Update readme

README.md

@@ -14,29 +14,38 @@ Premium SmartKnob experience. Under active development.
 ### SmartKnob Handheld
 An exploration of a small handheld form-factor. Under active development.
 
+<a href="doc/img/PXL_20220212_013249074.jpg"><img src="doc/img/PXL_20220212_013249074.jpg" width="200" /></a>
+
 ### SmartKnob Mini
 Planned for the future.
 
 ## Component Info
 
 ### Magnetic encoders
-#### TLV493 (Infineon)
-A decent choice, and easy to prototype with using [Adafruit's QWIIC breakout board](https://www.adafruit.com/product/4366).
+#### TLV493D (Infineon)
+A mediocre choice. Easy to prototype with using [Adafruit's QWIIC breakout board](https://www.adafruit.com/product/4366).
 
 In my testing, it is a little noisy, requiring filtering/smoothing that can slow responsiveness, hurting control loop stability. Or, with less filtering, the noise
 can easily be "amplified" by the derivative component in the PID motor torque controller, causing audible (and tactile) humming/buzzing.
 
-There is also apparently a somewhat common issue with the internal ADC locking up, requiring a device reset (see datasheet section 5.6). From a random sample of 4 Adafruit breakout boards, 2 of them (50%) appear to be extremely prone to this - locking up within a minute or so of use! Further testing is planned, but this may be a deal-breaker.
+There is also apparently a known silicon issue that causes the internal ADC to sometimes completely lock up, requiring a full reset and re-configuration. See section
+5.6 in the [User Manual](https://www.infineon.com/dgdl/Infineon-TLV493D-A1B6_3DMagnetic-UM-v01_03-EN.pdf?fileId=5546d46261d5e6820161e75721903ddd)
+
+    In the Master Controlled Mode (MCM) or the Fast Mode (FM) the ADC conversion may hang up. A hang up can
+    be detected by:
+     - Frame Counter (FRM) counter stucks and does not increment anymore.
+
+In my experience testing 4 different Adafruit breakout boards, 2 of them (50%) regularly exhibit this lockup behavior within a minute or two of use.
 
 As of 2022-02-08, there is limited availability of this IC.
 
 [Datasheet](https://www.mouser.com/datasheet/2/196/Infineon_TLV493D_A1B6_DataSheet_v01_10_EN-1227967.pdf)
 
 #### MT6701 (MagnTek)
-Very promising based on the datasheet and initial prototyping.
+Very promising based on the datasheet and initial tests. Seems to be less noisy than TLV493D, and more responsive (control loop is more stable) using SSI.
 
- - Haven't testing in a full control loop yet, but data looks good and relatively noise-free.
- - Lots of IO options - SPI, I2C, and ABZ - should offer good response latency.
+ - Lots of IO options - SSI, I2C, and ABZ - should offer good response latency
+ - SSI include CRC to validate data
  - No power-down or low-power options - may not be ideal for battery-powered devices
  - Not available from US distributors (Mouser, Digi-Key)
 
@@ -58,11 +67,43 @@ Highlights:
  [Product page](https://www.trinamic.com/products/integrated-circuits/details/tmc6300-la/)
 
 ### Motors
-TODO
+#### 32mm Rotor, Hollow Shaft, Diametric magnet
+<a href="doc/img/motors/PXL_20220121_221746595.jpg"><img src="doc/img/motors/PXL_20220121_221746595.jpg" width="200" /></a>
+<a href="doc/img/motors/PXL_20220121_221738745.jpg"><img src="doc/img/motors/PXL_20220121_221738745.jpg" width="200" /></a>
+
+
+- 32mm rotor
+- 15mm overall height (including magnet), 12.75mm height w/o magnet, 9mm rotor height
+- low/zero cogging - excellent for completely smooth input
+- 5.9mm hollow shaft
+- built-in diametric magnet for encoder
+- Proven option
+
+This is overall the easiest motor to get started with. Low cogging and a built-in diametric magnet are great!
+
+[AliExpress](https://www.aliexpress.com/item/1005001384349991.html)
+
+#### ~17mm Rotor
+<a href="doc/img/motors/PXL_20220121_220530808.jpg"><img src="doc/img/motors/PXL_20220121_220530808.jpg" width="200" /></a>
+<a href="doc/img/motors/PXL_20220121_220546761.jpg"><img src="doc/img/motors/PXL_20220121_220546761.jpg" width="200" /></a>
+
+- Not tested yet
+- Stepped 17.3mm and 16.3mm diameter rotor
+- 11.2mm total height, 8.6mm rotor height
+- moderate cogging - not ideal for completely smooth input
+- Rotor has threaded hole on the side that should be usable for keying a cap
+- Very little shaft accessible on bottom - may be tricky to mount a diametric magnet to it. Maybe could replace screw with something else?
+
+[AliExpress](https://www.aliexpress.com/item/1005003240145615.html)
 
 # Firmware
 TODO
 
+# Acknowledgements
+This project was greatly inspired by Jesse Schoch's video "[haptic textures and virtual detents](https://www.youtube.com/watch?v=1gPQfDkX3BU)" and the
+corresponding [discussion in the SimpleFOC community](https://community.simplefoc.com/t/haptic-textures/301).
+
+
 # License
 
 This project is licensed under Apache v2 (see [LICENSE.txt](LICENSE.txt)).