you just have to mix X and Y on the joystick…
Here is the link to my issues on the subject.
Here is the picaxe code to go from a (2) up-down joysticks to one up-down / R-L joystick when controlling 2 motors (one on each side)
This comes from robologist as a comment in the post above:
Take that values from the joystick as it sits, up-down axis called Y with values given from 75 bottom to 225 top, right-left values called axis X with 225 left, 75 right.
Y
225
X 225 <> 75 Joystick
75
PWM values for left and right wheels can then be calculated from formulas :
L_PWM = (Y - X) + 150
R_PWM = (Y+ X) - 150
Evaluation of calculated output :
Direction (Y,X) :
Full Fwd (225,150): L_PWM = (225 - 150) + 150 = 225, R_PWM = (225 + 150) - 150 = 225
Full Rev (75,150) : L_PWM = (75 - 150) + 150 = 75, R_PWM = (75 + 150) - 150 = 75
spin CW (150,225): L_PWM = (150 - 225) + 150 = 75, R_PWM = (150 + 225) - 150 = 225
spin CCW (150,75): L_PWM = (150 - 75) + 150 = 225, R_PWM = (150 + 75) - 150 = 75
curve forward left (205,205): L_PWM = (205 - 205) + 150 = 150, R_PWM = (205 + 205) - 150 = 260, out of range
curve forward right (205,95): L_PWM = (205 - 95) + 150 = 260 out of range, R_PWM = (205 + 95) - 150 = 150
curve back left (95,205): L_PWM = (95 - 205) + 150 = 40 out of range, R_PWM = (95 + 205) - 150 = 150
curve back right (95,95): L_PWM = (95 - 95) + 150 = 150, R_PWM = (95 + 95) - 150 = 40 out of range
Might be needed to limit max and min range values for PWM output.