LAOS Laser

h1. Mainboard Revisions

h2. Differences between Rev2 and Rev3

h3. 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.

h3. 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

h3. 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.

h3. 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. 

h3. 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. 

h3. 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

h3. 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.

h3. 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.