[0001] This invention relates to an interface device for connection between a two-way VHF radio and a handheld data processing device.

BACKGROUND

[0002] Taxi cabs and similar fleet vehicles often include communication devices such as two-way radios in order that a dispatcher can communicate with the driver to allocate customers. Two-way radios of this kind are typically analogue devices operating in the 50 to 500 MHz VHF bands. Systems are available which provide data communication rather than voice communication with the driver in order to provide a listing of available customers for which the driver can bid.

[0003] Taxi drivers can also use mobile telephones or e-mail enabled

telecommunications devices such as smartphones to maintain communication with a dispatcher. However, such devices are relatively expensive to operate as they require a subscription to a mobile phone network for each device. For this reason, taxi companies prefer to operate a two-way radio system, which requires only a radio licence.

[0004] It would be desirable to provide a communications system suitable for taxi cabs and other commercial fleet vehicles that allows the sophisticated data communication capability of a smartphone with the relatively low cost of two-way radio communication.

BRIEF SUMMARY OF THE DISCLOSURE

[0005] In accordance with the present invention there is provided an interface device for connection between a two-way VHF radio and a handheld data processing device (PDA). The interface device comprises a host USB port for connection to a device USB port of the PDA and a microprocessor configured to communicate with the PDA via the host USB port in order to establish a communication channel between the PDA and the interface device. The device is configured to receive data from the PDA via the established communication channel under the control of the PDA and to communicate the data onward via the two- way VHF radio.

[0006] Thus, in accordance with the invention a PDA device can be used to provide relatively sophisticated functionality and communication over a radio interface. Personal digital assistants (PDAs) are handheld computing devices, which are capable of running relatively sophisticated software applications. Such devices often include a universal serial bus (USB) interface for connection to a host computer, for example in order to synchronise data on the PDA and host computer. However, the USB interfaces of PDA devices are typically USB devices (slaves) rather than USB hosts (masters). In the absence of the invention, there is no way to connect a PDA device to a two-way radio. The invention therefore provides a simple solution to providing sophisticated functionality in a taxi cab at relatively low cost.

[0007] The interface device may be configured to receive data from the two-way VHF radio and to communicate the data to the PDA via the established communication channel. Thus, the device typically enables two-way communication via the radio.

[0008] The device may comprise a serial port for connection to a modem input of the two-way VHF radio. Thus, the radio may have an in-built modem, in which case the interface device need only supply digital data to the radio. Typically, however, the device comprises a modem arranged to receive data from the PDA. The modem may comprise an audio port for connection to the two-way VHF radio. The modem may be configured to communicate data received from the PDA to the two-way VHF radio via the audio port. Similarly, the modem may be configured to receive data from the two-way VHF radio via the audio port and to communicate the data to the PDA via the established communication channel. The audio port may be a simple audio output / input. For example, the audio port may comprise a jack socket.

[0009] The communication channel may be a multiplexed communication channel. In particular, the interface device may co-operate with a device driver on the PDA to provide a plurality of multiplexed channels over the communication channel.

[0010] The microprocessor may be configured to respond to control commands received from the PDA via the communication channel. In this way, once the communication channel is established, the PDA may operate as if it is directly connected to the two-way radio via a serial port. Thus, the microprocessor may be configured to respond to control commands for configuration of the communication channel from the PDA.

[0011] The device may comprise at least one further input port for connection to at least one further peripheral device, whereby to enable data communication between the PDA and the peripheral device via the communication channel. The peripheral device may be a taxi toplight, a taxi meter, a printer or a credit card chip and PIN reader, amongst others.

[0012] The invention extends to a USB device driver for a PDA configured to respond to connection to an interface device as described above in order to establish the

communication channel between the PDA and the interface device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 shows schematically an interface device according to an embodiment of the present invention; and

Figure 2 shows schematically the configuration of a system incorporating the interface device of the invention.

[0014] Some applications for the in-car control of a taxi cab run on personal digital assistants (PDAs), permitting the businesses that produce the overall fleet management system to use outsourced standard equipment for the "intelligence" cab-side.

