Spot STX3 User Guide
Revision 1.0 STX3 Users Manual
STX3 Users Manual
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Revision 1.0 STX3 Users Manual
Table of Contents
1 Introduction .................................................................................................................................................................... 3
1.1 Purpose ................................................................................................................................................................... 3
1.2 Applicable Documents ............................................................................................................................................ 3
1.3 Description .............................................................................................................................................................. 3
2 Application ...................................................................................................................................................................... 4
2.1 Theory of Operation ................................................................................................................................................ 4
2.2 Block Diagram ......................................................................................................................................................... 6
3 Physical Charactersistics ................................................................................................................................................. 8
4 Application Programming Interface .............................................................................................................................. 11
4.1 Serial Port .............................................................................................................................................................. 11
4.2 Serial Packet Mode ............................................................................................................................................... 12
4.2.1 Serial Packet Format ..................................................................................................................................... 12
4.2.2 Serial Packet Commands ............................................................................................................................... 13
4.2.2.1 Send Data (0x00) ....................................................................................................................................... 13
4.2.2.2 Query Electronic Serial Number (ESN) (0x00) ........................................................................................... 13
4.2.2.3 Abort Transmission (0x03) ........................................................................................................................ 14
4.2.2.4 Query Bursts Remaining (0x04) ................................................................................................................ 14
4.2.2.5 Query Firmware Version (0x05) ................................................................................................................ 14
4.2.2.6 Setup (0x06) .............................................................................................................................................. 15
4.2.2.7 Query Setup (0x07) ................................................................................................................................... 15
4.2.2.8 Query Hardware Version (0x09) ............................................................................................................... 16
4.3 Example CRC calculation routines for serial packets ............................................................................................ 18
4.4 AT commands ........................................................................................................................................................ 20
5 Test Modes .................................................................................................................................................................... 23
6 REGULATORY APPROVAL .............................................................................................................................................. 25
6.1 Radio Astronomy Site Avoidance .......................................................................................................................... 25
6.2 Regulatory Notices ................................................................................................................................................ 25
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Revision 1.0 STX3 Users Manual
1 Introduction
1.1 Purpose
This document describes the physical, electrical, and functional characteristics of the STX3 satellite transmitter
module. The information contained in this document is intended to provide the end user with the necessary
technical information required to use the module in a custom application.
This document is intended to be used by engineers and technical management and assumes a general knowledge of
basic engineering practices by the user.
1.2 Applicable Documents
1.3 Description
The STX 3 is a simplex Satellite transmitter designed to send small packets of user defined data to a network of low
earth orbiting (LEO) satellites using the Globalstar simplex satellite network. The received data is then forwarded to
a user defined network interface that may be in the form of an FTP host or HTTP host where the user will interpret
the data for further processing.
The STX3 is a surface mount module designed to attach to a user defined host PCB which must provide power, an
RF connection to the transmit antenna, and communications with a host processor which will control the operation
of the STX3. All electrical connections are provided via the castellated pads on the perimeter of the PCB.
The STX3 is a small, low-profile device with the dimensions shown below.
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Figure 1 (dimensions in inches)
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The STX3 operates on the Globalstar LEO satellite network. LEO (Low Earth Orbit) means that there are a number of
satellites in low earth orbit that constantly orbit the planet and can communicate with Globalstar devices that are within
Since the satellite position is constantly changing, simplex devices on the ground will transmit (with no knowledge of
the transmission
gateway as shown below. Once received by the
simplex gateway where redundant messages are d
message is sent to the OEM via the Internet.
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d by one or more satellites. These satellites will then
satellite
iscarded and the data from the
2 Application
2.1 Theory of Operation
range of its current position.
STX3 Users Manual
any of the satellites locations) and
relay the message to the nearest satellite
message will be delivered to the
Figure 2 LEO Constellation
may be receive
gateway, the simplex
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byte payloads. The STX3 can only transmit 9
payloads greater than 9 bytes will require multiple on
e brief periods of time where there is no satellite in range of the simplex transmitters due to obstructions
satellite coverage geometry. Since a simplex device has no way of knowing if a transmitted message has been
device is designed to send
sent over the Globalstar network. The default value for the number of redundant
means that each message sent to the STX3 will be tr
The redundant transmissions
packet message using the default s
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air messages, so user
to be transmitted for each user payload.
for each message being
transmissions
ansmitted 3 times. Each transmission will contain the exact same
minute
etting of 3 redundant transmissions is shown
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Messages are composed of 1 or more 9-
There ar
and/or
successfully received, the STX3
Figure 3 Simplex Messaging
-air packets
multiple (redundant) transmissions
-byte on-
per message is 3. This
data payload.
The transmission sequence for a singlebelow.
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of each message will be sent on a randomized 5-
nominal interval.
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packet message using the default setting of 3 redundant transmissions is shown
For normal conditions where the transmitter has an open view of the sky, this will result in a better than 99% chance
The basic elements of a design utilizing the STX3 simplex transmitter are shown below.
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The transmission sequence for a twobelow.
STX3 Users Manual
that the message will be received.
2.2 Block Diagram
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The STX3 provides separate power supply inputs. The digital power supply input (VDIG) is a low power input which
powers the digital portion of the STX3. This provides the capability to leave the STX3 in a low power cons
when the transmitter RF section is idle. The RF power supply input is a high power input which is only required while the
Since the transmission duty cycle is very low, this supply may be turned off the
ajority of the time and only active during the transmission of a packet. Due to the random nature of the burst
transmissions, and open collector output (PWR_EN) is provided by the STX3 which can directly control the high current
ensure that the RF power supply is enabled for the
transmission. It may also be monitored by the host to determine when each burst has been completed without the
need to query the STX3 via the serial host interface
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amount of time to complete each
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STX3 is transmitting a data packet.
m
supply for VRF. This will
Figure 4
umption state
minimum
.
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3 Physical Charactersistics
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Figure 5 Top View
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Recommended PCB footprint layout (dimensions in inches)
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Figure 6
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