Atmel Germany S31SM V4 00 Users Manual
AVR2044: RCB128RFA1 -
Hardware User Manual
Features
• Stand alone operable Radio Controller Board (RCB)
• The design is based on the single chip ATmega128RFA1 to support
IEEE 802.15.4™, ZigBee™, 6LoWPAN, RF4CE, SP100, WirelessHART™ and ISM
Applications
• FCC-ID: VNR-S31SM-V4-00
• Japan TELEC: 005WWCA0425
• SMA RF connector
• Simple user interface with button and LED’s
• Board Information EEPROM containing
- MAC Address
- Board identification, features and serial number
- Crystal calibration values
• 2xAAA batteries for stand alone operation
• 60 pin extension connector to interface with application specific hardware
Application Note
1 Introduction
The RCB128RFA1 user manual describes the usage, design, and layout of the
ATmega128RFA1 radio controller board.
Figure 1-1. RCB128RFA1 PCB Photo
Rev. 8339A-AVR-09/10
2 Disclaimer
3 Overview
Typical values contained in this application note are based on simulations and testing
of individual examples.
Any information about third party materials or parts is included into this document for
convenience. The vendor may have changed the information in between. Check the
individual part information for latest changes.
The RCB128RFA1 is designed to provide a reference design for the single chip
microcontroller and radio transceiver ATmega128RFA1 [1]. The IC integrates a
powerful 8-bit AVR RISC microcontroller, an IEEE802.15.4-compliant transceiver and
additional periphery. The built-in radio transceiver supports the worldwide accessible
2.4 GHz ISM band.
The system is designed to demonstrate standard based applications like
ZigBee/IEEE 802.15.4, ZigBee RF4CE, and 6LoWPAN as well as high data rate ISM
applications. The SMA antenna connector allows either operation with the antenna
provided together with the RCB or to perform conducted RF performance
measurements.
The RF section has been shielded to eliminate interference from external sources to
the ATmega128RFA1. To investigate the reference design area, the shield can be
opened by removing the snap-in cover while the RCB is not in operation.
Most peripheral features of the ATmega128RFA1 where made available through two
expansion connectors (EXT0/1). There is a variety of base boards available for the
RCB family.
Figure 3-1. RCB128RFA1 with Removed Snap-In Cover
4 Mechanical Description
RCB’s, demonstrating radio transceiver and microcontroller capabilities, are equipped
with two 50 mil, 30 pin connectors (ETX0/1), separated 22 mm from each other to
interface to various port extension boards (base boards).
The RCB128RFA1 has no on-board antenna, so that a board separation into an
electronic and an antenna section is not required. When used with a quarter wave
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4.1.1 Mechanical Dimensions
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antenna, mounted at the SMA connector, the board will act as a ground plane for this
antenna.
This design with RF shield is implementing one M2.5 mounting hole (see Figure 4-1).
In consequence, one mounting bolt has to be removed on several base boards types
to mount the RCB128RFA1 in a correct position.
The other mounting hole is reserved for a battery holder. If battery operation is
required, base boards should not make use of this mount.
Figure 4-1 shows the EXT0/1 interface connector position referred to pin1, since most
of the CAD tools using this pin as a placement reference. Please pay attention to the
connector key location at pin 30 and the mirrored placement of a male counterpart
connector when designing a new base board. The connector pin 1 is marked using a
rectangular pad. See Figure 4-2 and Figure 8-5 also.
The PCB is standard 1.5 mm FR4 material with 2 copper layers. Due to panelization
and cutting process, the dimension of the outer board edge may vary up to +0,1mm.
Figure 4-1. RCB128RFA1 – Mechanical Drawing (Dimensions in mm)
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4.1.2 Interface Connector Specification
Figure 4-2. RCB128RFA1 – Interface Connector Drawing
The base board interface connector EXT0/1, mounted on the RCB, is a 30 pin, 50 mil
type from SAMTEC.
The detailed part number is: SFM-115-L2-S-D-LC.
L2 is the low insertion force (LIF) variant to allow easy mounting.
The drawing shown in Figure 4-2 is a copy taken from a SAMTEC datasheet. Check
the latest datasheet for possible updates and changes.
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4.1.3 Application (Base) Board Connectors
Figure 4-3. Application Board Connector Drawing
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The drawing in Figure 4-3 shows the connector to be used on a base board to
interface the RCB EXT0/1 connectors.
The detailed SAMTEC part number is: TFM-115-02-S-D.
Alternatively a Tyco part can be used: Tyco 5-104655-4
Note: The Tyco part requires a different footprint design!
The drawing shown in Figure 4-3 is a copy taken from a SAMTEC datasheet. Check
the latest datasheet for possible updates and changes.
