I enabled the ack and tested all possible DTR/RTS configurations with no avail, it usually got until N17 before stopping. I also tried with the smoothieboard firmware but with it only got until N20 before stoping sending the ok.
Here I put the log example:
14:51:27.266 : No start signal detected - forcing start
14:51:27.268 : N1 M11034
14:51:27.269 : Smoothie
14:51:27.269 : ok
14:51:27.269 : N2 M115*36
14:51:27.269 : Smoothie
14:51:27.269 : ok
14:51:27.269 : ok
14:51:27.269 : ok
14:51:27.269 : N3 M10536
14:51:27.270 : ok
14:51:27.270 : ok
14:51:27.270 : N4 M114*35
14:51:27.301 : ok T:28.0 /0.0 @0
14:51:27.301 : N5 M111 S698
14:51:27.301 : ok
14:51:27.301 : ok C: X:0.0000 Y:0.0000 Z:0.0000 E:0.000
14:51:27.301 : ok
14:51:27.301 : N6 T0*60
14:51:27.302 : N7 M2022
14:51:27.302 : ok
14:51:27.302 : ok
14:51:27.302 : N8 M80*19
14:51:27.302 : N9 M10546
14:51:27.302 : ok
14:51:27.302 : ok
14:51:27.304 : Begin file list
14:51:27.304 : system volume information/
14:51:27.304 : config.txt
14:51:27.304 : read_me.txt
14:51:27.304 : spoolholder_v2.gcode
14:51:27.304 : firmware.cur
14:51:27.305 : End file list
14:51:27.305 : ok
14:51:27.305 : ok
14:51:27.305 : ok
14:51:27.307 : ok
14:51:27.311 : ok T:28.0 /0.0 @0
14:51:27.311 : ok
14:51:30.330 : N10 M105*22
14:51:30.334 : ok T:28.0 /0.0 @0
14:51:30.334 : ok
14:51:33.395 : N11 M10523
14:51:33.400 : ok T:28.1 /0.0 @0
14:51:33.400 : ok
14:51:36.454 : N12 M105*20
14:51:36.456 : ok T:27.9 /0.0 @0
14:51:36.456 : ok
14:51:39.517 : N13 M10521
14:51:39.518 : ok T:27.9 /0.0 @0
14:51:39.518 : ok
14:51:42.578 : N14 M105*18
14:51:42.580 : ok T:28.0 /0.0 @0
14:51:42.580 : ok
14:51:45.642 : N15 M10519
14:51:45.644 : ok T:28.1 /0.0 @0
14:51:45.644 : ok
14:51:48.703 : N16 M105*16
14:51:48.705 : ok T:27.9 /0.0 @0
14:51:48.705 : ok
14:51:51.766 : N17 M10517
14:51:51.768 : ok T:28.0 /0.0 @0
14:51:51.768 : ok
14:51:54.829 : N18 M105*30