user. This is a very useful feature when going through EMV certification where the minimum and maximum field strength is listed at each of the measurement points. The active gain control or AGC allows the reader to adapt its receiver settings based upon the power level of the card. And finally, squelch allows you to scale the signal level based upon the noise on the receiver. It's time to move on to some of the hands-on examples featuring the polling capabilities of the discovery board. The goal is simply to show the tag detection capabilities of the reader. So for this, we'll set it up so that the reader periodically detects tags in the field. Both the polling period and the protocols can be set via the GUI and the detection of the tag will be signaled by both LEDs on the reader board as well as in the GUI. This will allow you to experiment with the protocols that are supported by the reader. In addition, you can experiment by reading different tags at different distances, tags at different angles, and also multiple tags in the field. To set the discovery board up for polling, you must first start the GUI and plug in the discovery board to your computer. Then go through the startup sequence as described earlier in this presentation. From there, you simply select the polling tab and then select which protocol of card that you want to read. You can select one, some, or all depending on the cards you have. And then finally, simply hit fine to begin the polling sequence. There's also optional settings so that you can set time to live and the delay between the polling cycles. To test the polling mode, simply put a tag in the field. In the GUI, you'll see the unique ID, the type of tag, the number of times the tag has been read, and the last time the tag was read. In addition, on the discovery boards, you'll see the LEDs light up of the type of tag that you're reading. From here, you can measure the maximum distance between tag and reader, different angles between the tag and reader, and you can also try multiple tag detection. To stop the polling, simply hit stop on the polling tab. Another feature of the 3911B is automatic antenna tuning. Automatic antenna tuning increases the range of an HF reader and sustains maximum power to the field with the best efficiency. So AAT can be used to compensate for environmental conditions that cause phase or amplitude shifts when operating. AAT can also reduce production costs by compensating for variances of components that are in the matching circuit. It can also adjust to different housings that the antenna is put in. In addition, it can be used for multiple tag placement because as each tag is placed in the field, it detunes the reader antenna more and more. So AAT, in this case, can be used to retune the antenna as more tags come in the field. Automatic antenna tuning is achieved by using external capacitors that can be switched in, in parallel, to the parallel capacitor of the matching circuit. There are four capacitors for each differential pair, and these capacitors are binary weighted, giving you 16 trim values for each RFO. There are three tuning algorithms available. One is hardware-based that's internal to the chip. There's also two software-based, one optimized for phase and another optimized for amplitude. An AAT can be used during any time of the polling sequence simply by using the D8 command to calibrate the antenna. To see how automatic antenna tuning changes the impedance of the antenna as seen by the reader, you simply connect up your VNA to the output pins of the 3911B. But please note that prior to hooking up your VNA, set register 27 of the 3911B to FF. If this step is not done, you will damage your VNA. After connecting up our VNA, we can actually measure the change as a result of the automatic antenna tuning. Here we see at trim 0, our 13.56 MHz is matched at 36.6 ohms. When we change the trim to 15, we can see that our impedance changes to 8.6 ohms, and also our power consumption has increased as well. Our next example shows the features of the automatic antenna tuning. The goal of this example is to show the parameters, both amplitude and phase, as they are seen by the reader. It's also to demonstrate how these parameters change with a different environment, and finally to demonstrate the possibilities of the automatic antenna tuning feature. First, we must begin with the ideal state of the input of the receiver. First, we have to make sure that we're at the recommended receiver amplitude. For the 3911B, this is typically between 2.4 and 2.7 volts. We have to make sure that the input to the receiver stays below 3.1 volts per the datasheet. The recommended phase is 90 degrees. This puts you at the middle of the range or the middle of the measurable range of the internal ADC. First, we'll look at the effects of devices that are brought in the field by measuring the received amplitude and phase of the discovery board. To do this, we must set up the measurement in the 3911B GUI simply by going to the antenna features tab and hitting continuous measurement. Once continuous measurement is selected, you'll see the measurement of the amplitude and phase in the bottom portion of the GUI screen. In addition, you'll see a graphical interpretation of both those measurements as well. In order to see