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AC4868 868 MHz Transceiver

User’s Manual

Americas: +1-800-492-2320 Option 3

17

Laird Technologies

Europe: +44-1628-858-940

Hong Kong: +852 2923 0610

www.lairdtech.com/ramp

Max Power

Max Power provides a means for controlling the RF output power of the AC4868. Output power and current
consumption can vary by as much as ±10% per transceiver for a particular Max Power setting. Contact Laird
Technologies for assistance in adjusting Max Power.

Engineer’s Tip: The max power is set during Production and may vary slightly from one transceiver to

another. The max power can be set as low as desired but should not be set above the original
factory setting. A backup of the original power setting is stored in EEPROM address 0x8E.

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Summary of Contents for AC4868

Page 1: ...Americas 1 800 492 2320 Option 3 Europe 44 1628 858 940 Hong Kong 852 2268 6567 x026 www lairdtech com ramp AC4868 868 MHz Transceiver User s Guide Version 2 0 ...

Page 2: ...ber 2005 Added Declaration of Conformity 1 2 29 May 2007 Updated serial interface section Corrected EEPROM write command response 1 3 18 September 2007 Internal Release 1 4 5 September 2008 Updated to Laird Technologies branding Clarified Duty Cycle calculations Updated information on client to client communications Corrected Read Temperature Command to a max of 0x50 Updated Minimum Baud Rate 2 0 ...

Page 3: ...gulations 11 Radio Operation 11 Transmit Calculations 11 Serial Interface 12 Serial Communications 12 Asynchronous Operation 12 Parity 12 OEM Host Data Rate 13 Serial Interface Baud Rate 13 Interface Timeout RF Packet Size 13 Flow Control 14 Half Duplex Full Duplex 14 System Timing and Latency 15 System Throughput 15 Software Interface 16 Networking 16 Range Refresh 16 Auto Config Parameters 16 Ma...

Page 4: ...DC 27 Write Digital Outputs 27 Write DAC 27 Set Max Power 28 Transmit Buffer Empty 28 Deep Sleep Mode 28 Read Temperature 28 EEPROM Byte Read 28 EEPROM Byte Write 29 Reset 29 EEPROM Parameters 30 Dimensions 33 Mechanical Drawings 33 Ordering Information 34 Product Part Number Tree 34 Developer Kit Part Numbers 34 Compliancy Information 35 Agency Identification Numbers 35 Approved Antenna List 35 O...

Page 5: ...io can be configured as a Server to provide a synchronization beacon This beacon is used by the Client radios to determine In Range status and for Auto Destination addressing This document contains information about the hardware and software interface between a Laird Technologies AC4868 250 transceiver and an OEM Host Information includes the theory of operation specifications interface definition...

Page 6: ... encryption key Interface Buffer size Input Output 256 bytes each Physical Dimensions Transceiver with MMCX Connector 1 65 x 1 9 x 0 20 Table 2 Transceiver Specifications Parameter Description Frequency Band Europe 500 mW 869 4 869 65 MHz RF Data Rate 19 2 kbps or 28 8 kbps dependent on interface baud rate RF Technology Single Frequency FSK Output Power Conducted no antenna EIRP 2 5 dBi gain anten...

Page 7: ...eiver I O RS485 B Invert Mirror image of RS 485 A 4 I GI0 Generic Input pin 5 16 GND GND Signal Ground 6 N C This pin has an internal connection and should be left disconnected 7 O CTS Clear to Send Active Low when the transceiver is ready to accept data for transmission 8 I RTS Request to Send When enabled in EEPROM the OEM Host can take this High when it is not ready to accept data from the tran...

Page 8: ... pin has an internal connection and should be left disconnected 14 I GI1 Generic Input pin 15 I UP_RESET RESET Controlled by the AC4868 250 for power on reset if left unconnected After a stable power on reset a logic High pulse will reset the transceiver 17 I CMD Data When logic Low the transceiver interprets OEM Host data as command data When logic High the transceiver interprets OEM Host data as...

