CC2431 System-on-Chip for 2.4 GHz ZigBee™/ IEEE 802.15.4 with Location Engine Applications • • • • • • ZigBee™ systems 2.4 GHz IEEE 802.15.4 systems Home/building automation Industrial Control and Monitoring Low power wireless sensor networks Access Control • • • • • • PC peripherals Set-top boxes and remote controls Consumer Electronics Container/Vehicle Tracking Active RFID Inventory Control Product Description The CC2431 is a true System-On-Chip (SOC) for wireless sensor networking ZigBee™ / 802.15.4 solutions with location detection engine hardware onboard allowing location accuracy of around 3 meters or less. It enables ZigBee™ nodes to be built with very low total bill-of-material costs. The CC2431 combines the excellent performance of the leading CC2420 RF transceiver with an industry-standard enhanced 8051 MCU, 128 KB flash memory, 8 KB RAM and many other powerful features. Combined with the industry leading ZigBee™ protocol stack (Z-Stack™) from Figure 8 Wireless / Chipcon, the CC2431 provides the market’s most competitive ZigBee™ solution. The CC2431 is highly suited for systems where ultra low power consumption is required. This is achieved by various operating modes. Short transition times between these modes further ensure low power consumption. Key Features • • • • • • • • • Location Engine accurately calculates the location of a node in a network High performance and low power 8051 microcontroller core. 2.4 GHz IEEE 802.15.4 compliant RF transceiver (industry leading CC2420 radio core). Excellent receiver sensitivity and robustness to interferers 128 KB in-system programmable flash 8 KB RAM, 4 KB with data retention in all power modes Powerful DMA functionality Very few external components Only a single crystal needed for mesh network systems • • • • • • • • Low current consumption (RX: 27mA, TX: 25mA, microcontroller running at 32 MHz) Only 0.9µA current consumption in powerdown mode, where external interrupts or the RTC can wake up the system Less than 0.6µA current consumption in stand-by mode, where external interrupts can wake up the system Very fast transition times from low-power modes to active mode enables ultra low average power consumption in low dutycycle systems CSMA/CA hardware support Wide supply voltage range (2.0V – 3.6V) Digital RSSI / LQI support Battery monitor and temperature sensor SWRS034 Page 1 of 14 CC2431 Key Features (continued) • • • • • 8-14 bits ADC with up to eight inputs 128-bit AES security coprocessor Two powerful USARTs with support for several serial protocols. Hardware debug support Watchdog timer • • • • One IEEE 802.15.4 MAC Timer, one general 16-bit timer and two 8-bit timers RoHS compliant 7x7mm QLP48 package 21 general I/O pins, two with 20mA sink/source capability Powerful and flexible development tools available Note: The CC2431 and the CC2430 are pin compatible, and the MCU and RF parts of the CC2430-F128 are identical to the CC2431 except the Location Engine. This data sheet complements the CC2430 data sheet with a description of the Location Engine. For complete information about the CC2431, please refer to the CC2430 data sheet in addition to this data sheet. SWRS034 Page 2 of 14 CC2431 Table Of Contents 1 REGISTER CONVENTIONS ................................................................................................................. 4 2 2.1 2.2 3 LOCATION ENGINE .............................................................................................................................. 5 LOCATION ENGINE OPERATION ................................................................................................................... 5 LOCATION ENGINE REGISTERS .................................................................................................................. 10 ORDERING INFORMATION .............................................................................................................. 12 4 4.1 4.2 4.3 4.4 4.5 5 GENERAL INFORMATION ................................................................................................................ 12 DOCUMENT HISTORY ................................................................................................................................. 12 PRODUCT STATUS DEFINITIONS ................................................................................................................. 12 DISCLAIMER .............................................................................................................................................. 13 TRADEMARKS ............................................................................................................................................ 13 LIFE SUPPORT POLICY ............................................................................................................................... 