The following formulas are used to calculate possible range of feed speed:
minimum possible feed speed = encoder_ lines / (motor_steps_Z * microstep_Z * 255 / screw_pitch_Z)
For example:
1800 / (200 * 4 * 255 / 1.5) = 1800/136000 = 0.013
round up to 0.01 mm, so the the minimum possible feed rate in this example is 0.02 mm / rev.
Just in case - let's check the maximum possible feed rate = encoder_ lines / (motor_X steps * microstep_X / screw_pitch_X)
For example:
1800 / (200 * 4 / 1.0) = 1800/800 = 2.25 mm / rev
So in this example we would configure useful range of feeds 0.02 / 0.03 - 0.20 / 0.25.
For AM882 driver owners, make corrections in lines 70 and 75:
#define Motor_Z_Enable() do {PORTL |= (1<<4); _delay_ms(80);} while(0)
#define Motor_X_Enable() do {PORTL |= (1<<3); _delay_ms(80);} while(0)
[and then he lists some features omitted from the 7a_LITE version - let me know if you need that]