Data Port Solutions for Smart Phones

Smart phones are becoming a popular computing and communication platform. As each new generation of smartphones becomes better at executing processes and data intensive applications that once required computers or dedicated devices. Modern GHz and multi-core processors are now using a fraction of the power required a few years ago to complete real-time tasks.

Smartphones are replacing discrete handheld instruments, just as PCs and laptops are replacing larger, bulkier and more expensive devices: becoming user interfaces and process engines. When this happens, better and faster data ports need to be established between clip in, plug-in or wireless sensors / sensors.

This paper introduces the common smart phone data ports, and introduces the methods that engineers use these solutions to connect various sensors and peripherals, and use smart phones as high-resolution displays, touch screens, process engines and links to the cloud as needed.

in limine

This solution is attractive because it is a low-cost, well-designed and easy to understand technology supported by several high-quality manufacturers. A good example is the maxim 73m2901ce-igv / F IC modem, which has a baud rate of 300 baud to 9600 baud. Since the audio stream is independent, you can separate the input and output data rates. In high noise environments, a more reliable bell 103a can be used for input and 9600 baud V.32 data stream can be used in the outlet. In both cases, these are relatively slow data transmission rates, so these types of applications are usually used for non data intensive and tokenized control and state.

Multichannel barrel jacks, such as 2.5 mm tensility 50-00401, provide mono input channels and stereo output channels in a simple plug-in cable (Figure 1). As a low-cost bolted sensor interface, a simple circuit can use ask, FSK or PSK modulation to provide raw or processed data for smart phones. Even the frequency counter mode can provide gating and updated readings.

Figure 1: the lowest cost connection can use a multi-channel barrel Jack to input and output audio streams into and out of the smartphone. Here, two output streams and one input stream share a common grounding housing.

Note that not all phones and / or tablets have direct mono or stereo microphones or line in. Some headphones that support a microphone may implement a 3-channel plug that contains audio. The old adhesive acoustic coupling rubber shell and bracket are not an elegant solution here, but can be used as part of the equipment when OEM mobile phones or tablets.

It should be noted that the data rate limit of the modem is mainly limited by the characteristics of the telephone line carrying the signal. Since the telephone line is no longer the limiting factor, there is no reason why it is not possible to use the audio output port or dedicated hardware connected to the smartphone to achieve a higher speed modem. This is especially true for smartphones with superior audio channels with higher data rates.

IrDA transceiver

The wireless line of sight port that can use the frame serial asynchronous UART packet structure is IrDA. These transceivers are relatively small, low-cost modules that can be placed near smartphones and transmit data rates from 115.2 kbit / sec to 4 Mbit / sec in packages as small as 2.5 mm.

Although RF technology is invading IR technology for remote control, IR is still the main leader of entertainment system remote control. This mass use keeps these components low-cost and competitive, and makes them a solution for coupling the data connections of smartphones and tablets.

For example, considering Vishay tfdu4301-tt1 115.2 KB / sec low profile transceiver, IR transmitter and PIN photodiode are combined (Fig. 2). The remote control range is up to 12M, the full duplex data link can work at 2.4V, and the separate power supply is used, which allows the transmitter and receiver to use different power levels, can be switched independently, and can be less than 1 in standby mode μ A。

Figure 2: flush or right angle surface mount infrared transceiver modules provide low-cost advantages in large quantities

Small and high-speed links can use Rohm rpm973-h11e2a and other components to support a higher rate of 4 Mbit / sec data rate. This function can also be reduced to 2.4 V and consume more power in idle mode (1 mA), but includes complete remote control built into the function. This simplifies the alarms and alarm types of the sensor module because the established code set is out of the box.

These low-cost transceiver modules are bundled with a very large number of technologies. Modulators and demodulators help distinguish between noise and signals. Note, however, that not all phones or tablets have IrDA like the microphone input jack, so if your goal is a specific smartphone or tablet you may want to OEM or support, this is an I / O technology.


USB port standard has become a general interconnection medium for wired peripherals. The USB length is limited to a few meters, which is very suitable for compact high-speed links. However, unlike its generic name, there are several different standard and proprietary USB connectors.

The most widely deployed USB is USB 2. X, with a peak of about 480 Mbits / sec. For example, traditional support means that USB 2.0 will still support USB 1.1 12 Mbit / sec rate, so locking to the required rate can ensure the accessibility of future generations of standards.