Page 9: ...ed Addressed Packets When sending an addressed packet the RF packet is sent only to the receiver specified in destination address To increase the odds of successful delivery Transmit retries are utilized transparent to the OEM Host the sending radio will send the RF packet to the intended receiver If the receiver receives the packet free of errors it will return an RF acknowledge within the same 5...

Page 10: ...gies Europe 44 1628 858 940 Hong Kong 852 2923 0610 www lairdtech com ramp Command Mode command Once in Command Mode all data received by the radio is interpreted as command data Command Data can be either EEPROM Configuration or On The Fly commands Figure 1 Pending RF and Data in Buffer Flow ...

Page 11: ... data whenever data is present on the serial UART Data will be transmitted for Broadcast packets according to the value of the Broadcast Attempts For Addressed Packets data will be transmitted until a successful acknowledgement is received The OEM is responsible for limiting the Transmitter s on time to less than the duty cycle regulations Transmit Calculations For a rough estimate the TX Time on ...

Page 12: ...g with the transmitter This is achieved by having a fixed baud rate and by using START and STOP bits A typical asynchronous mode signal is shown below Figure 2 Asynchronous Mode Signal The UART outputs and inputs logic level signals on the TX and RX pins The signal is high when no data is being transmitted and goes low when transmission begins The signal stays low for the duration of the START bit...

Page 13: ... not supported For a baud rate to be valid the calculated baud rate must be within 3 of the OEM Host baud rate If the Test pin Pin 12 is pulled logic Low at reset the baud rate is forced to 9600 Baud BaudL 0x42 BaudH 0x43 RF Baud not adjustable Minimum Interface Timeout 0x58 Stop Bit Delay 0x3F 57600 1 0xFC 0x00 28800 0x02 0x03 38400 0xFA 0x00 19200 0x02 0x08 28800 0xF8 0x00 28800 0x02 0x0E 19200 ...

Page 14: ...ce buffer is getting full Your hardware should stop sending at this point to avoid a buffer overrun and subsequent loss of data You can perform a successful design without monitoring CTS However you need to take into account the amount of latency the radio adds to the system any additional latency caused by Transmit Retries or Broadcast Attempts how often you send data non delivery network timeout...

Page 15: ... introduced in the system when considering high density applications In these cases we can just offer qualitative analysis of the latency in high density applications As the network load increases then the number of collisions that will occur increases As the number of collisions increase then the system latency increases As the distance between the transceivers increases so to does the system lat...

Page 16: ...t be set to a value of 1 To disable DES set bit 6 to a value of 0 The 7 byte 56 bits Encryption Decryption Key is located in EEPROM Bytes 0xD0 0xD6 Note It is highly recommended that this Key be changed from the default Range Refresh Range Refresh Range Refresh specifies the maximum amount of time a Client reports in range without having heard a beacon from the Server Each time the Client hears a ...

Page 17: ...tput power and current consumption can vary by as much as 10 per transceiver for a particular Max Power setting Contact Laird Technologies for assistance in adjusting Max Power Engineer s Tip The max power is set during Production and may vary slightly from one transceiver to another The max power can be set as low as desired but should not be set above the original factory setting A backup of the...

Page 18: ...Option 3 18 Laird Technologies Europe 44 1628 858 940 Hong Kong 852 2923 0610 www lairdtech com ramp TIMING DIAGRAMS AC 4868 250 Timing Diagrams Figure 4 Addressed Mode with Timeout Figure 5 Addressed Mode with Fixed Packet Length Figure 6 Broadcast Mode with Timeout ...

Page 19: ... 868 MHz Transceiver User s Manual Americas 1 800 492 2320 Option 3 19 Laird Technologies Europe 44 1628 858 940 Hong Kong 852 2923 0610 www lairdtech com ramp Figure 7 Broadcast mode with Fixed Packet Length ...

Page 20: ...ame Transitions logic Low at the start of a hop and transitions logic High at the completion of a hop The OEM Host is not required to monitor Hop Frame The AC4868 is a single frequency radio that uses fictitious hops though it generates a Hop Frame signal every time it transmits a timing beacon CTS The AC4868 250 has an interface buffer size of 256 bytes If the buffer fills up and more bytes are s...

