The parallel reconstruction of the command impulses starting from the commands received on USB is carried out by an ATmega2560 microcontroller interfaced to a USB / TTL converter in the microcontroller we loaded the grbl firmware. creating something that is actually an interpreter subsystem of the commands sent by the CNC control software: a card that connects on one side to the USB and on the other, through a DB-25 connector, to the parallel of the 3-axis controller card of the CNC and which interprets the commands received, extracts them from the serial strings arriving on the USB and reconstructs the commands on a parallel connection, reassigning them the right timings and temporal consistency with the impulses of all the command lines. This procedure involves, due to latency, problems of synchronization between pulses (because Mach 3 controls the motors and their lines as drivers line by line) and time coherence, therefore it is not advisable to use a USB / parallel adapter. Who then should extract them and rearrange them in parallel form. If you tried to communicate via USB with a converter, first of all a virtual LPT corresponding to the USB would be opened with the appropriate drivers, then the data would be serialized and then transferred along the USB to the USB / parallel converter, Mach 3 executes the G-code and emits specific pulses for the motors, one per pin of the parallel, synchronized and time coherent. To understand the usefulness of the interface it must be said that in common CNCs on LPT port the command is given by the machining software (for example Mach 3) which, starting from the file in G-code language, sends impulses directly to the parallel lines to advance the respective axes by a certain number of steps / mm. It allows to use, through the USB port of the PC, the traditional three-axis control cards of a CNC that work on parallel port.Īttention: The USB cable and the cable for connection to the RESET connector are not included in the package, therefore if necessary they must be purchased separately (see the related ones for the product codes).īuy all the accessories in our shop on EBAY | MECTRONICA STORE Based on the ATmega2560 with GRBL firmware installed, this board has a USB / TTL converter, DB25 connector, USB port for powering and connecting to the PC, relay output for connecting an electrospindle.
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