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Telemetry with Graupner HoTT

AutoQuad with the HoTT extensions in the firmware will maximize the telemetry features. Most of the AutoQuad sensor data is able to transmit directly to a graupner HoTT transmitter.

2014-03-15 10.18.54-2

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  • HoTT enabled AutoQuad firmware
  • HoTT receiver (since r403 TELEMETRY_HOTT can be set to 0 so a HoTT receiver is no longer mandatory for the firmware extra’s). Please make sure both the transmitter and all receivers are up to date with the graupner firmware! As a minimum oct 2013!
  • Free serial port on the AutoQuad like with the DIMU board on an AQ6 board (uart2 available)

When using a DIMU board the GND, 5V and TX line is all you need to power the receiver and enable the telemetry. If you already have the receiver powered from another source you only need the TX line. Don´t power the receiver twice! Look in the appropriate Graupner manuals how to enable telemetry on the receiver, which port to select and how to enable telemetry reception on the transmitter.


Flash the firmware (Download section, experimental firmware release)
Connect all the cabling, power on the transmitter and WITHIN 20 sec turn on the AutoQuad FC with receiver.
If you’re too late not all sensors will show up on the transmitter (that is by design in Graupners protocol). Just power cycle the transmitter in that case.

Once all done, you can now toggle between all available ‘sensor’ screens using the up-down buttons.
Any AutoQuad flightcontroller will now output General Air module, Electric Air module, GPS and Vario sensors.

Binary telemetry / text telemetry

The HoTT protocol supports two types of telemetry, binary (default) and text.
Binary telemetry uses pre-defined screens and values, is very fast and supports datalogging to the internal uSD card in the HoTT transmitter.
Text telemetry is basically sending a 8×21 character text screen, it can be anything you want. The flexibility however does not support datalogging. It opens whole new possibilities in telemetry and most of the development is in this area.

Jump to the section by clicking on the telemetry type.

Binary telemetry

This section handles the Binary telemetry that is available. All HoTT available sensors (Electric Air Module, General Air module, Vario, GPS) are emulated and populated with all telemetry data from the AutoQuad flightcontroller.
Just use the up/down keys to select the module you’re interested in and with next/previous select the sensor data screen or just the overview screen with a selection of the most useful data


The main screen, (not available in General Air module) will also show the status line with information about the status.

As extra bonus all data will now be logged to the transmitter sd card (when you enable a flight timer as in the graupner manuals) and can be examined offline using the graupner logdata tools.

Replay the flight including the overlay on google maps is possible in that tool.

ESC32 telemetry
If the FW finds active CAN enabled ESC32’s, it will also show the AIR ESC module.
With the next-prev buttons you can walk through all available pages within a module.

Text telemetry

This is the most flexible option and there is even support for sending the transmitter buttons back to the AutoQuad making it a ‘Text based ground control station’

note: this is the firmware with an older menu, the new version is display here.

Note: When you enter the text menu’s the Transmitter logging to sd feature is disabled. That is because no predefined data is available and free format text cannot be logged obviously.

For AutoQuad a very special menu is build ‘hidden’ away in the transmitter screens. It is basically an 8×21 text screen that is transmitted. It is slower due to the size to transmit compared to the binary telemetry but the flexibility is enormous.

The text screen is reachable when you press ‘n hold the ‘ESC’ key on the transmitter until the telemetry menu appears. (only when the receiver is enabled for telemetry and receives data)

When you select ‘Settings & Data view’ en press enter/set you will enter the receiver text setup. Depending on the type of receiver (light version or normal) you need to press next (up to 6x) until the AutoQuad HoTT text menu screens.
In the current release a Main Menu is the first screen.

The menu items are self explanatory. For the main flight status with all the mission information select flight status with the up/d

Screen 1: Main overview: Battery, Capacity, GPS info, altitude, speed, home distance and status.

When going into mission mode all mission info including distance next waypoint, number of waypoints, actual waypoint type (goto pos, orbit, landing, takeoff  etc) and waypoint altitude is also displayed.
Also warnings like Ceiling (max altitude) reached is displayed.


Waypoint editor in edit mode

Waypoint editor in browse mode

Screen 2: Waypoint editor.
Any recorded waypoint (with WP recording switch) or uploaded waypoints are in this list and can be edited. Changing waypoint type, altitude, point of interrest etc. For edit press the set/enter key on the transmitter.

Press next for the extra menu (global waypoint edit)
In this menu you can change the altitude and/or horizontal speed for ALL waypoints. It is a offset, so the value is added to the original waypoint and is than 0 again in this menu.
Example: to increase all waypoint altitudes with 10m, just set the alt in this menu on 10 and press set/enter.
Extra: When an uSD is detected in the AutoQuad flightcontroller, the import / export waypoint function is enabled and shown.
You can now save all waypoints to the uSD card and later retrieve it using the import function.
Press set/enter to enable the edit function, press next to select either import / export and press set/enter again.

New mission type; JUMP TO :  Special for HoTT (not yet supported in QGCS or android app). With this misison type you can jump to a specific waypoint number for a (repeat) number of times. Example: make a mission to fly a square, for waypoints for the corner, a 5th for jump to. Set the jump to, to the 1st corner and the number of repeats. After the repeats the mission continues with the next waypoint for example land.