5 Functional Description
Figure 5-1 illustrates the RCB setup in general. It mainly consists of an
ATmega128RFA1 and some periphery. An ID-EEPROM stores MAC address and
additional board information. This information is stored in a separate EEPROM to
avoid accidental data erase during microcontroller firmware development.
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5
Figure 5-1. Radio Controller Board - Block Diagram
32
16
ATmega128RFA1
Expansion
Connector
ID
Expansion
Connector
kHz
1
2
MHz
Balun
5.1 Power Supply
5.1.1 Battery power
Pushbutton
The radio transceiver incorporates MAC hardware accelerators to handle all actions
concerning RF modulation/demodulation, signal processing, frame reception and
transmission. Further information about the radio transceiver and the microcontroller
are provided in the datasheet, see reference [1].
The RF front-end implementation was kept minimal by using a balun with integrated
filter. An antenna, provided with the RCB, has to be connected to the SMA connector.
All components are placed on one PCB side to demonstrate a low cost manufacturing
solution.
The RCB is powered by a single supply voltage in the range of 1.8 V – 3.6 V, which
makes it possible to use 1.5 V alkaline cells. Optionally, the power can be supplied
from a base board. In this case the power switch SW1 must be in OFF position or the
battery has to be removed from the battery holder.
All PCB components are supplied by this single supply to minimize the bill of material
(BoM) and maximize the power efficiency.
For autonomous operation, the RCB can be supplied by two AAA batteries to be
inserted in the battery clip on the back side of the RCB. Use power switch SW1 to
manually switch on/off the board. Note, a power cycle may not be detected if radio
transceiver and microcontroller are in sleep mode, and all periphery disabled.
LEDs
EEPROM
5.1.2 External power
5.2 Microcontroller
6
An RCB mounted on a base board may be powered via the expansion connectors,
see Table 5-2. In this case the power switch SW1 has to be in OFF position to avoid
unintentionally charging of the batteries, if they are applied.
The ATmega128RFA1 integrates a low-power 8-bit microcontroller based on the AVR
enhanced RISC architecture. The non-volatile flash program memory of 128 kB and
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16 kB of internal SRAM, supported by a rich set of peripheral units, makes it suitable
for a full function sensor network node.
The microcontroller is capable of operating as a PAN-coordinator, a full function
device (FFD) as well as a reduced function device (RFD), as defined by
IEEE802.15.4 [2]. However, the RCB is not limited to this and can be programmed to
operate in other standards or ISM applications, too.
All spare I/O pins are accessible via the expansion connectors for external use.
The ATmega128RFA1 is designed to operate at full 16 MHz speed over the complete
supply voltage range from 1.8V to 3.6V.
5.3 On Chip Radio Transceiver
Beside an 8-bit AVR microcontroller, the ATmega128RFA1 further integrates an
IEEE802.15.4 compliant radio transceiver. RF and base band critical components are
integrated to transmit and receive signals according to IEEE802.15.4, or even
proprietary ISM data rates.
The RCB illustrates a minimal component count implementation. Filter-balun B1 [6]
operates as a differential to single ended converter connecting the ATmega128RFA1
to a standard SMA connector. An integrated harmonic filter ensures sufficient
harmonic rejection.
A 2.45 GHz ISM antenna shall be connected to the SMA connector for proper
operation.
Any modification of components, PCB layout and shielding may influence the
performance of the circuitry and cause existing certifications to be invalid.
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5.4 Clock Sources
5.4.1 Radio Transceiver clock
5.4.2 Microcontroller
The integrated radio transceiver is clocked by a high accurate 16 MHz reference
crystal Q2. Operating the node according to IEEE802.15.4, the reference frequency
deviation must be within +/-40 ppm, see [2]. The absolute clock frequency is mainly
determined by the external load capacitance of the crystal, which depends on the
crystal type and is given in its datasheet.
The radio transceiver reference crystal Q2 shall be isolated from fast switching digital
signals and surrounded by a grounded guard trace to minimize disturbances of the
oscillation.
The RCB uses a SIWARD crystal SX4025 with two load capacitors of 10 pF. To
compensate fabrication and environment variations the frequency can be tuned with
the transceiver register “XOSC_CTRL (0x12)”, refer to [1], section 9.6. An initial
tuning is done during fabrication and the correction value has been stored in the
onboard ID-EEPROM, see section 5.5.2.
By setting the fuses accordingly, the microcontroller can also be clocked by the
16 MHz radio reference crystal.
There are various clock source options for the microcontroller inside the
ATmega128RFA1:
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5.5 On-Board Peripherals
5.5.1 Key & LED’s
• 16 MHz calibrated internal RC oscillator
• 128 kHz internal RC oscillator
• 16 MHz radio reference crystal
The calibrated internal RC oscillator, prescaled to 8 MHz is used as the default
clocking. It is recommended to use the MAC symbol counter, see [1], clocked from
the 16 MHz radio crystal, as a reference to calibrate the RC oscillator for higher
accuracy.
