Electronics assembling notes

Schematic for v4: Link

Recommended PCB assembling sequence:

1. Install 3.3V linear voltage regulator, MCU, programming and UART header, LED, quartz. Load "not_sсanning_firmware" to MCU.
   If the firmware is running, LED must blink and you can read parameters from MCU by "LidarTestingUtility".
2. Install TDC, all components around it, including its quartz (and its passive components). Enable "Auto Request Batch" in utility. There must be pulses at "LASER_PULSE" net (~1 ms period, 1us width, 3.3V amplitude).
3. Install laser DC-DC components, laser MOSFET driver. Check "Vlaser" - it must change by manual commands from utility. Check that pulses presents at the MOSFET driver output (pins 2,3).
4. Install MOSFET, Laser diode, diode D7, and other lasers components. Do not use leaded resistor for R19! Check that laser is working by camera (notice that not all cameras can "see" IR light). Do not look to the laser!! Check laser current pulses by connecting J2 to the oscilloscope. Current must change with changing "Vlaser". Examples: Link
5. Install lasers comparator components. Check pulses at the comparator output.
6. Install APD DC-DC components (Q1 and others), but do not install TIA (DA3) at this step!
   Notice that L5 inductor must we "Wire Wound" type, not multilayer!
   Check "APD_V" - it must be changing by manual commands from utility. Confirm that "APD Volt" value displayed in utility is the same as "APD_V" (measured by voltmeter).
   If you can get >100V, you can set target APD voltage using "APD Targ. Volt" - see Link
7. Install protection diode D6, C1, L1. TIA is very sensitive to static electricity (ESD)!
8. Install TIA (DA3) and other components.
9. Install APD. Check pulses at J1 - they should appear if there is some object get close to laser and APD. Don't forget that APD gain is depending on "APD_V".
10. Install APD comparator components. Check pulses at the comparator output.
11. Install BLDC motor driver. Check that motor is working. You can try to set PWM value manually at the utility ("Motor Settings" -> "Motor Manual PWM" -> "Set") Right motor direction is CCW when you looking to the Lidar from the top.