Page 21: ...mode was intended for recovering transceivers from unknown settings and was not intended for use in real time communications UP_Reset UP_Reset provides a direct connection to the reset pin on the AC4868 250 microprocessor and is used to force a soft reset For a valid reset reset must be asserted High for a minimum of 11ms Command Data When logic High the transceiver interprets incoming OEM Host da...

Page 22: ...tion pin 17 of a transceiver must be asserted Low Software Configuration can be used by entering AT Command Mode before issuing the CC Commands Figure 8 AC5868 250 Configuration Flow AT Commands The AT Command mode implemented in the AC4868 250 creates a virtual version of the Command Data pin The Enter AT Command Mode Command asserts this virtual pin Low to signify Command Mode and the Exit AT Co...

Page 23: ...acket However if an RF packet is received before the Interface Timeout expires on a CC Command the transceiver will send the packet to the OEM Host before sending the CC Command response When an invalid command is sent the radio scans the command to see if it has a valid command followed by bytes not associated with the command in which case the radio discards the invalid bytes and accepts the com...

Page 24: ...ommand Mode Prior to sending this command the OEM Host must ensure that the transceiver s RF transmit buffer is empty If the buffer is not empty the radio will interpret the command as data and it will be sent over the RF This can be accomplished by waiting up to one second between the last packet and the AT command RF packet size must be set to minimum of 6 in order to send this command Command 0...

Page 25: ... for the In_Range line to go active Once this occurs the Client is in sync with the server and can be put back into power down mode Note This command is valid only for Client transceivers Command 0xCC 0x06 Bytes Returned 2 Response 0xCC Channel Sleep Walk Power Down Wake Up The OEM Host issues this command to bring the transceiver out of Power Down mode Command 0xCC 0x07 Bytes Returned 2 Response ...

Page 26: ...ree Least Significant Bytes of the MAC Address are used for packet delivery Command 0xCC 0x11 Bytes Returned 4 Response 0xCC MAC3 MAC2 MAC1 Parameters 0x00 0xFF corresponding to 3 LSBs of destination MAC Address Auto Destination The Host issues this command to change the Auto Destination setting When issuing this command the Auto Destination setting will only be changed if the corresponding enable...

Page 27: ...xCC 0x23 Data1 Bytes Returned 2 Response 0xCC Data1 Parameters Data1 bit 0 GO0 bit 1 GO1 Write DAC The OEM Host issues this command to write DA_Out to a particular voltage The transceiver uses a PWM Pulse Width Modulator to generate the analog voltage The theory behind a PWM is that a binary pulse is generated with a fixed duty cycle and rate As such this pin toggles between High Low This signal i...

Page 28: ... Bytes Returned 2 Response 0xCC 0x00 Deep Sleep Mode The OEM Host issues this command to put the transceiver into Deep Sleep mode Once in Deep Sleep mode the transceiver disables all RF communications and will not respond to any further commands until being reset or power cycled This command is valid for both Servers and Clients Command 0xCC 0x86 Bytes Returned 2 Response 0xCC Channel Read Tempera...

Page 29: ... writes of up to 128 bytes are allowed An EEPROM boundary exists between addresses 0x7F and 0x80 No single EEPROM write command shall write to addresses on both sides of that EEPROM boundary Command 0xCC 0xC0 Data1 Data2 Bytes Returned 4 Response 0xCC Data1 Data2 Data Parameters Data1 EEPROM Address Data2 Length 0x00 0x80 Data3 Last byte of data written Reset The OEM Host issues this command to pe...

Page 30: ... each transceiver should only transmit 10 of the time and beacons count as transmissions Range Refresh 0x3D 1 0x01 0xFF 0x18 Specifies the maximum amount of time a transceiver will report In Range without having heard a Server s beacon equal to hop period value Do not set to 0x00 Stop Bit Delay 0x3F 1 0x01 0xFF 0xFF For systems employing the RS 485 interface or Parity the serial stop bit might com...

