JRL

TandemZ

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TandemZ

Data bits:

Bit LED
0-bit 0,65 ms high
0,65 ms low
1-bit 1,2 ms high
0,6 ms low

A control signal for the TandemZ consists of the header, 20 data bits and a stop bit.

0,68 ms high
1,20 ms low
2,00 ms high
1,28 ms low

Channel (2 Bits)

Channel Bits (Decimal)
A 00 (0)
B 01 (1)
C 10 (2)

Light (1 Bit)

0-bit for off and 1-bit for on. Even though the light bit is send in every frame, the helicopter saves the last setting, so the LED keeps glowing when there is no more input.

Throttle (4 Bits)

The main rotor has 15 different steps for speed. A 0 is stop, 15 the maximum speed.

Pitch control (3 Bits)

The pitch can be controlled by 6 steps. One center step, three forward and two backwards steps.

The remote control changes the yaw trim by 4 steps, when one of the backward steps are used.

Pitch control Bits (Dezimal)
backwards 2 000 (0)
backwards 1 001 (1)
center 010 (2)
forward 1 011 (3)
forward 2 100 (4)
forward 3 101 (5)

Pitch trim (5 Bits)

The pitch can be trimmed by 32 steps, where 00000 (0) is maximum forward and 11111 (31) is maximum backwards.

Yaw (5 Bits)

The yaw uses 5 bits, too. 00000 (0) is totally left and 11111 (31) totally right.

The remote control doesn’t make use of every possible step, it’s missing steps 3-5, 19-22, 27-29. That leaves 22 steps for yaw control. The helicopter does not accept the missing steps as valid input (AVR firmware remaps invalid input to the closest valid step).

The yaw trim poti on the remote control also changes yaw control, there is no seperate yaw trimming.

Check sum (3 Bits)

The last 3 bits are used for the check sum. Its calculated over the 20 data bits.

The check sum can be interpreted as 3 bit number. Starting with 000 for every 1-bit either 001 (1), 010 (2) or 100 (4) is added depending on the bit’s position in the data stream.

Function Channel Light Throttle Pitch control Pitch trim Yaw trim
Addition to check sum 010 (2) 001 (1) 100 (4) 100 (4) 100 (4) 010 (2) 001 (1) 100 (4) 010 (2) 001 (1) 010 (2) 001 (1) 100 (4) 010 (2) 001 (1) 010 (2) 001 (1) 100 (4) 010 (2) 001 (1)

Stop bit (1 Bit)

Single 0-bit with the same encoding as data bits.

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