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| Supports Point to
Multi Point and Broadcast Mode Test |
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The SpacePort Modem Evaluation board
enables SPM / RPM to be transformed in to a complete Radio modem
with DCE type RS232 interface.
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Figure 1: SpacePort Modem Evaluation
Kit |
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Range of Features
- Direct interface
to RS232 serial port
- Onboard regulator
can provide 5V, 1A supply to power-up DTE (e.g. barcode scanner)
- Visual indications
of operation through LEDs
- Access to internal
diagnostic/Test modes using HyperTerminal
- Access to each data/control
pins for external interface or testing
- Set-up and configuration
using HyperTerminal
- Built-in command
line configuration
- PP3 9V battery powered.
DC jack and terminal block provided for external supply
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Kit Contents
The SPM Evaluation Kit comes with the following
contentes:
2 SPM Evaluation Board1
2 SPM/RPM modules (ordered separately)
2 9V battery (PP3)
2 1/4 wavelength whip antenna2
4 Jumpers
1 SPM data sheet
1 SPM Eval-Kit data sheet
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Visual Facilities
The following status LEDs will be activated
depending on the SPM operation mode.
| LED |
Indication |
| TX (Red) |
Transmitter enabled |
| RX (Green) |
Receiver enabled; ; blinks
in Auto standby mode |
| SIGNAL (bright Red) |
Preamble detected |
| OK (bright Yellow) |
Valid packet received / Test
passed |
| Power (Green) |
Power Supply on |
Notes:
1. The standard SPM evaluation kit comes with 2 Evaluation Board.
In order to test the point to multipoint and broadcast modes of
the SPM, at least 3 Evaluation Board would be required.
2. BNC connector can be replaced with SMB connector or terminal
block to use different antenna connection
Additional requirements
1. DB9M - DB9F straight through serial
cable
2. External power supply or DC power adaptor (optional)
3. PC/PDA with terminal program (e.g. Hilgraeve HyperTerminal)
On-board regulator (LM340TS) can supply up
to 1A current at 5V. The 5V supply line is connected to the pin
9 (Ring Indicator) of DB9F connector which enables any external
host to be powered from pin 9 (+5V DC) and pin 5 (GND). Certain
CCD barcode scanner can make use of this feature, eliminating
the need for additional external power adaptor.
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Serial Pin
outs - RS232 (EIA/TIA-574) and RS232D (EIA/TIA-561)
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Figure 2: DB9 Serial Port
pin label
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DB9 |
DB25 |
Pin function |
SPM Eval Kit (DCE) |
Host (DTE) |
| 1 |
8 |
Data Carrier Detect |
Output |
Input |
| 2 |
3 |
Receive Data |
Output |
Input |
| 3 |
2 |
Transmit Data |
Input |
Output |
| 4 |
20 |
Data Terminal Ready |
Input |
Output |
| 5 |
7 |
Signal Ground |
- |
- |
| 6 |
6 |
Data Set Ready |
Output |
Input |
| 7 |
4 |
Request To Sent |
Input |
Output |
| 8 |
5 |
Clear To Sent |
Output |
Input |
| 9 |
22 |
Ring Indicator |
+5V DC |
Input |
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| In certain
applications a DB9M to RJ45 adaptor cable will be required to interface
SPM to Host. e.g. barcode scanners. |
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Figure 3: RJ45 Male and
Female connectors
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Pin No |
Name |
Notes/Description |
| 1 |
DSR/RI |
Data Set Ready/Ring
Indicator |
| 2 |
DCD |
Data Carrier Detect |
| 3 |
DTR |
Data Terminal Ready |
| 4 |
SGND |
Signal Ground |
| 5 |
RD |
Receive Data |
| 6 |
TD |
Transmit Data |
| 7 |
CTS |
Clear To Send |
| 8 |
RTS |
Request To Send |
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| Interfacing SPM Evaluation
Kit to Data Terminal Equipment (DTE) |
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Figure 4: DB9M-DB9F straight through modem
cable
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Figure 5: DB9M-DB25F straight through
modem cable
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The SPM Eval board interface is a 9 way
female D type connector. The CTS, DSR and DCD are wired
together eliminating the need for special RS232 cables in
certain DTE interface configurations.
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using SPM Eval Kit with DTE (e.g. printer and printer driver) which
uses DTR/DSR flow control instead of RTS/CTS flow control, the shut
down mode should be disabled in configuration by turning SHDN to
OFF.
SPM implements DTE to DCE flow control using
CTS line. CTS is wired together with DSR and DCD in the Evaluation
Kit to meet common DTE interface requirement. However, SPM does
not implement DCE to DTE flow control using RTS line. DTR line
used to wake up the module if SHDN is turned ON and put it to
sleep if the Host (DTE) is detached from SPM.
Therefore, if the receiving DTE(B) [e.g.
EPoS printer] cannot process [print] received data fast enough,
DTE(B) will not be able to stop attached SPM(B) from sending any
further data which SPM(B) received from SPM(A). SPM(A) will assume
SPM(B) is ready to receive more data every time SPM(B) sends back
a packet acknowledgements as SPM buffers are not filled to stop
DTE. DTE(A) [PC] will continue to send more data resulting in
data corruption in DTE(B). Simple solution is to reduce the baud
rate (e.g. 2,400bps) between SPM(A) and DTE(A) and use maximum
possible baud rate (e.g. 9,600bps) between DTE(B) and SPM(B).