The symbol counter replaces and enhances the CLKM driven timer1 function,
originally available in ATmega1281V based solutions.
A 32 kHz crystal Q1 is connected to the related ATmega128RFA1 pins (17-TOSC2;
18-TOSC1) to be used as a low power real time clock. This time base can also run in
sleep mode and create timer based system wake-up events.
For simple applications, debugging purposes or just to deliver status information, a
basic user interface is provided directly on-board, consisting of four LED’s and a
pushbutton. Three LED’s (D2…D4) are connected to PE2…PE4 for active low
operation; one LED (D5) signals the single chip reset state. The pushbutton (T1) pulls
PE5 to GND, intended to be used in combination with the internal pull-up resistor.
When mounted on a base board, I/O ports PE4 and PE5 are used to emulate #WR
and #RD lines handling a memory interface. Therefore the pushbutton and LED D4
are not functional. On RCB128RFA1 the port G I/O lines can not be used since they
are shared with dedicated radio transceiver functionality.
In sleep, when the signals are supposed to be inactive, no additional current occurs.
5.5.2 ID-EEPROM
8
Figure 5-2. RCB128RFA1 Key and LED Connection
Firmware based board type identification is supported by an optional identification
EEPROM. Information about the RCB itself, MAC addresses and production
calibration data are stored. An Atmel AT25010A EEPROM [7] with 128x8 bit
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organization and SPI interface is used because of its small package, low voltage and
low power operation.
Compared to Atmega1281V based RCB’s, the ID-EEPROM interface has been
designed in a different way. Accessing the ID-EEPROM requires PG5 set to logic low.
This pin is not used on Atmega1281V based RCB’s, refer to Figure 5-3 for details.
Figure 5-3. ID-EEPROM Access Decoding Logic
The ID-EEPROM data is written during board production test with
• A unique serial number,
• MAC address
• Calibration values.
Calibration values are to be used to optimize radio transceiver performance.
Final products do not require this external ID-EEPROM functionality. All data can
directly be stored in the Atmega128RFA1 internal EEPROM. The ID-EEPROM is
placed for convenience, to simplify microcontroller firmware development.
Table 5-1 shows the data structure of the ID-EEPROM. The Cal RC values can be
used as a start value for the RC calibration algorithm. The Cal OSC 16 MHz value
can simply be copied to the corresponding radio transceiver register to reduce the
frequency deviation. However, the 16 MHz crystal is guarantied to deviate less than
20 ppm at room temperature, from the actual 16 MHz value without any calibration
adjustment. When the Cal OSC 16 MHz value is applied, the deviation is less than
5 ppm at room temperature.
Table 5-1 ID-EEPROM Mapping
Address Name Type Description
0x00 MAC address uint64 MAC address1 for the 802.15.4 node,
little endian byte order
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Address Name Type Description
0x08 Serial Number uint64 Board serial number, little endian byte order
0x10 Board Family uint8 Internal board family identifier
0x11 Revision uint8 Board revision number eg. 06 03 01
0x14 Feature uint8 Board features, coded into 7 Bits
7 Reserved
6 Reserved
5 External LNA
4 External PA
3 Reserved
2 Diversity
1 Antenna
0 SMA connector
0x15 Cal OSC 16 MHz uint8 RF231 XTAL calibration value, register
“XTAL_TRIM”
0x16 Cal RC 3.6 V uint8 AVR internal RC oscillator calibration value
@ 3.6 V, register “OSCCAL”
0x17 Cal RC 2.0 V uint8 AVR internal RC oscillator calibration value
@ 2.0 V, register “OSCCAL”
0x18 Antenna Gain int8 Antenna gain [resolution 1/10 dBi]
eg.: 0x0A = 10d will indicate a gain of 1.0dBi.
The values 00h and FFh are per definition invalid.
Zero or -0.1dBi has to be indicated as 0x01 or
0xFE.
0x20 Board Name char[30] Textual board description
0x3E CRC uint16 16 Bit CRC checksum, standard ITU-T generator
1
Note: MAC addresses used for this package are Atmel property. The use of these
polynomial G16(x) = x16+x12+x5+1
MAC addresses for development purposes is permitted.
Example ID-EEPROM dump:
6D 4D 17 FF FF 25 04 00 86 12 00 00 2F 00 00 00 mM...%....../...
01 06 03 01 02 00 A5 A5 01 FF FF FF FF FF FF FF ................
52 43 42 31 32 38 52 46 41 31 00 00 00 00 00 00 RCB128RFA1......
00 00 00 00 00 00 00 00 00 00 00 00 00 00 52 F2 ..............R.
FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ................
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