Page 31: ... Configure values Interface Timeout 0x58 1 0x02 0xFF 0x04 Specifies a byte gap timeout used in conjunction with RF Packet Size to determine when a packet coming over the interface is complete 0 5 ms per increment RF Packet Size 0x5B 1 0x01 0xFF 0x24 Used in conjunction with Interface Timeout specifies the maximum size of an RF packet When Auto Config is enabled this value is overridden based on th...

Page 32: ... to communicate with each other RS 485 DE 0x7F 1 0xE3 0xFF 0xFF 0xE3 GO0 is active Low DE for control of external RS 485 hardware 0xFF Disable RS 485 DE MAC ID 0x80 6 0x00 0xFF Factory programmed unique IEEE MAC address Original Max Power 0x8E 1 Set in prod varies Copy of original max power EEPROM setting This address may be referenced but should not be modified Product ID 0x90 15 0x90 0x93 Produc...

Page 33: ...44 1628 858 940 Hong Kong 852 2923 0610 www lairdtech com ramp DIMENSIONS Mechanical Drawings Interface Connector 20 pin OEM Interface connector Molex 87759 0030 mates with Samtec SMM 110 02 S D MMCX Jack Antenna Connector Johnson Components 135 3711 822 Figure 9 AC4868 250 with MMCX connector Mechanical ...

Page 34: ...Numbers All of the above part numbers can be ordered as a development kit by prefacing the part number with SDK As an example part number AC4868 250M can be ordered as a development kit using the part number SDK AC4868 250M All developer s kits include 2 transceivers 2 development boards 2 7 5 VDC unregulated power supplies 2 serial cables 2 USB cables 2 antennas configuration testing software and...

Page 35: ...and still maintain compliance Table 13 AC4868 250 Approved Antennas Laird Part Manufacturer Part Manufacturer Type Gain dBi 200A 200M 1000M 0600 00020 S467 FL 6 RMM 868S Nearson Wave Dipole 2 X X OEM Equipment Labeling Requirements WARNING The OEM must ensure that the appropriate labeling requirements are met Following are the requirements for labeling equipment If the CE marking is reduced or enl...

Page 36: ...is responsible for ensuring that these restrictions are met RF Channel Country Restriction Reason Remarks 0x38 Al countries unless otherwise noted Maximum ERP of 500 mW and max transmit duty cycle of 10 amortized over one hour 0x38 Bulgaria Not implemented 0x38 Finland Audio and voice are not permitted 0x38 Germany Audio and voice are not permitted 0x38 Italy Maximum EIRP of 25mW Military applicat...

Page 37: ...ng 852 2923 0610 www lairdtech com ramp Declaration of Conformity Laird Technologies has issued a Declaration of Conformity for the AC4868 250M transceiver module concerning emissions EMC and safety The Declaration of Conformity is a document that lists the product name and band of use and must appear in the OEM user s manual ...

Page 38: ...and output capacitors to the bottom side ground plane If the input voltage will be less than 12 volts then C1 and C2 can be replaced with a single 100uF 20 volt capacitor same part number as C7 This will reduce board space and lower costs further If you are powering an AC5124 module R1 can be changed to a 373 ohm 1 resistor This will change the output to 5 volts at 1 0 amps Bill of Materials Qty R...

Page 39: ...AC4868 868 MHz Transceiver User s Manual Americas 1 800 492 2320 Option 3 39 Laird Technologies Europe 44 1628 858 940 Hong Kong 852 2923 0610 www lairdtech com ramp Schematic PCB Layout ...

Page 40: ...AC4868 868 MHz Transceiver User s Manual Americas 1 800 492 2320 Option 3 40 Laird Technologies Europe 44 1628 858 940 Hong Kong 852 2923 0610 www lairdtech com ramp ...

Page 41: ...vel Conversion ICs This is the easiest and most efficient method Laird Technologies recommends the TI SN74LVC244A Octal Buffer Driver Inputs can be driven from either 3 3 or 5V systems allowing the device to be used in a mixed 3 3 5V system Passive Resistor Voltage Divider While a resistor voltage divider can successfully drop the 5V to the required 3 3V it will draw static current all of the time...

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