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| Interfacing SPM Evaluation
Kit to Data Communications Equipment (DCE) |
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Figure 6: DB9M-DB9M null-modem cable
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Figure 7: DB9M-DB9M null-modem cable
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SPM Configuration
To configure the SPM the HyperTerminal should be set with the
following settings. ASCII Setup should be left at default settings
with no ticks on Send line ends with line feeds and Append line
feeds to incoming line ends.
Hardware flow control should be disabled. Default baud rate of
the SPM is 9600bps. However if the default baud rate of the SPM
is changed then the baud rate of the HyperTerminal should be matched
or DEFAULT jumper should be connected to force the SPM baud rate
to 9600bps.
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Figure 8: Serial port setting on HyperTerminal
to configure SPM
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| SPM has a 2mm pitch
pin-out for embedded system applications where PCB space is very
limited. However, for the convenience of evaluating the module,
a separate row of 0.1" pitch pin headers are provided on both
side of the SPM sockets. |
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| Oscilloscope
probes can be easily connected on these to monitor data transmission
on each stage from serial RS232 type data entering SPM, FRPC transmitting
packetised data, SPM on receiving end sending serial data to attached
Host and sending back Packet Acknowledgements.
Oscilloscope screen capture below were taken
during a large file transfer at 115,200bps using HyperTerminal
with ZMODEM setting. They were captured on Laptop from Tektronix
TDS2024 Digital Storage Oscilloscope fitted with TDS2CM Communications
Extension Module. The wireless RS232 link was established using
SPM Evaluation Kit with SPM2-433-28.
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Figure 9: Serial RS232 data transmission and
reception with hardware flow control
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TXD-RS232 is the inverted RS232 data at TTL
level entering the SPM module at 115,200bps.
RPM sends the collected data bytes with necessary
site, unit and other control information bytes to FRPC. CTS flow
control is set high when the SPM buffer reaches about 66% full,
to prevent attached PC from sending further data bytes.
FRPC packetises all the bytes from RPM with
preamble, synch byte, check sum and encodes each 8 bit byte into
a 12 bit code for reliable transmission over the radio. TXD/AF
trace is the packetised data transmission from FRPC to TXD pin
of radio transceiver within the SPM module.
RXD-RS232 is the received inverted RS232 data
at TTL level sent by SPM to attached host PC. It can be seen from
the trace that the RS232 data stream coming into SPM is broken
into two parts and transmitted as two packets.
SPM will not transmit the next packet until
an acknowledgement for the previously transmitted packet is received
if the ACKMODE is switched ON as shown in the following oscilloscope
screen capture.
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Figure 10: Serial RS232 data transmission with
packet acknowledgement
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the ACKMODE OFF, the overall data throughput can be increased up
to 55kbps with SPM2-433-28. In this fast mode, SPM(A) will not wait
for a packet acknowledgement from SPM(B). |
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Figure 11: File transfer with ACKMODE
ON
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Figure 12: File transfer with ACKMODE
OFF
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broadcast mode, same data/file can be transferred to several hosts
attached to SPM Eval Kits at the same time. ACKMODE is should also
be turned OFF in broadcast mode otherwise the acknowledgements from
multiple slave SPMs will cause master SPM hang up.
Usually point-to-multipoint communication is
used by a host (e.g. microcontroller) which can pull the SETUP
line low and send the command ADDR [new unit address] to change
address dynamically to communicate with several other hosts by
addressing them individually. This can be simulated in Evaluation
Kit by inserting SETUP jumper and typing the new dynamic unit
address using HyperTerminal with its flow control disabled.
The SETUP jumper should be removed before pressing
the Carriage Return (0Dhex) key. SPM will echo back with dot (2Ehex)
to confirm address change. If SETUP jumper is not removed, SPM
will remain in configuration mode. Flow control in HyperTerminal
should be set to HARDWARE for higher baud rate data transfer.
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Figure 13: Near continuous streaming of data
packets with ACKMODE OFF
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| SPM2-433-28
implements a very efficient data buffer management algorithm. In
most cases at low or default baud rates (e.g. 9600bps), it is capable
of transmitting continuous stream of serial data without asserting
CTS line (no flow control) as shown below and transmit the data
packets in short bursts with long gaps between RF transmission minimising
the air-time usage. |
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Figure 14: SPM2-433-28 receiving from DTE continuously
without asserting CTS at 9600bps
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Limitation of liability
The information furnished by Radiometrix Ltd
is believed to be accurate and reliable. Radiometrix Ltd reserves
the right to make changes or improvements in the design, specification
or manufacture of its subassembly products without notice. Radiometrix
Ltd does not assume any liability arising from the application
or use of any product or circuit described herein, nor for any
infringements of patents or other rights of third parties which
may result from the use of its products. This data sheet neither
states nor implies warranty of any kind, including fitness for
any particular application. These radio devices may be subject
to radio interference and may not function as intended if interference
is present. We do NOT recommend their use for life critical applications.
The Intrastat commodity code for all our modules is: 8542 6000.
R&TTE Directive
After 7 April 2001 the manufacturer can only
place finished product on the market under the provisions of the
R&TTE Directive. Equipment within the scope of the R&TTE
Directive may demonstrate compliance to the essential requirements
specified in Article 3 of the Directive, as appropriate to the
particular equipment.
Further details are available on The Office of Communications
(Ofcom) web site:
Licensing
policy manual
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