 Now we are going to look at the fast transfer mode. The SC25-DV fast transfer mode is where a RAM-like buffer acts like a mailbox. To send data from the I2C host to the RF reader, the I2C host first writes the message containing data into the mailbox. The RF user must pull on the mailbox control register to check for the present of a message from I2C in the mailbox. Once read, the mailbox is clear and the I2C host can write the next data message. The I2C host is informed that message has been read by RF user through a GPO interruption or by pulling on the mailbox control registers. Power to the SC25-DV VCC pin is required for this task, but this is given as the microcontroller needs power to operate anyway. In summary, in I2C, access to the fast transfer mode buffer is done in bytes by address. There will be no rollover. It must start at the first byte of the mailbox at 2008 hax. For the RF interface, access in bytes with specific commands such as write message and read message. All commands that are needed to access the fast transfer mode are also available in fast data rate, which is around 53 kbps. There are also no priority between I2C and RF, and as you know is more or less a first come first serve, that means if the mailbox is free or available, then either the I2C or RF can access. Of course, as we discussed earlier, fast transfer mode requires power to operate. Looking at this scope shot, you can kind of see the advantage between writing to and from versus EE prom. The write is most prominently visible because of the erasure time needed for EE prom. The read is the same for EE prom and the fast transfer mode buffer. Here we illustrate the time it takes to transfer 100 kilobytes of data from smartphones to the host microcontroller. It's not clear why the galaxy express takes twice as long as the average, and the HTC One X takes 10 times as long due to the fact that it probably allows only the slowest ISO 15693 data rate. As a comparison, it takes around 10 minutes to move the same data via the EE prom. Now we're going to do some example involving fast transfer mode. Here you can choose either the SC25R3911B discovery as the NFC reader, or you can use an NFC enabled smartphone. We will follow through with the SC25R3911B discovery board as the reader. We will first transfer data from the reader to the SEM32 host. Then we will transfer data from the SEM32 host to the reader. First put the two boards in proximity to each other. You just need them to be close enough for magnetic induction to take place. Since the antenna of the SC25DV board is very large, you don't necessarily put them on top of each other. Starting at the main menu of the SC25DV discovery board, tap the FTM button. A new menu screen will appear, and this is when the SEM32 microcontroller is ready to receive data from the reader. From the reader, click on the SC25 tag editor button and choose ISO 15693. Click on dynamic tags and choose SC25DV04K. You will see a new menu with inventory as the beginning tab and FTM demos as the ending tab. Click on FTM demos tab and choose R2H image transfer radio button. After clicking the R2H image transfer radio button, choose an image in the data folder which is located in SC25 tag editor directory. Once the button start R2H data transfer is clicked, the transfer will start and progress will be shown via a status bar. After completion, CRC and duration will be displayed. Now, let's start sending image from the SC25DV discovery board to the reader. Get to the previous image transfer screen, then tap on the bottom left icon. Choose an image to transfer, select by pressing either left or right button on the screen. Make sure that the reader GUI is set for H2R image transfer radio button. Ok, now we are going to look at energy harvesting capability of the SC25DV. As the circuit diagram suggests, AC potential appearing at the antenna input are rectified. Filter and go straight out to the VEH pin via a FET switch. The VEH output is not regulated but it is limited under 4V and we recommend that some sort of external filter is used. Also, EH output can be delivered during the following mode, RF disabled, RF sleep state and low power down mode. There are some important points that need to be taken into account when working with SC25DV energy harvesting. During load modulation for communication, energy harvesting output is temporarily reduced. If the output is overdrawn, the reader may not be able to communicate with the SC25DV. So there are three possible scenarios of energy harvesting operation. EH not delivered simply because the magnetic field generating by the reader is not strong enough or the tag antenna is too small. The second scenario is that EH is delivered but RF communication is not possible. This is the result of overdrawn condition at the pin. And the third scenario is that EH is delivered and communication is possible. How much power can be delivered? You might ask. At 2.2V and using an ISO Class 1 antenna about the size of a credit card, the SC25DV delivers a maximum of 8mA at the field strength of 5-6A. In these two charts, it shows what happens to energy harvesting output when modulation is at 100% and when modulation is at 10%. Now we're going to do some example involving energy harvesting. We're going to measure the energy harvested by the SC25DV. And this is a schematic of the energy harvesting circuit on the evaluation board. It has some ADC input so that the microcontroller can actually measure and put out how much voltage and currents are being delivered by the SC25DV. From the SC25R3911B GUI software, select reader app and click on configuration. The RF field will be on as indicated by the blue transmitter LED. On the SC25DV discovery board, tap on the SC25DV button and then tap on EH button. Put the SC25DV antenna over the reader board. Be sure not to short out any components. You will notice the harvested voltage and current. Notice the amber LED or LD2 which changes from low to high in intensity as the SC25DV discovery board gets closer to the reader board. Move the board around in different positions and see the result power being harvested. Now let's look at the RF management of the SC25DV. The RF interface can be set in three states. RF normal, disable and sleep mode. In RF normal mode, RF requests are processed and responded normally. However, if I2C is busy, RF requests will not be processed. Inventory and stay quiet commands are not answered. Addressed commands are not answered while all the commands are answered with error code OFFX. In RF disabled mode, the behavior is similar to condition when I2C is busy. In RF sleep mode, RF is off and all RF requests are ignored. Now we are going to discuss the power management of the SC25DV. It is important to understand how this thing is working as we actually have two possible supply source RF field and VCC. Access to EEPROM memory can be done without any VCC or in passive mode. Vice versa, access to EEPROM memory can be done with VCC and no RF field. Access to mailbox can only be done if VCC is present. We are going to look at the capability container and NDEV. SC25DV is delivered in non-preformatted state. This means that the end user has to write the capability container before reading and writing standard NDEV messages. You can find out more about these features by reading application note 4911. Let's go to an exercise with NDEV message. We are going to first write the message via I2C using the SCM32 microcontroller. Then we will read the message using the SC25R3911B RF reader. From the main menu window of the SC25DV, tap on the NDEV icon. From there, you have several types of NDEV message to choose from. Once chosen, you can tap on that particular type and a default message will be stored in the SC25DV. You can read the NDEV message out either with an NFC-enabled phone or the SC25R3911B Discovery board. Click on the SD25 tag editor. From the drop-down menu under ISO 15693 tab, click on NFC type 5 NDEV message user interface. From there, you can click on read NDEV message to see what is stored on the tag.