Several excellent independent USB peripheral interface devices can be used to create compact embedded accessories for modern mobile phones. Take microchip's simple 14 pin mcp221-i / SL as an example. It obtains power directly from USB interface and and provides UART and I 2C ports at local end. These are common to most microcontrollers, making it easy to connect directly. Note the GPIO matrix, including a / D and D / A converters (Figure 3). This makes the component a good solution because it contains communication and data acquisition in a common connection medium.

Figure 3: single chip USB interface also includes general UART and I 2C interface for external communication. GPIO pin can be digital input or output, or analog.

An interesting advantage of USB is that it provides a bridgeable monolithic way to connect to various fixed functions, such as Ethernet, ATA, SMBus and SPI, to name a few. Debate continues on whether the next generation of smartphones need to implement USB 3. X or whether it represents too much cost and complexity. The 5 Gbit / sec data rate is an order of magnitude faster than the 480 Mbit / sec data rate of 2.0, but the 3.1 10 Gbit / sec flavor is coming.

No wires required


Wireless interconnection technology provides the best solution for distributed sensor array applications. Many excellent high-speed wireless protocols can be used to route data from various common address locations to central processing units and communication hubs.

Although smartphones and connected tablets may have built-in 3G and 4G connections, this is not a way to connect localized sensors. These cellular networks operate worldwide, and national and international laws and standards may prohibit private deployment of competitive radio wave links. However, for some applications, this particular consistency and licensing may not be a problem; If the use of global cellular network is part of your design, cellular connection devices such as life microsystem lms7002m can provide CDMA, GSM, HSPA, LTE, TD-SCDMA and WCDMA protocol coverage for global connection.

The practical approach of most designs is to take advantage of widely deployed and low-cost wireless protocols, which are directly supported by most smartphones and tablets. One advantage of using a single Wi Fi transceiver chip is that it can create a fairly large distributed sensor network. Low cost wireless routers and switches can be deployed, and sensor information can be transmitted over a long distance.

Simple support components supported by Ti, such as TI's simplelink series product cc3100r11mrgc, encapsulate the 2.4 GHz 16 Mbit / sec Wi Fi 802.11 B / g / N functional network and internal ARM processor. For the Internet of things (IOT), the embedded stack can handle eight TCP or UDP sockets and two TLS and SSL sockets simultaneously, providing sufficient high-speed connections for almost any sensor. However, real HD and high frame rate video may be a problem, especially if it has an extended palette and infrared sensitivity.

Other common protocols implemented by most smartphones and tablets use Bluetooth with sensor arrays, especially Bluetooth low power consumption. Similarly, due to traditional support and dual-mode devices, low-speed mode and higher-speed mode can be used. For components up to 1 Mbit, components such as STMicroelectronics bluenrgqtr (a member of the company's bluenrg Series) utilize the Bluetooth low-power mode version 4. X. The embedded ARM processor has a complete embedded protocol stack, which can provide complete link control and host security (Figure 4). More importantly, this part can act as a master or slave when plotting a 10 Ma peak.

Figure 4: the dedicated communication peripheral chip realizes RF transceiver, power management, security, I / O and timing, making these components an ideal solution for low-power and distributed smart phone sensor array.

Modular EPCOS (TDK) modules are worth considering when a speed of 54 Mbit / sec is required to connect to more demanding sensors at a higher speed. The operating voltage of b30931d7020y918 is 1.8 V, providing UART output for embedded interface. Up to 65 Ma for reception and up to 345 Ma for transmission. If a speed of 54 Mbit / sec makes the unit go to sleep faster, the overall power may be reduced.

In general, engineers should note that the number of open sockets or the number of tethered devices may be restrictions on Wi Fi and Bluetooth respectively, so verify your topology constraints before submitting.

Other interfaces that can be used are video streams that can be used to transmit high-speed data (if you don't care about affecting the display). The display memory can be used to store data blocks of HDMI ports, such as repeated bursts. Although it may be a novel idea for high-speed burst of output data, it is not practical for most people.

As we have shown in this article, for most applications, plug-ins and wireless ports are modern smartphones and tablets flexible enough to handle any sensor problems that may arise in the near future. So please select your technology and continue.

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