missing i2c communication protocol description about tgy HOT 2 CLOSED

Hello! The protocol is pretty simple, and is implemented to be compatible with MikroKopter brushless ESCs ("BL-Ctrl") version 1 and 2. You can see host-side implementation here: http://svn.mikrokopter.de/filedetails.php?repname=FlightCtrl&path=%2Ftags%2FV0.74d%2Ftwimaster.c

Basically, the input follows the same path as PWM and UART inputs. You need to arm the ESC by sending 0 at power-up at a rate high enough to satisfy the pulse timeout (at least ~20Hz). Then, the simplest control is simply a byte from 0 (off) to 247 (full power). Search for "evaluate_rc_i2c:" to see the bottom half of the i2c interrupt, where the input is processed to form a PWM duty. The protocol version 2 adds a few more bits, three usable, in the second byte, giving you a resolution of about 11 bits, assuming there is enough bandwidth to do so.

Finally, there is some more advanced configuration structure stuff that allows various things to be read and set. The only thing implemented at the moment is reversing the direction of rotation (through MikroKopter Tool).

from tgy.

Thank you for the links!
With the help of those, I'm able to use the i2c interface to drive motors in one direction. However, I don't quite understand how to send in the second byte to reverse direction..
Currently, I'm using this function from i2c-dev.h
static inline __s32 i2c_smbus_write_byte(int file, __u8 value)

My control loop is structured roughly as follows

while(1) {
    i2c_smbus_write_byte(i2c_dev_fd, cur_speed);
    usleep(1000);
}

Should this 'second byte' just be another i2c_smbus_write_byte() call inside the loop?

from tgy.