13 ADDRESS INFORMATION ................................................................................................................. 14 SWRS034 Page 3 of 14 CC2431 1 Register conventions Each RF register is described in a separate table. The table heading is given in the following format: REGISTER NAME (XDATA Address) In the register descriptions, each register bit is shown with a symbol indicating the access mode of the register bit. The register values are always given in binary notation unless prefixed by ‘0x’ which indicates hexadecimal notation. Symbol Access Mode R/W Read/write R Read only R0 Read as 0 R1 Read as 1 W Write only W0 Write as 0 W1 Write as 1 H0 Hardware clear H1 Hardware set Table 1: Register bit conventions SWRS034 Page 4 of 14 CC2431 2 Location Engine The Location Engine is used to estimate the position of nodes in an ad-hoc wireless network. Reference nodes exist with known coordinates, typically because they are part of an installed infrastructure. Other nodes are blind nodes, whose coordinates need to be estimated. These blind nodes are often mobile and attached to assets that need to be tracked. The Location Engine implements a distributed computation algorithm that uses received signal strength indicator (RSSI) values from known reference nodes, such as mobile neighbor nodes with the same Location Engine, or fixed infrastructure nodes. Performing location calculations at the node level reduces network traffic and communication delays otherwise present in a centralized computation approach. The Location Engine has the following main features: • Three to eight reference nodes can be used for the location estimation algorithm • Location estimate with resolution of 0.5 meters • Time to estimate node location less than 40 µs • Location range 64 x 64 meters • Location error can be less than 3 meters, depending on factors described below • Runs location estimation with minimum CPU usage To achieve the best possible accuracy one should use antennas that have nearisotropic radiation characteristics. The location error depends on signal environment, deployment pattern of reference nodes and the density of reference nodes in a given area. In general, having more reference nodes available improves the accuracy of the location estimation. 2.1 Location Engine Operation This section describes the basic steps required to obtain location estimates from the Location Engine. The Location Engine requires a set of three to eight reference coordinates to be input together with a set of measured parameters. The output from the Location Engine consists of a pair of estimated location coordinates. Before any input data is written, the Location Engine must be enabled by writing a 1 to the enable bit, LOCENG.EN. When the Location Engine is not in use, writing a 0 to LOCENG.EN will reduce the power consumption of the CC2431 by gating off the Engine’s clock signal. Figure 1 shows the basic operation of the Location Engine. SWRS034 Page 5 of 14 CC2431 LOCENG.EN=1 Load coordinate pairs? yes LOCENG.REFLD=1 no Load reference coordinate pairs no Loaded 8 coordinate pairs? yes LOCENG.REFLD=0 LOCENG.PARLD=1 Load measured parameter or zero for unused reference no Loaded 10 parameters? yes LOCENG.PARLD=0 LOCENG.RUN=1 Wait no LOCENG.DONE=1 ? yes Read LOCX, LOCY and LOCMIN LOCENG.EN=0 Figure 1: Location Engine Operation SWRS034 Page 6 of 14 CC2431 2.1.1 Reference Coordinates The Location Engine requires a set of between three and eight reference coordinates [x0, y0, x1, y1, … x7, y7] to be input. The reference coordinates express each reference nodes position in meters, as unsigned values in the interval [0, 63.75] meters. The finest possible resolution is 0.25 meter. The format used is fixed-point data with the two LSBs representing the fractional part and the remaining six bits representing the integer part. Reference coordinates are loaded into the RF register REFCOORD. Before writing to REFCOORD, a 1 must be written to the register bit LOCENG.REFLD to indicate that a set of reference coordinates are being written. Once the coordinate load process commences (LOCENG.REFLD =1), eight coordinate pairs must always be written. However, it is possible for the Location Engine to use less than eight reference coordinates, by marking certain reference coordinates as unused. Zeros can be used to fill the unused reference coordinate slots, and they will be interpreted as unused when 0.0 is loaded as the RSSI value for those reference coordinates. The reference coordinates are written in the order [x0, y0, x1, y1, …, x7, y7] to the register REFCOORD. After all coordinates have been written, a 0 is written to the register bit LOCENG.REFLD. 