Mainboard Revisions {{>toc}}

Board design and schematics¶

for Rev2
PDF of the schematics: https://tuxic.nl/laos/hardware/pcb/laos-board-2/output/pdf/laos-board.pdf
PDF of the board: https://tuxic.nl/laos/hardware/pcb/laos-board-2/production/PI_E404084.pdf¶

for Rev3
PDF of the schematics:
PDF of the board:¶

Differences between Rev2 and Rev3¶

Missing Vsensor on endstops¶

In Rev2, the lines marked Vsensor on J29 and J34 and the + side of the opto-couplers are connected with each other, but somehow the connection to the rest of the Vsensor net has gone missing. They should have been connected to Vsensor on J27 and the middle pin of the VCPU/Vsensor/+5V jumper. In Rev3 this problem has been fixed. Vsensor on J27 now has it's own jumper to select the power level.

CAN bus not working¶

In Rev2, there are a few problems with the CAN bus connection.

• U1 pin 8 (Rs) should be connected to GND
• U1 pin 4 (Vref) should be left open
• U1 pin 3 (Vdd) should be connected to 5V (instead of 3V3)
  This has been fixed in Rev3

Swapped label for Direction and Enable¶

In Rev2, the (E)nable and (D)irection pin labels are swapped in the design and on the PCB markings. It does not cause functional problems, as long as you make sure your wiring of external drives is correctly connected. In Rev3, this has been fixed.

Series resistor for analog input¶

In Rev3, an extra resistor (R33) was added between AIN (PIN 3 of J14 and the junction of R10/R12. This allows us to make a voltage divider. Typical value for R33 should be 1K.

Series resistor for analog output¶

In Rev3, an extra resistor (R34) was added between the MBED and AOUT (PIN 2 of J24), in order to limit currents in case of a ground connection of the analog output.

Solder joints for Pololu microstep factor¶

Instead of jumpers, Rev3 has solder joints so it is easier to solder the pins to +V to obtain microstepping. Solder joints: J7, J16, J22 and J31

Moved Ethernet connector
In Rev3, the Ethernet connector has been swapped with the USB to allow easier connection of the MiniUSB connector of the MBED.¶

Added FFC / FPC connector
Rev3 has place for a FFC / FPC connector, as used in some HPC and Chinese Lasers. This connector combines X-Axis stepper and endstops.¶