Hello.
If solder buffers for input can be used with H-bridge
for driving dc brushed servos with incremental encoder feedback ?
( pwm output / step-dir-quadrature output / encoder input / gpio )
What input buffer chips are needed and how to solder ? what modifications needed ?
example for 5A-75E v8 ?
(here does not have example for that version
litex-cnc.readthedocs.io/en/latest/examples/index.html
)
For changing the buffers you would need to get som
74LVC245
buffers. The letters LVC are important here, because these buffers are 5V tolerant, whilst Vcc can be 3.3 Volts.
For removing the old buffers I use a small pliers and cut all the legs. After that it is easy to remove the remainder of the leg from the solder pads one by one with some flux. This method prevents ripping pads of from the board.
Now you have to cut the traces to pin 1 and 20. Pin1 is for direction and normally connected to 5 V. Pin 20 is Vcc and is also connected to the 5 V rail. Check and double check whether the pads are disconnected with a multimeter.
Now you can solder the new buffer in place. Connect pin 1 to GND, for example make a jumper to pin 10 of the adjacent buffer. Pin 20 has to be connected to 3.3 volt supply, for example from the JTAG header. Now the conversion is done.
Now for the first part of the question: the H-bridge. I mentioned this as a way to drive stepper motors. For a DC motor you can try it, but maybe the loop from encoder - > fpga - > linuxcnc - > fpga - > motor is too slow. The loop take 1 ms, which is 1 kHz. Please try, although you have to whip this together in the Hal.
