# Marlin - slowing down print speed

I'm currently using Marlin firmware (1.1.0-RC7 - 31 July 2016) and would like to experiment with print speed.

In the file Marlin_main.cpp I see in the process_next_command() function, there is a variable called current_command which (supposedly) holds the G-Code values for travel distance and feedrate(speed).

I'm expecting the actual command for travelling to look something like this:

G1 X50 Y25.3 E22.4 F1500


but I'm getting tied up figuring out exactly where it is. I'm assuming if I can change F1500 to F200, I can effectively slow down the print speed.

I'm aware of line 753 in the configuration.h file:

#define DEFAULT_MAX_FEEDRATE {300, 300, 5, 25}  // (mm/sec)


I'm not interested in setting a fixed slow feedrate but would rather change individual G-Code commands. Can someone tell me where I can find the actual G-Code command to edit it?

The commands are processed in the process_commands of Marlin_main.cpp. Upon reading a G1 command, it calls get_coordinates to parse the X/Y/Z/feedrate values from the command. Next, the prepare_move function is called, which applies the necessary transformations (clamping to endstops, and the reverse kinematics if you have a delta) before calling plan_buffer_line (which is in planner.cpp) which does some more preprocessing and computes a "block" which is pushed onto the buffer. Next, planner_recalculate is called, which iterates over the blocks to find feasible acceleration patterns for them. Finally, an interrupt (in stepper.cpp, ISR(TIMER1_COMPA_vect)) periodically reads blocks from the buffer and actually sends the signals to the steppers.