Just what we need, another short-range wireless technology, right? That was my first reaction to Cypress Semiconductor’s CyFi solution. But this device, which especially suits low-cost sensor and machine monitor and control applications, lets designers develop wireless products quickly and easily with minimal hardware or software experience.
The RF portion of the CyFi offers a 2.4-GHz ISM transceiver that can transmit in any one of 80 1-MHz wide bands over the 2.4-to 2.483-GHz range. Its frequency agility lets it move to avoid interference. By using DSSS with GFSK modulation, it can provide excellent link reliability. A 32-bit chip code is used at a rate of 250 kchips/s. The max data rate is 1 Mbit/s, but it will adjust downward to 250 or 125 kbits/s as needed.
The transmit power is variable from –5 dBm to +4 dBm in seven steps, allowing the device to adapt to link conditions while saving power. On short, high-reliability, low-speed links, the radio reverts to straight GFSK. If the going gets tough, the DSSS kicks in and provides an extra 9 to 13 dBm of coding gain. The –97-dBm receiver sensitivity includes RSSI.
CyFi offers some really interesting benefits. First is reliability. Operating in the already crowded 2.4-GHz band with Wi-Fi, Bluetooth, ZigBee, cordless phones, microwave ovens, and who knows what else is challenging. The DSSS helps, but the radio also automatically looks for interfering Wi-Fi or other nearby signals and switches channels to one that is clear. Power output automatically adjusts for a solid link.
Also, CyFi is very power-efficient. It has low average power consumption, active power management, a sleep mode, and the automatically adjusting transmit power. The transmit current with –5-dBm output is 20.8 mA. With 0 dBm out, the TX current is 26.2 mA. At maximum power of +4 dBm, the current is 34.1 mA. Receive power is 21.2 mA. Sleep current is only 0.8 µA. Based on typical sensor usage, battery life expectancy is up to four years.
Next, the product is really easy to use. The pre-wired modules are pre-certified. A simple protocol stack is provided with a star network configuration. And, the development software features drag-and-drop firmware modules, meaning that design is almost a point-and-click process.
Finally, if you have ever developed a wireless device, you know you always need an embedded controller to handle the protocol and other operations. The popular Cypress PSoC Programmable System on a Chip embedded controller supports the CyFi module. It features a wide range of analog and digital mixed-signal I/O circuitry like ADCs, DACs, amplifiers, comparators, counters, timers, PWM, and the usual mix of I/O interfaces. The IDE lets designers build most projects from scratch using the configurable analog and digital blocks and firmware. Programming can be done in C or assembler if needed.
You don’t have to invent your own protocol as you sometimes have to if you’re building a wireless system from scratch with low-cost ISM-band radios. The packet-based protocol supports a star network. Only one master node or hub is supported, but it can handle up to 250 remote nodes. It is one of the simplest and smallest (memory-wise) wireless networking protocols available. The hub needs only about 8 kbytes of memory, while a node only needs about 5 kbytes. ZigBee, Wi-Fi, and other protocols are much more complex and real memory hogs in comparison.
CyFi competes with some really good and well entrenched alternatives, especially ZigBee, Z-Wave, and Bluetooth. But its interference immunity, frequency agility, low power, and especially simple protocol all add up to a new option that should be able to hold its own.
A key part of the overall package is the PSoC controller, which has been around for a while and has found lots of applications. It’s a flash-based equivalent of a field-programmable ASIC without lead-time or NRE penalties. The PSoC devices integrate configurable analog and digital circuits controlled by an on-chip microcontroller that really cuts the need for external components and lowers costs.
Also, the PSoC controller includes up to 32 kbytes of flash, 2 kbytes of SRAM, an 8x8 multiplier with a 32-bit accumulator, power and sleep monitoring circuits, and a hardware I2C interface. Analog circuits include amplifiers, comparators, ADCs, DACs, filters, timers, counters, PWM, and both UART and SPI interfaces. Programmable gain amplifiers and up to 14-bit ADCs are available.
The CYRF7936 is the CyFi transceiver chip. The PSoC FirstTouch Starter Kit with CyFi Low Power RF is a low-cost USB thumb drive kit that includes the PSoC Integrated Development Environment">IDE software, a sense and control dashboard for data collection, a PC dongle with RF, a multifunction board, an RF expansion board with power amplifiers for longer-range applications, and two battery boards. Designers can also use the kit to leverage the touch sensing, temperature sensing, light sensing, and proximity capabilities of the PSoC devices.
The CY3271-EXP1 is an environmental sensing kit that enables a wireless sensor solution with pressure, humidity, temperature, and ambient light sensors. The Cy3271-RFBOARD RF expansion kit is an add-on to the CY3271 that provides two additional RF expansion slots and an AAA battery board. The CY3210-CYFI general-purpose development kit enables prototyping and debugging of the PSoC devices and CyFi transceivers. It also includes two development boards, two PSoC modules, and three CyFi modules to build prototypes. All of these products are available now.
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