4th axis on RAMBO using motor extensions

Mostly Printed CNC - MPCNC Hardware Development
15

Gotcha, thank you both for explaining. In retrospect this makes sense.

  1. When I compile the firmware in VS with platformio (without making any changes) I get some warnings just like expressed in this post. I guess it’s not a big deal but why aren’t those resolved in the final v1 firmware? Or is it my fault?

  2. Do I want my pins for the motor extension to be defined as for the “I” or “A” motor in the pins file? I find it a little confusing that they the non-X/Y/Z axies have two names. I think “I” is the name I should use and “A” is just the name it is mapped to for gcode commands but correct me if I am wrong.

  3. Random question but why are the motor drivers defined in marlin as a4988 when it says on the schematic that they are a4982? Is a4982 not an option? I see that a4982 only have two micro-stepping pins so they are at least slightly different from each other.

Here is everything I added/changed with the firmware- all in the config, advanced config, or pins files. I just followed the chain of errors, which was surprisingly easy to do :slight_smile: It seems to have built so I hope to try and flash it at the end of the week!
A lot of the errors had to do with homing which is a shame because I never plan to using homing on a rotary axis. It looks like it may be possible to not have to set up homing by just removing some of the sanity checks, but that sounds a bit risky. I reused the X_MIN_PIN number for the I_MIN_PIN, is this a bad idea?

#define I_STEP_PIN 22
#define I_DIR_PIN 32
#define I_ENABLE_PIN 44

uncomment #define I_DRIVER_TYPE A4988
comment #define AXIS4_ROTATES
uncomment #define I_MIN_POS 0
uncomment #define I_MAX_POS 50
uncomment #define I_HOME_DIR -1
uncomment #define I_ENABLE_ON 0
uncomment #define DISABLE_I false
uncomment #define INVERT_I_DIR false
uncomment #define USE_IMIN_PLUG

add #define I_MIN_PIN 12

add false #define AXIS_RELATIVE_MODES { false,
add 5 #define HOMING_BUMP_MM { 5,
add 2 #define HOMING_BUMP_DIVISOR { 2
add a good number #define DEFAULT_AXIS_STEPS_PER_UNIT { 100,
add 25 #define DEFAULT_MAX_FEEDRATE { 50,
add 80 #define DEFAULT_MAX_ACCELERATION
add (3560) #define HOMING_FEEDRATE_MM_M { (3560)
add 50860 #define MANUAL_FEEDRATE { 50*60,

You have both mentioned PWM pins in your posts, do you know that nema/a4988 need PWM pins? I have not been able to find anywhere that this is the case. Maybe some of the fancier drivers need PWM pins?
Additionally the schematic has pwm in green (or just green labels) on some of the pins. However, none of the existing motor drivers (a4982) seem to be using them.

Thanks again for any input!