2.1.2 Measured Parameters After the reference coordinates have been written, a set of measured parameters must be input to the Location Engine. These parameters consist of two radio parameters and eight RSSI values. The radio parameters are the values A and n. These radio parameters are used in the Engine’s algorithm used to find the estimated location. The parameters A and n can be adjusted to describe the propagation environment in which a network of devices will operate. 2.1.2.1 Parameter Definitions The measured parameters are described in this section together with how these should be estimated. 2.1.2.1.1 Parameter A The radio parameter A is defined as the absolute value of the average power in dBm received at a close-in reference distance of one meter from the transmitter, assuming an omni-directional radiation pattern. For example, if the mean received power at one meter is -40 dBm, the parameter A is specified as 40. The Engine expects the parameter A to be in the range [30.0, 50.0] with precision 0.5. The parameter A is given as an unsigned fixed-point value where the LSB bit is the fractional bit and the remaining bits are the integer part. A typical value for A is 40.0. 2.1.2.1.2 Parameter n The radio parameter n is defined as the path loss exponent that describes the rate at which the signal power decays with increasing distance from the transmitter. This decay is proportional to d-n where d is the distance between transmitter and receiver. The actual parameter n value written to the Location Engine is an integer index value selected from a lookup table shown in Table 2. As an example, in the case when the value n=2.98 is found from measurements, the closest available value of n in the lookup table is 3.00, corresponding to index 13. Therefore, the integer value 13 is used for the parameter n written to the Location Engine. Refer to section 2.1.2.1.3 in order to find the value for n to be used. SWRS034 Page 7 of 14 CC2431 n index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 n 1.000 1.250 1.500 1.750 1.875 2.000 2.125 2.250 2.375 2.500 2.625 2.750 2.875 3.000 3.125 3.250 n index 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 n 3.375 3.500 3.625 3.750 3.875 4.000 4.125 4.250 4.375 4.500 4.625 5.000 5.500 6.000 7.000 8.000 Table 2: n parameter lookup table The parameter n is written to the Location Engine as an integer index in the range [0, 31] as the index is given as an integer value with no fractional bits, e.g. the value n = 7 is loaded as 00000111. A typical value for n is 13. 2.1.2.1.3 Parameter Estimation The parameters A and n can be estimated empirically by collecting RSSI data (and therefore path loss data) for which the distances between the transmitting and receiving devices are known. Figure 2 is a scatter plot of abs(RSSI) data versus log distance in meters. A least-squares best-fit line is used to glean the specific values of A and n for the environment in which the data were measured: • A is the y-intercept of the line, and • n is the slope of the line The data in Figure 2 give A=42.4 and n=2.98 for that environment. Note that the plot in this example does not show the actual y-intercept i.e. the point on the line where x=0. The value of A loaded into the engine in this case would by 42.5. The value of n loaded into the engine, is seen to be 13 from Table 2. SWRS034 Page 8 of 14 CC2431 Path Loss vs. log-distance for source 0x85, Z=2.1082. A=42.4103, n=2.9773 95 90 85 Path Loss (dB) 80 75 70 65 60 55 50 45 2 4 6 8 10*log10(distance) 10 12 14 Figure 2: Path loss vs. log distance 2.1.2.1.4 RSSI Values The RSSI values are the RSSI measurements corresponding to the set of reference coordinates. The RSSI values are within the interval [-40 dBm, -95 dBm] with precision 0.5 dBm. The negative sign is removed in the value written. As an example, in the case where the value RSSI = -50.35 dB, this would be written into the location engine as 50.5. Note that a value of 0.0 must be written as RSSI value for unused reference coordinates. The engine will not function correctly if only some of the parameters are loaded. 2.1.2.2 Loading Parameters All measured parameters are loaded into the RF register MEASPARM. Before writing to MEASPARM, a 1 must be written to the register bit LOCENG.PARLD to indicate that a set of measured parameters are being written. Once the parameter load process commences (LOCENG.PARLD =1), all ten parameters must be written. The measured parameters must be written in the order [A, n, rssi0, rssi1, … rssi7] to Once the the MEASPARM register. parameter load process commences (LOCENG.PARLD =1) it must be completed. Eight RSSI values must be written, so any unused slots must be written as zeros. After all ten parameters have been written, a 0 must be written to the register bit LOCENG.PARLD. 