[0015] Using a PDA within a taxi vehicle exposes a number of short-comings of the PDA device, however, most of which arise from the fact that it is a "generic" user device being used within an environment not generally considered for PDAs. Specifically, PDAs have limited connectivity, and certainly are not directed at the specific communication requirements of the internals of a taxi vehicle. Additionally, the power supply available within a vehicle is not normally as stable or predictable as normally specified for a PDA. Finally, PDAs are normally designed to be devices that operate in a secondary role to another more sophisticated system, usually a PC, whereas the role within a taxi vehicle is that of the primary controller within the car.

[0016] An embodiment of the present invention provides a USB adaptor for usage within cars (specifically taxis) that permits a controlling device (a PDA) to connect to a number of peripherals (printers, card-swipe systems).

[0017] As shown in Figure 1 , the interface device ("Starman") of the present invention is located within a taxi vehicle and provides a communications path for the PDA to control a number of peripherals whilst providing power from the car to the PDA. The possible peripherals include: a printer via a standard serial point, a taximeter via a standard serial port, a radio via an embedded modem device, a taxi availability top light, a tamper loop and/or a panic/emergency button. The interface device provides two serial port interfaces, a radio interface, an interface for the monitoring of the taxi top light, an interface for detecting tampering of the setup, an interface for detecting the pressing of an emergency button, a power connector, a USB interface and a visible indicator of status.

[0018] The interface to the radio is via an HD15 male connector, where:

Pin 01 : VRADIO

Pin 02: R_PTTOUT - Sets the radio into transmit

Pin 03: R_TXAUDIO

Pin 04: Power GND

Pin 05: R RXAUDIO Pin 06: Unused

Pin 07: Unused

Pin 08: RJvlMUTE - Microphone Mute

Pin 09: R_VBIAS

Pin 10: R_FSEL1 - Frequency Select Line 1

Pin 1 1 : R_SMUTE - Speaker Mute

Pin 12: Reserved

Pin 13: Reserved

Pin 14: R_PTTIN - Microphone PTT Status

Pin 15: R_FSEL2 - Frequency Select Line 2

[0019] The characteristics of the lines on the HD15 connector match those of existing interfaces in order that the interface device can encode and exchange data between the PDA and a taxi base station over the radio.

[0020] Although PDAs increasingly support acting as controllers of a USB interface (USB hosts), it remains common that some can only operate as slave devices (USB devices). In order to support all possibilities, the interface device of the invention is capable of acting as a USB host when required. The USB interface is capable of providing power to the PDA when operating in "host" mode.

[0021] Each interface device uniquely identifies itself to the PDA application, so that the PDA application can record details of each interface device it encounters in order to minimise the details and information it has to request from the driver each time the PDA is connected to a new interface device (in a different taxi).

[0022] The interface device allows an application on a PDA to configure, and connect to any attached serial devices and the radio port, and to then exchange data with these ports as if the ports were physically present on the PDA itself. The interface provided on the PDA is based on the standard windows interface for using such ports so that the drivers can be used in a standard way. For example, the PDA application can configure the two standard serial ports, independently, changing the transmission speed, byte encoding options and flow control method.

[0023] Figure 2 shows schematically the configuration of the system incorporating the interface device of the invention. The manufacturing application is a simple software application for loading the firmware of the device, performing calibration (if required), running a series of tests and allocating serial numbers. The application communicates with the interface device using a set of administrative commands.

[0024] The PDA drivers associated with interface device come in two parts. The low-lying base driver is an industry standard USB class, which is supported by default by virtually any device that provides USB. This class is for a single virtual serial port, which is referred to here as the CDC COM Port. On top of this, a proprietary driver is installed on the PDA that handles the multiplexing and other parts of the interface device-specific protocol. This driver provides interface device-specific virtual serial ports (referred to here as the SVC COM Ports), which the driver multiplexes across the CDC COM Port.

[0025] The driver seizes control of the CDC COM Port for its own exclusive use if and when an application requests to use one or more SVC COM Ports. The driver also releases the CDC COM Port when it has no further use for it. This is essential to permit the CDC COM Port to be used by other applications in different circumstances (Active Sync, for example) since the PDA may be connected to other systems that are not related to the present interface device.

