
Troglotech T815 Crawler Workshop Manual Page 9
T815 CRAWLER- OVERVIEW
T815 Crawler Overview—Electronic Operation Continued
Once the Power Supply is established, the Processor continually communicates
with the Display Unit of the Cable Drum via TTDS signals that are present on
Video+ve. As long as TTDS data is stable and the data contains the
’KEEP_ALIVE_BIT’ (this is set as long as the Display Unit has the correct crawler/
drum software) the processor will hold ‘KEEP AWAKE’ high, which, in turn, holds
‘WAKE’ high. TTDS only works when either the front or rear camera is in
operation, TTDS needs a video signal to operate.
If data is not available the crawler will switch back OFF again. If this cycling
continues, it indicates that the voltage on Video+ve is present but TTDS data is
incorrect or missing. This behaviour will be seen if the software for the Display Unit
(both MAIN and COMMS) has not been updated; pre-T815 software does not
include the ’KEEP_ALIVE_BIT’ bit on TTDS data.
Once TTDS communications are established and the correct data is received the
processor will start communicating with the internal parts via IIC serial bus
The processor has a number of tasks:
Continually send/receive TTDS data
Initialise all IIC devices
Initialise the T812 camera head (if fitted)
Initialise the two motor drives to a safe state
Communicate with the Display Unit via TTDS
Select the video source between front and rear cameras
Switch ON/OFF rear lights
Switch ON/OFF large lighthead
Initialise the accelerometer
Read the accelerometer to get inclination data
Transmit the inclination to Display Unit via TTDS
Switch sonde ON/OFF
Read EEPROM to get calibration data
Get pressure sensor data and calculate true pressure
Get IIC data from current/voltage monitors
Calculate true voltage/current
Transmit voltage/current to Display Unit via TTDS
Calculate crawler orientation for auto-steering
Determine maximum motor speed from voltage data