2.1.3 Location Estimation The estimated location coordinates are given in meters in the interval [0.0, 63.5] with precision 0.5 m. The data format uses the LSB bit as the fractional part. When reference coordinates and measured parameters have been loaded, the location estimate is calculated by writing 1 to the LOCENG.RUN register bit. The estimated coordinates can be read from the LOCX and LOCY registers when LOCENG.DONE is set to 1. This occurs 1200 system clock cycles (16/32 MHz) after LOCENG.RUN was set to 1. The Location Engine does not produce any interrupt requests. The estimated coordinates remain valid in the LOCX and LOCY registers until new SWRS034 Page 9 of 14 CC2431 results have been calculated or until a reset. • Note that LOCENG.EN must be 1 during operation of the Location Engine. • 2.2 Location Engine Registers This section describes the RF registers associated with the Location Engine. These registers are: • LOCENG Location Engine control and status • REFCOORD Reference coordinates input • MEASPARM Measured parameters input LOCX Location estimate LOCY Location estimate LOCMIN Minimum function X coordinate Y coordinate • estimate The RF registers reside in XDATA memory space. Table 3 gives an overview of register addresses while the remaining tables in this section describe each register in detail. Refer also to section 1 for Register conventions. For the remaining RF registers refer to the CC2430 Data Sheet. Table 3 : Overview of Location Engine RF registers XDATA Address Register name Description 0xDF55 REFCOORD Reference coordinates input 0xDF56 MEASPARM Measured parameters input 0xDF57 LOCENG Location Engine control and status 0xDF58 LOCX Location estimate X coordinate 0xDF59 LOCY Location estimate Y coordinate 0xDF5A LOCMIN Minimum function estimate 0xDF60 CHVER Chip Version 0xDF61 CHIPID Chip Identification Bit Name Reset R/W Description 7:0 REFCOORD 0 R/W Location Engine reference coordinate [x0, y0, x1, y1, … x7, y7] Table 4: Register REFCOORD (0xDF55) Bit Name Reset R/W Description 7:0 MEASPARM 0 R/W Location Engine measured parameters of channel and reference nodes [A, n, rssi0, rssi1, …, rssi7] Table 5: Register MEASPARM (0xDF56) SWRS034 Page 10 of 14 CC2431 Bit Name Reset R/W Description 7:5 - 00 R0 Reserved, read as 0. 4 EN 0 R/W Enable location engine 0 Disable location engine 1 Enable location engine 3 DONE 0 R Estimation completed. After 1 has been written to RUN, this bit is cleared and then set to 1 when the estimated data is ready. 2 PARLD 0 R/W Load parameters. This bit shall be written as 1 before the set of parameters are written to MEASPARM. Write 0 to this bit after the last parameter has been written. 1 REFLD 0 R/W Load reference coordinates. This bit shall be written as 1 before the set of coordinates are written to REFCOORD. Write 0 to this bit after the last coordinate has been written. 0 RUN 0 R0W1 Location estimate start. This bit shall be written as 1 when desired coordinates and parameters have been written to REFCOORD and MEASPARM registers. Estimation process starts when 1 is written to this bit. Always read as 0. Table 6: Register LOCENG (0xDF57) Bit Name Reset R/W Description 7:0 LOCX 00h R Location estimate X coordinate. Table 7: Register LOCX (0xDF58) Bit Name Reset R/W Description 7:0 LOCY 00h R Location estimate Y coordinate. Table 8: Register LOCY (0xDF59) Bit Name Reset R/W Description 7:0 LOCMIN 00h R Location estimate minimum value Table 9: Register LOCMIN (0xDF5A) Bit Name Reset R/W Description 7:0 VERSION[7:0] 0x01 R Chip revision number Table 10: Register CHVER (0xDF60) Bit Name Reset R/W Description 7:0 CHIPID[7:0] 0x89 R Chip identification number. Always read as 0x89. Table 11: Register CHIPID (0xDF61) SWRS034 Page 11 of 14 CC2431 3 Ordering Information Ordering part number Description Minimum Order Quantity (MOQ) 1371 CC2431-RTB1 CC2431, QLP48 package, RoHS compliant Pb-free assembly in tubes with 43 pcs per tube, Single Chip RF Transceiver 43 1372 CC2431-RTR1 CC2431, QLP48 package, RoHS compliant Pb-free assembly, tape and reel with 2500 pcs per reel, Single Chip RF Transceiver 2500 1367 CC2431DK CC2431 ZigBee Development Kit 1 1368 CC2431ZDK Pro CC2431 ZigBee Development Kit including support and training 1 Table 12: Ordering Information 4 General Information 4.1 Document History Revision Date Description/Changes 1.0 2005-11-30 First release Table 13: Document History 4.2 Product Status Definitions Data Sheet Identification Product Status Definition Advance Information Planned or Under Development This data sheet contains the design specifications for product development. Specifications may change in any manner without notice. Preliminary Engineering Samples and First Production This data sheet contains preliminary data, and supplementary data will be published at a later date. Chipcon reserves the right to make