[0026] The application firmware sits in the centre of numerous interfaces and runs on a microprocessor in the interface device. The firmware is configured to handle: test, calibration and general set up via the admin interface; peripheral control and data exchange between the local devices and the port interface indirectly over the USB interface; low level USB management as a host; power control and LED management; logging of unusual events for support purposes.

[0027] The interface device comprises a microprocessor and some quantity of volatile and non-volatile memory, serial ports, top light interface, emergency button interface, power interface and management circuitry, USB interface and LED indicator.

[0028] The establishment of the USB interface is one sided, controlled and managed by the interface device, which acts as the host side of the USB pairing. Once the

communication channel is established, the exchange of information between the PDA and the interface device is balanced, with either side capable and permitted to send messages at any time. These messages are multiplexed so that an identifier of the serial port (or other interface) that they relate to is embedded within the message itself. This is referred to as the channel number. The channel number has at least five channels plus some spare channel numbers for administrative and test purposes. Since these messages may be responses to earlier commands, a sequencing identifier is embedded in the messages themselves. This is referred to as the sequence number. Each side of the communication stack can determine if they have communicated with the peer before and, when suitable, recover previous session-specific details. This is particularly useful for when trying to seamlessly recover from loss of power, suspension and other USB events.

[0029] The multiplexing protocol permits identification of up to 16 channels and the interconnection of up to 16 devices, providing a rudimentary level of networking should it be required. Each channel, when sending a new message, can determine whether the message must be acknowledged or not. In conjunction with this, message sequencing is also available if needed. Other than that, the protocol establishes the basic framework for message structure, but leaves the detail of the content and meaning of each message open for definition on a channel and device basis.

[0030] There is no explicit functionality for establishing and activating the serial ports that the interface device provides; they are considered as present and useable as soon as the PDA and interface device have an enumerated USB connection.

[0031] There is no explicit functionality for disconnecting or de-activating the serial ports that the interface device provides; they are considered as logically always present and available as soon as the PDA and interface device have an enumerated USB connection.

[0032] Data packets may be received from the application on the PDA for transmission to the associated peripheral attached to the interface device. The driver in the PDA packages and transmits this information to the interface device immediately using a data

transmission message that has the channel identifier for the serial port in question embedded in it. The firmware application on the interface device unpacks and queues this data for output on the appropriate peripheral, and transmits the data character by character as and when it can.

[0033] The PDA may wish to change the serial port characteristics, read line states or perform other control operations on the port. A set of control messages allows for this with port identification, sequencing and acknowledgement being performed in a similar way to data transmission above. The specific control functions include: setting line speed, bits per character and other usual port characteristics; send on/off; read and/or set control line states; flush port.

[0034] Characters received on the serial ports that have peripherals attached are buffered for a brief period of time, e.g. no longer than 10ms. The firmware application performs a "round-robin" collection of the characters buffered and transmits this in packets across the USB interface in order to utilise the interface capacity more efficiently.

Otherwise data transmission from the interface device to the PDA is identical to that from the PDA to the interface device. [0035] Suspension and disconnection of the PDA, and loss of power to the interface device are all in handled in a similar manner, and treated as complete disconnection of the USB connection requiring re-enumeration and establishment of the USB connection at the next connection. However, the interface protocol allows this to appear seamless to the higher level applications since the device identification can be used to store and recover previous sessions.

In summary, an interface device for connection between a two-way VHF radio and a handheld data processing device (PDA) comprises a host USB port for connection to a device USB port of the PDA and a microprocessor configured to communicate with the PDA via the host USB port in order to establish a communication channel between the PDA and the interface device. The device is configured to receive data from the PDA via the established communication channel under the control of the PDA and to communicate the data onward via the two-way VHF radio.

[0036] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0037] Features, integers, characteristics or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0038] Although the invention has been described in the context of a taxi radio data system, the invention may be applied in other contexts. In addition, although the invention has been described in the context of a serial data connection to a VHF radio, the described configuration may be used for connection to other peripherals.