Commit VL53L1x project (#114)

projects/Thomas_VL53L1x_pwm/README.md

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+---
+name: "Thomas Anderson"
+slack_handle: "Thomas Anderson"
+github_handle: "tandej"
+project: "VL53L1x_pwm"
+---
+
+# VL53L1x_pwm
+## Summary
+The VL53L1x and company are great sensors with a lot of utility, but the I2C protocol and required device drivers can be quite clumsy in certain applications. This board uses a STM32 microcontroller in a very small form factor to adapt from that protocol to a standard duty-cycle output at the logic level that it is powered with.
+
+## Fabrication
+Gerber files, BOM and component placement files can be found in /VL53L1x_pwm/JLC_output. To ensure that those files are up-to-date with the source, run:
+```
+$ pip3 install kikit
+$ chmod +x VL53L1x_pwm/KiKitJLCGen.sh
+$ VL53L1x_pwm/KiKitJLCGen.sh
+```
+The shell script can trivially be converted to a batchfile for Windows users.
+
+JLC's SMT assembly GUI doesn't automatically assign a part for a few parts. I used NX3225SA-16MHZ-EXS00A-CS10477 for crystal Y1 and X1270WV-2x05B-6TV01 for connector J1. Otherwise, generic passive components like resistors and capacitors generally have no requirements other than their footprint and value (capacitor C1 needs to be rated for 16v).
+
+## Plan
+![cart](cart.png)
+
+The boards are quite small and only 2-layer, so the cost comes to only $4 for all 5 boards. The assembly takes up most of the budget, coming to $75.86. Shipping wasn't shown, but I expect it to cost <$20 given the size of the boards and prior experience with JLC.
+
+The board is pretty much done after I recieve it, so all I have to do is write the firmware for the device. That should be quite easy with STM32duino and an STLink for SWD programming.
+
+## Design
+![schematic](VL53L1x_pwm.png)
+
+I started this project planning to use the VL53C4x sensor for its slightly better performance. I also planned to use a small-form-factor STM32 for the ease of programming that it offered and prior personal experience with STM32F04 and F09 ARM M0 processors. 
+
+At this point I ran into a conflict between a small, inexpensive microcontroller and VL53C4x, as I found that the (required) STM device drivers used upwards of 50 kB of flash memory, which was well over total internal flash budget. If I had more experience with embedded development, I probably could have made this work with execute-in-place on a SPI external flash chip, but I didn't really think that was feasible.
+
+Pivoting to the VL53L1x, my job was a lot easier as the drivers only use \~2.3 kB of flash. The VL53L1x specifically operates at 1.6v\~2.8v logic level, which drove my choice specifically to the STM32L011k for its 1.8v operating level. Doing an I2C shift would be possible, but would introduce a lot of potential problems with high-speed communications. Just shifting SWD and the PWM output would be a lot easier.
+
+A last-minute addition was the INT (interrupt) output pin, as I realized that the sensor update rates weren't quite as good as I thought, and so downstream devices could easily find a notification of new updates useful.
+
+---
+
+[X] I am a current high school, middle school, or home schooled student.
+
+[X] I have filled out the [verification form](https://airtable.com/shrbcDANe6ug6gj0p)
+
+[X] I have joined the [`#onboard`](https://hackclub.slack.com/archives/C056AMWSFKJ) channel on Slack
+
+[X] I made this board from scratch, even if I followed a tutorial
+
+[X] I have followed [DIRECTIONS.md](https://github.com/hackclub/OnBoard/directions.md)
+
+[X] Created a folder under `onboard/projects`
+
+[X] Filled out `TEMPLATE.md`
+
+[X] Uploaded Gerber and design files
+
+[X] Uploaded screen shot of PCB passing vendor inspection
+
+[X] I am ordering the smallest batch size (ie. JLCPCB's smallest order is for 5 boards)
+
+[X] If outside the US I've checked that I can afford the customs charges in my country (which isn't covered by the grant)

projects/Thomas_VL53L1x_pwm/VL53L1x_pwm/JLC_output/bom.csv

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+Comment,Designator,Footprint,LCSC
+1 uF,C1,Capacitor_SMD:C_0402_1005Metric,
+10 pF,"C2,C9",Capacitor_SMD:C_0402_1005Metric,
+0.1 uF,"C3,C4,C5,C11",Capacitor_SMD:C_0402_1005Metric,
+4.7 uF,"C6,C8,C10",Capacitor_SMD:C_0603_1608Metric,
+10 nF,C7,Capacitor_SMD:C_0402_1005Metric,
+D_Schottky,D1,Diode_SMD:D_SOD-323F,
+Conn_02x05_Odd_Even,J1,Connector_PinHeader_1.27mm:PinHeader_2x05_P1.27mm_Vertical,
+BSS138,"Q1,Q2,Q3,Q4",Package_TO_SOT_SMD:SOT-23,
+10k,"R1,R2,R3,R4",Resistor_SMD:R_0402_1005Metric,
+LP2985-1.8,U1,Package_TO_SOT_SMD:SOT-23-5,
+STM32L011D4Px,U2,Package_SO:TSSOP-14_4.4x5mm_P0.65mm,
+VL53L1CXV0FY1,U3,Sensor_Distance:ST_VL53L1x,
+16 MHz 9 pF,Y1,Crystal:Crystal_SMD_3225-4Pin_3.2x2.5mm,

projects/Thomas_VL53L1x_pwm/VL53L1x_pwm/JLC_output/gerber/VL53L1x_pwm-CmtUser.gbr

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+G04 #@! TF.CreationDate,2023-06-19T15:46:02-07:00*
+G04 #@! TF.ProjectId,VL53L1x_pwm,564c3533-4c31-4785-9f70-776d2e6b6963,rev?*
+G04 #@! TF.SameCoordinates,Original*
+G04 #@! TF.FileFunction,Other,Comment*
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