Feature: Evalboards
Figure 4: The PTX100R evalboard
Te design of the purely capacitive matching network required for
the PTX100R controller is so simple that it can be configured almost entirely with Panthronics’s tools. Panthronics provides a model that the developer can run in a free simulator: by entering the inductance and resistance values of the antenna, it generates values for the matching network. Customer experiences show that these automatically-generated
values are very close to the optimal values found aſter hardware testing. Te PTX100R evalboard kit also facilitates this second-stage testing. Te kit is supplied with a controller board and an attached board containing a 50mm x 50mm antenna for initial evaluation. When developing a new design, this antenna board may be snapped off, and the controller board connected to the prototype’s antenna. Te design soſtware supplied with the PTX100R evalboard has a
GUI for configuring controller settings. It also enables the user to run the full suite of EMVCo 3.0 tests at the press of a button in tandem with any EMVCo-compatible test instrument; see Figure 2. Te configuration options controlled via the GUI include settings
for wave shaping and for power output. In both cases, the PTX100R eases compliance with the EMVCo 3.0 standard. Control of wave shaping is far more precise than with conventional square-wave controllers because of the absence of an EMC filter with its distorting effect; when emitted by the transmitter, the shape of the wave is maintained at the antenna.
Power handling Power output is also set up via the GUI. Tis is an important feature of EMVCo 3.0 compliance: to meet the standard’s requirement for operating volume – the volume of 3D space in which a viable signal can be received by the card device – the controller must be capable of transmitting at high power when the receiver is a long distance away from the terminal. But this same high power output may saturate the receiver when touching the terminal’s screen. Te PTX100R manages this problem by providing a Dynamic
Power Control feature. Te device will automatically switch between a high-power and a low-power modes, with hysteresis, based on an RSSI (received signal strength indicator) signal that it generates. Te settings for the power modes can be adjusted simply via the development soſtware’s GUI: the high and low power levels are both arbitrary and may be set by the developer in the GUI, and then tested by connecting the PTX100R controller board to the terminal’s antenna.
22 June 2021
www.electronicsworld.co.uk
Te tool also provides a useful Q (quality)-factor test – the
development soſtware performs a sweep through the 12-15MHz frequency band, then plots the device’s frequency response across the band and provides a calculated Q-factor and centre frequency; see Figure 3. Tis supports EMVCo compliance efforts, because the Q value of a terminal must stay within a certain band – at a too-high or too-low level of Q, NFC signalling is impaired, which can fail the terminal’s compliance test. Te centre frequency produced by the PTX100R evalboard’s test quickly shows whether the matching network is operating at or close to the NFC 13.56MHz frequency.
Protocol software Te most difficult and time-consuming parts of conventional PoS terminal development involve the RF circuit. But the EMVCo specifications also cover digital operations. Te PTX100R evalboard helps accelerate development here too, because of the controller’s ‘split-stack’ approach to EMVCo soſtware: low-level protocol layer operations are implemented in the controller itself, whilst the application layer soſtware runs in the host microcontroller or processor. Tis may appear unusual, since other NFC transceivers are either front ends, which implement only the physical layer and offload all soſtware operations to the host, or NFC controllers, which include an embedded microcontroller and implement the entire system including the protocol and application layers. Most PoS terminals today use an NFC front-end, because it
gives the manufacturer freedom to implement the application in a way that best suits the application. Te PTX100R implementation maintains this freedom, whilst liſting the burden of implementing low-level protocol layer functions from the terminal manufacturer.
Design for compliance Te PTX100R evalboard includes a Pmod header for connection to microcontroller boards. Initial project configuration is particularly quick for users of Renesas Synergy microcontrollers, because Panthronics supplies a fully-tested version of its soſtware that is already ported to the TB-S3A1 – a development board for the Synergy S3A1 series of microcontrollers. For many reasons, then, Panthronics feels confident in its claim
that PoS terminal development will be at least as fast with the PTX100R evalboard (Figure 4) as it is in any other development environment.
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