the effect that devices in the field have, simply place a device in the field. In this case, I suggest some metal because this has the greatest influence on the antenna. And you'll see both the measurements change as well as the graphical interpretation of those of that data. Then you can simply change the trimming values of your AAT to try to normalize that measurement. To demonstrate the automatic antenna tuning, we once again go to antenna features and select an algorithm either the hardware based or one of the two software based. If you choose the software based, please put in a target phase or target amplitude. From there, we simply hit continuous auto adjust antenna. To observe the automatic antenna tuning, simply place a piece of metal in the field. You will see the trim value change as the metal affects the antenna. You'll also see the automatic antenna tuning trying to compensate for the metal in the field and see the phase and amplitude measurements change. An additional benefit of the 3911B is its support for very high bit rate. So this is ideal for e-government and passports since these documents contain large amounts of data. The 3911B can handle data transfer of up to 6.8 megabits per second. So what this equates to is an increase in speed of about 8 times over a standard reader. The output of the 3911B is differential. And in differential mode, the highest amount of output power is available to the antenna. However, the device can also be configured for either one or two single-ended antennas. Configuring the device for single-ended reduces the output power available to the antenna by half. When configured for one single-ended antenna, the number of matching components is also reduced by half. The benefit of configuring for two single-ended antennas is that these antennas can be placed in different places and different orientations. And no RF switch is needed as this is done via internal register settings. This is very valuable in systems where the orientation of the card to the reader is unknown. Communication with the reader is done via an SPI interface that handles up to 6 megabits per second. It also has a 96 byte buffer and has an IRQ output. The SPI operation modes are register, read, write, FIFO load and reset and direct command mode. The direct commands for the 3911B can be found in the datasheet. There are also two special modes, stream and transport mode, that can be utilized if you need to implement custom protocols, or protocols that aren't directly supported by the 3911B. So these would be protocols that had different framing, different subcarriers, or different coding. In stream mode, all the transfers are done through the FIFO, and the timing is done by the 3911B. The bit coding, decoding, parity and CRC are done in software. And this mode is typically used to implement variants of 14443. Transparent mode on the other hand, the 3911B acts as an RF run-in and the control logic becomes transparent. So in this mode, the external microcontroller does everything. It controls the TX modulator and gets the received output. So all the bit coding, decoding, parity and CRC, like the stream mode, is also done in software. However, in transparent mode, this can be used for any custom protocol. The 3911B has three wake-up modes, and all the circuitry for the wake-up modes is internal to the device. So all the parameters that you need to program in order to set up the wake-ups are internal to the device, so no MCU is required to run the wake-up. And then capacitive and inductive wake-up can also be combined, so you don't have to use one or the other. You can use all three if needed. Capacitive wake-up detects a capacitive change between two pads that are laid out close to the antenna. So something like a hand approach in the antenna would cause an interrupt, which would wake the microcontroller up. Inductive wake-up, on the other hand, is usually triggered by a card in the field, since a card will usually cause a change in either phase or amplitude of the antenna. The difference between the two wake-ups is capacitive wake-up uses much less current. However, it may wake up more often because anything can wake it up. Capacitive sensing only requires two additional capacitive plates connected to CSO and the CSI pins of the device. Generally, this is typically just traces laid out on the board. For inductive sensing, the antenna is used to detect changes in the field. The power savings of the wake-up modes is due to the short pulse that's used to sense if there's a change in environment as compared to the normal polling cycle. As we see here, in a normal polling cycle, the duration is anywhere from 5 to 100 milliseconds and draws about 200 milliamps. However, for inductive amplitude and phase, that duration is cut down to 25 to 35 microseconds. So while it still consumes the peak current, it's done for a very short amount of time, which ends up in savings of power. Capacitive sense, while the pulse is much longer, the power savings comes from the fact that the field does not have to be turned on in order to look for a change. There are general wake-up functions that are associated with both capacitive and inductive wake-up. The first is the timer period. And the timer period is simply how often the system wakes up to see if there's a