I've been trying to use my prusa i3 printer with Marlin to move around a laser, switching it on and off using the command: M42 D11 SXX. The laser has TTL communication and should be able to support a pwm input. My board is an MKS Base (a single-board ramps 1.4 setup) and D11 is a pwm pin that is exposed to control servos. The issue is that although I'm able to switch the pin between output between 0 and 5V using M42 D11 S0 and M42 D11 S255, respectively, I can't get any values in between. Anything from S0 to S128 yields 0V and S128 to S255 gives me 5V. What's going on here? Why is D11 acting like a plain digital output? I've tried the above on pins D12, A11, A12, and D2 (For D2 I disabled a max endstop, it's pullup resistor, and removed it from the sensitive pins list). I even edited out the "digitalwrite" line of M42 in Marlin's main.cpp. Always the same behavior. Is this a bug with M42? Is pwm disabled on my board for some reason? Am I crazy? Thanks in advance. https://reprap.org/forum/read.php?147,651203,651203#msg-651203 Fri, 11 Sep 2026 13:18:40 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?147,651203,651563#msg-651563 https://reprap.org/forum/read.php?147,651203,651563#msg-651563 I would not use D10.]]> Wurstnase Firmware - experimental, borrowed, and future Tue, 12 Apr 2016 12:40:44 -0400 https://reprap.org/forum/read.php?147,651203,651558#msg-651558 https://reprap.org/forum/read.php?147,651203,651558#msg-651558 heyisaacsback Firmware - experimental, borrowed, and future Tue, 12 Apr 2016 12:16:52 -0400 https://reprap.org/forum/read.php?147,651203,651447#msg-651447 https://reprap.org/forum/read.php?147,651203,651447#msg-651447
Edit: Yes, it's used for the stepper interrupt.]]> Wurstnase Firmware - experimental, borrowed, and future Tue, 12 Apr 2016 07:31:25 -0400 https://reprap.org/forum/read.php?147,651203,651203#msg-651203 https://reprap.org/forum/read.php?147,651203,651203#msg-651203
The issue is that although I'm able to switch the pin between output between 0 and 5V using M42 D11 S0 and M42 D11 S255, respectively, I can't get any values in between. Anything from S0 to S128 yields 0V and S128 to S255 gives me 5V.

What's going on here? Why is D11 acting like a plain digital output? I've tried the above on pins D12, A11, A12, and D2 (For D2 I disabled a max endstop, it's pullup resistor, and removed it from the sensitive pins list). I even edited out the "digitalwrite" line of M42 in Marlin's main.cpp. Always the same behavior. Is this a bug with M42? Is pwm disabled on my board for some reason? Am I crazy?

Thanks in advance.]]> heyisaacsback Firmware - experimental, borrowed, and future Mon, 11 Apr 2016 15:12:07 -0400