Based on the ATmega2560 with GRBL firmware installed, this card has USB / TTL converter, DB25 connector, USB port for power supply and PC connection, Relay output for connecting an electric spindle. It allows you to use the traditional three-axis control boards of a CNC that work parallel to the PC through the PC's USB port.

Caution: The USB cable and headset for connection to the RESET connector are not included in the package, so if necessary they must be purchased separately.

To understand the utility of the interface, it is to be said that in the common CNC port on LPT the command is given by the machining software (for example Mach 3) starting from the G-code language file sends directly to the parallel pulse lines to advance The respective axes of a number of steps / mm. Mach 3 performs G-code file and control the parallel port pins to move the motors.

If you were trying to communicate via USB with a converter, it would first be possible to open a virtual LPT corresponding to the USB with the case drivers, then the data would be serialized and then transferred along the USB to the USB / parallel converter,
Which should then extract them and rearrange them in parallel form. This process involves, due to latency, impulse synchronization problems (because Mach 3 drives line by line to motors and their driver lines) and time consistency, so it is advisable to use a USB / parallel adapter. We've been circumventing the problem Realizing something that is actually a commanding subsystem of commands sent by the CNC control software: a board that connects to one side to the USB and, by means of a DB-25 connector, to the parallel of the 3 axis controller board CNC and interprets received commands, extracts them from incoming serial strings on the USB, and rebuilds commands on a parallel connection by reassigning them with the right timings and time consistency with the pulses of all command lines.

The parallel control of the control pulses from commands received on USB is carried out by an ATmega2560 microcontroller interfaced with a USB / TTL converter; In the microcontroller we loaded the grbl firmware. So our card receives G-Code coordinates from USB and locally generates impulses on its parallel, which drives the original printer controller.
For how the firmware we choose, we can not use Mach 3, but software that goes on USB but something like GRBL sender, which sends coordinates in the format that our card reads.