Telemetry

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All tracker models have the ability to send telemetry information from on board sensors, as well as external input sources.
Reporting options section from OTWINCFG

Some of the telemetry information can be embedded into the comment section of a packet, or you can configure the tracker to send separate packets in the APRS telemetry defined format.

T#sss,aaa,bbb,ccc,ddd,eee,76543210

"sss" is a sequence number which increments upon each telemetry report sent, wrapping at 999 back to 000. "aaa,bbb..." are analog values between 0 and 255. Their conversions are given in the table below. 0-7 are are binary bits, either 0 or 1. The currently active configuration profile may be reported as a telemetry bit.

A digital counter input is available on some tracker models. The counter value can be reported in status packets and in some models as a telemetry value.

For some models, the commands ANALOG and GPIO can be used to read specified analog inputs and read or set general-purpose digital I/O pins. The pin assignments for these commands are shown below.

Contents

Pin Assignments by Device

This information reflects current firmware versions and production hardware. Beta hardware and older firmware versions may have different assignments.

OT3m

Pin Function Value
Supply Voltage Telemetry aaa, ANALOG 0 Volts * 10 (Max 20v)
Terminal Block A1 Telemetry bbb, ANALOG 1 Volts * 10 (Max 20v)
Terminal Block A2 Telemetry ccc, ANALOG 2 Volts * 10 (Max 20v)
Terminal Block A3 Telemetry ddd, ANALOG 3 Volts * 10 (Max 20v)
Terminal Block A4 Telemetry eee, ANALOG 4 Volts * 10 (Max 20v)
Radio Pin 9 (AUX_IO) GPIO 0 ON = High, OFF = Low
Terminal Block IO Telemetry bit 1, GPIO 1, Profile Jumper ON = High, OFF = Low
Terminal Block CT Counter Input (if enabled) or Beacon Trigger Pull to ground to activate
Active Profile Telemetry bit 0 ON = Profile 2, OFF = Profile 1

OpenTracker USB

Pin Function Value
Supply Voltage Telemetry aaa, ANALOG 0 Volts * 10 (Max 20v)
CN4 Pin 3 Telemetry bbb, ANALOG 1 Volts * 10 (Max 20v)
CN4 Pin 4 Telemetry ccc, ANALOG 2 Volts * 10 (Max 20v)
CN4 Pin 5 Telemetry ddd, ANALOG 3 Volts * 10 (Max 20v)
CN4 Pin 6 Telemetry eee, ANALOG 4 Volts * 10 (Max 20v)
Radio Pin 9 (AUX_IO) GPIO 0, Power Relay ON = High, OFF = Low
CN4 Pin 7 Telemetry bit 1, GPIO 1, Profile Jumper ON = High, OFF = Low
Active Profile Telemetry bit 0 ON = Profile 2, OFF = Profile 1

OT2m Telemetry elements

Entry # Description Sensor input
aaa Temperature as reported by an on board LM335D sensor. (U5)
LM335D temperature sensor chip
bbb Source voltage being provided to the OT2m, measured by a voltage divider. (R16 / R17)
Voltage divider circuit
ccc Read from pin 10 (PTA0/ADC0) on the MON08 header on the circuit board. Allowable voltage input range is between 0 and 5 volts.
MON08 header
ddd Counter value, with the counter input on pin 1 (IRQ1) of the accessory port, also available from pin 6 (IRQ/counter/transmit-now input) on the MON08 header on the circuit board. Counter can be incremented by grounding this input. Software debounce settings are available.
Accessory Port
eee HDOP value reported by an attached GPS.
xxxxxxxx Only the last 2 binary bits are used on the OT2m.

Bit 7 reports the current status of the jumper input located on pin 6 (CFG) of the accessory port. Grounding this input reports a bit state of 1.

Bit 8 reports the current profile in use.

T3-301 Telemetry elements (UNDER CONSTRUCTION)

Entry # Description Sensor input
aaa
bbb
ccc
ddd
eee
xxxxxxxx

MON08 pinout

1 - PTB7/T2CH1 (digital I/O or timer channel)
2 - GND
3 - PTB5/T1CH1
4 - Reset
5 - No connection
6 - IRQ (counter/transmit-now input)
7 - No connection
8 - PTA3/ADC3 (digital I/O or ADC input)
9 - No connection
10 - PTA0/ADC0
11 - No connection
12 - PTA2/ADC2
13 - Clock oscillator (32.768 kHz)
14 - PTA1/ADC1
15 - +5V
16 - PTB0 (digital I/O)
MON08 header

Telemetry Equations, Units, Parameters, and Labels

APRS telemetry reports contain only raw values, and it is up to the user interface software to display the information in a human readable format, with appropriate calculations performed to provide corrected values.

In order to do this, the software needs to have some information provided to it so that it can do the appropriate conversions, display each value with the required units, properly labelled.

There are 4 sentences that provide this required information.


  • A Parameter Name message.

PARM.Temp.,Bat.,Extrn,Count,HDOP,NA,NA,NA,NA,NA,NA,JU,CF

The original DosAPRS program was limited to 80 characters per line, and to fit those limits, arbitrary parameter name lengths were chosen. If you wish to stay compatible with DosAPRS, the paramater name lengths for the 5 analog channels are 7, 6, 5, 5 and 4 characters. The lengths for the 8 digital bits are 5, 4, 3, 3, 3, 2, 2, and 2 characters respectively.

  • A Unit/Label message.

UNIT.Deg.,Volts,NUM,NUM,HDOP,,,,,,,ON,NUM

Sets the labels associated with the analog values, and for the digital bits, a label to association with the digital state.

  • An Equation Coefficients message.

EQNS.0,1.9608,-273,0,0.07843,0,0,0,0,0,0,0,0,0,0

There are three coefficients for each analog channel, a,b,and c. These three coefficients get plugged into a quadratic equation along with the reported analog value x. The result is calculated from this equation where FINAL VALUE = a*x^2 + b*x + c

  • A Bit Sense/Project Name message.

BITS.11111111,Your Telemetry Name

BITS format specifies which bit state is associated with the label. You can also specify a title for your telemetry page.

APRS telemetry definition sentences simply need to be sent to the target callsign as an APRS message.

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