changes at any time without notice in order to improve design and supply the best possible product. No Identification Noted Full Production This data sheet contains the final specifications. Chipcon reserves the right to make changes at any time without notice in order to improve design and supply the best possible product. Obsolete Not In Production This data sheet contains specifications on a product that has been discontinued by Chipcon. The data sheet is printed for reference information only. Table 14: Product Status Definitions SWRS034 Page 12 of 14 CC2431 4.3 Disclaimer Chipcon AS believes the information contained herein is correct and accurate at the time of this printing. However, Chipcon AS reserves the right to make changes to this product without notice. Chipcon AS does not assume any responsibility for the use of the described product; neither does it convey any license under its patent rights, or the rights of others. The latest updates are available at the Chipcon website or by contacting Chipcon directly. As far as possible, major changes of product specifications and functionality, will be stated in product specific Errata Notes published at the Chipcon website. Customers are encouraged to sign up for the Chipcon Newsletter for the most recent updates on products and support tools. When a product is discontinued this will be done according to Chipcon’s procedure for obsolete products as described in Chipcon’s Quality Manual. This includes informing about last-time-buy options. The Quality Manual can be downloaded from Chipcon’s website. Compliance with regulations is dependent on complete system performance. It is the customer’s responsibility to ensure that the system complies with regulations. The ZigBee Specification includes intellectual property rights of ZigBee Alliance member/promoter companies. Chipcon is a ZigBee Alliance Promoter. Under the ZigBee Alliance terms of use, no part of the Specification may be used by a company in the development of a product for sale without such company becoming a member of the ZigBee Alliance. Therefore, the Figure 8 Wireless Z-Stack™ may only be used for commercial purposes by ZigBee Alliance member companies. If a customer desires to use the Figure 8 Wireless Z-Stack™ or any other third party ZigBee stack together with a product described in this datasheet, the customer is responsible for complying with the applicable ZigBee Alliance policies. See http://www.zigbee.org. This Chipcon product contains Flash memory code protection. However, Chipcon does not guarantee the security of this protection. Chipcon customers using or selling these products with program code do so at their own risk and agree to fully indemnify Chipcon AS for any damages resulting from the use or sale of such products. Chipcon believes that the Flash memory protection used in this product is one of the most secure in the market today when used in the intended manner and under normal conditions. However, there might be methods to breach the code protection feature. Neither Chipcon nor any other semiconductor manufacturer can guarantee the security of their code protection. Code protection does not mean that we are guaranteeing the product as “unbreakable”. This Chipcon product contains hardware AES encryption. Chipcon does not guarantee the security of the key protection or the security of the encryption scheme. Chipcon customers using or selling products with AES do so at their own risk and agree to fully indemnify Chipcon AS for any damages resulting from the use or sale of such products. It is the Chipcon customer's responsibility to ensure that sale or export/import of products including this Chipcon product with AES encryption is sold with the required export/import licenses, if necessary, and does not violate any applicable export/import and/or other trade restrictions. 4.4 Trademarks SmartRF® is a registered trademark of Chipcon AS. SmartRF® is Chipcon's RF technology platform with RF library cells, modules and design expertise. Based on SmartRF® technology Chipcon develops standard component RF circuits as well as full custom ASICs based on customer requirements and this technology. All other trademarks, registered trademarks and product names are the sole property of their respective owners. 4.5 Life Support Policy This Chipcon product is not designed for use in life support appliances, devices, or other systems where malfunction can reasonably be expected to result in significant personal injury to the user, or as a critical component in any life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. Chipcon AS customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Chipcon AS for any damages resulting from any improper use or sale. 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