Screen 3, 4 & 5: Now it becomes fun: Settings.
Yes, you can change a selective set of AutoQuad parameters directly on the transmitter.

Next button / switch:  in edit mode: walk to next param.
Not in edit mode: next screen
Prev button:  not in edit mode and no menu switch assigned: main menu, with switch assigned: previous screen.
In edit mode: exit edit mode without save
Set button:     Enter edit mode. !only possible when disarmed!
In edit mode: save params if any params are changed and exit.
Up button:     In edit mode: increase value selected param
Not in edit mode: previous param
Down button: In edit mode: decrease value selected param
Not in edit mode: next param

The most used params needed for tuning in the field are available. If needed you can always leave a suggestion in the forum for other params.

Please note that every cursor move or data transmit will take up to 0.5s. If cursors or screens will not react on the buttons check what kind of text screen is selected. That can be done using the left button pad up down keys. The cursors will act on general, electric, receiver and etc screens. (by default when the transmitter is powered on and received the first textscreen)

Screen 6: Only available with CAN bus enabled ESC32’s
All found and active ESC32 RPM and Wh usage.
When you press Set(in Disarmed status) you enter an extra utility and info mode

Set button:    Enter Info mode.
Next button:  walk to next ESC32, the inverted arrow points to the selected Esc32
Prev button:  exit info mode or back to screen 1
Up button:     Ping (send beep command) to selected Esc32. You can identify the esc32 and motor with this option.
The statusline displays the selected Esc32 max Amps, the temp (not yet available) and disarm (error) code.

Screen 7: AutoQuad info
This screen shows a collection of gathered information about the Flightcontroller hardware (AQ6, AQ7 or M4), the ESCs, the firmware versions, the ESC connection (CAN/PWM)
uSD card: when a uSD is detected the current log file is displayed and the free space on the uSD
Tools: press set/enter to select the tool menu, reboot will reboot the autoQuad flightcontroller (only if disarmed) and log will enable/disable logging to uSD. Reboot will require a confirmation, just follow the on screen suggestions.

Firmware extra’s

  • Waypoint recording. Using a defined switch (NAV_WPREC_CHAN) in params, waypoints can be recorded during any stage, armed, disarmed, during flight etc. It will increase the number (and display them on the HoTT screens) with every switch trigger (>1 sec)
  • Currentsensor support, using the pressure2 pads on a AQ6 board, current sens is supported and displayed in all HoTT screens as capacity used and actual current.
  • Armed safety timeout. If you arm and forget, this firmware will warn after 30 seconds (using signaling) and disarm after another 10 seconds. Flying disables the watchdog timer.
  • GeoFence. You can set a defined horizontal circle around the home position (in meters). When close to breaching a warning message is displayed. When breached the user controls (pitch/roll) will fall back to 10%. Its like hitting a wall. Returning inside the wall will restore the controls to full scale. Return to Home will work.Param is NAV_SIMPLE_FENCE set in meters.
  • Now also non HoTT users can use the firmware extra’s. Set TELEMETRY_HOTT to 0 and the telemetry part will not be initialized.

HoTT firmware parameters explained

TELEMETRY_HOTT Set to 0 to disable HoTT, any higher for protocol delay (800 is default)
TELEMETRY_LOG Enable AutoQuad log (1 default) or disable (0)
RADIO_HOTT_CH Option: channel for next key (<0.5s) or main menu (>0.5s)
NAV_WPREC_CHAN Option: Waypoint recording channel switch
DIMU_PROM_EN Enable (1 default) DIMU EEProm read DIMU params, you can switch between AutoQuad flash stored params (0) and DIMU stored params (1)
NAV_SIMPLEFENCE Option: GeoFence around home in meters (0) to disable
SPVR_CUR_OFFSET Currentsensor offset voltage @0A: for ACS758 0.5*ADC_REF_VOLTAGE with some cable loss, calibrate for real values (0) to disable current sensor
SPVR_CUR_RES Currentsensor resolution, adjust after calibration

For the current sensor 2 params are added:
SPVR_CUR_OFFSET 0.0f /* Currentsensor offset voltage @0A */
SPVR_CUR_RES (20.0f/1000.0f) /* Currentsensor resolution in mV/A */
if the SPVR_CUR_OFFSET is 0, the currentsensor measure is disabled. It should be measured direct on the pads when no current is used.
Note: for ACS75x it is usually 0.5*Vref, in this case close to 1.6-1.7V based on 3.3V Vref voltage.

Read more in the forum thread

Transmitter switches: some functions require transmitter switches:

  • Waypoint recording: set a channel for example 5 with momentary switch. Hold >1s to record a waypoint number is displayed in main screen)
  • Waypoint skip: when in mission mode only, the waypoint recording switch is now the waypoint skip switch, it move to the next waypoint in line immediately
  • HoTT Menu: For connivance, a (momentary) switch can be assigned to navigate the menus. Example, set channel 12 (number 11). Press >0.5 sec for main menu and <0.5 for next screen.
This page was created on 17-Mar-14 by kinderkram. Last modified on 10-Oct-14 by kinderkram.