change. This can be set anywhere from 10 to 800 milliseconds in 16 steps. The delta window size allows you to set up the sensitivity of the wake-up. This can be set from 1 to 15 steps of difference of a 256 step 8-bit ADC. Essentially, this defines how far a measured value has to be from the reference value in order to produce a wake-up. Auto-arranging can be used to compensate for slow environmental changes. For instance, if an antenna was placed behind glass and there's rain on the glass, this would cause a change in capacitance. So auto averaging can be set to average over the last 4, 8, or 16 or 32-bit values. Capacitive wake-up power consumption is based upon two factors. First is the sleep wake-up mode. So this can be programmed anywhere from 10 to 800 milliseconds. And during this time, you're going to be drawing about 3.6 microamps of current. And then there's the actual measurement, which takes about 200 microseconds. So during this stage, you're drawing about 1.1 milliamps of current. So the measurement is set. However, the amount or how often you wake up is programmable. Inductive wake-up can either be amplitude or phase. Amplitude wake-up is based upon an amplitude change due to the detuning of the antenna. For phase, it's based on a phase change due to the detuning of the antenna. So in both cases here, the HF field is actually turned on and then measured and then compared with values from before. Inductive wake-up power consumption is determined by 3 values. Like capacitive, it's the sleep wake-up mode, which is programmed between 10 and 800 milliseconds. So in this mode, capacitive, it's only drawing about 3.6 microamps. And also like the capacitive wake-up is the actual measurement, which is 20 microseconds. In this case, the current used for the wake-up is actually higher because the field has to be turned on in order to do the measurement. And finally, the crystal startup, which is 1 millisecond. And this is also a consuming power of about 5.4 milliamps. Now let's use the hardware to learn how to set up and use the low power wake-up modes. The goal is to show the setting of the reference value for both the modes and then evaluate the capacitive and inductive wake-up modes for performance. So the thing to remember here is both capacitive and inductive wake-up have some very similar settings here. And that is the set of the reference value, the set of the timer period, and the set of the window size. The reference value characterizes the default state of either the phase or amplitude of the antenna or of the capacitive sensor. To obtain this value, we simply hit measure, and this will measure the reference value. It's very important to do this measurement when nothing is close to the antenna or close to the capacitive sensors. Once we have the reference measurement, we write that measurement to the offset register by pressing measurement to offset. You'll see that value appear here in the offset register. Next we set up the delta window size. So this is the variance from the offset measurement that will trigger a wake-up. In addition, we can set the timer period, and this is how often the system wakes up to check the value. Here we see the value inside the offset register. When a measurement is outside the delta window size, you'll see an interrupt generated here. To set up capacitive wake-up mode, go to the wake-up tab of the 3911 discovery GUI. From here, you would select capacitive wake-up, which is on box number two. And please note here where it says, run notebook on battery to avoid noise from mains. So USB voltage generates lots of noise, and this could cause problems with the measurement. So it's best to run it off the battery of the laptop. From here, we would calibrate the sensor of the capacitive input, so we can either do that by manually selecting it here, or we can do an auto-calibrate. In most cases, auto-calibration is what you want to do. From here, like it was explained before, you would hit measure, and then measure to offset, and you would see the offset appear here. You would then set up your wake-up for your delta window size and your timer period, and then simply hit start. To generate interrupts, you would simply bring your hand closer or further away from the capacitive pads. Some of the things you can try are to put your hand closer to the reader, or try the same thing with a tag or dynamic tag, or try other things you have around. You can also play with the sensor gain and the delta window size to see how it affects the sensitivity of the receiver. For inductive wake-up, you simply select the inductive wake-up mode, so either inductive phase or inductive amplitude. And as before, you set that up by taking the reference measurement, writing that measurement to the offset register, selecting the delta window size, and the timer period, and simply hitting start. So what you can observe with the inductive wake-up is the same as capacitive. So put your hand closer to the reader and see if you can trigger an interrupt, and then try the same thing with a tag or dynamic tag, and then other things around you. As before, you can play with the delta window size and the timer function to see how things vary from there, and then compare the results with the capacitive wake-up mode. Thank you for viewing this presentation.