docs: sensors

philiplinden · Dec 19, 2024 · 08c96b1 · 08c96b1
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diff --git a/docs/SUMMARY.md b/docs/SUMMARY.md
@@ -3,8 +3,8 @@
 # Home
 
 - [introduction](introduction.md)
-- [structure](design/structure.md)
-- [sensors](design/sensors.md)
+- [system architecture](design/system-architecture.md)
+- [hardware](design/hardware.md)
 
 ---
 

diff --git a/docs/captains-log.md b/docs/captains-log.md
@@ -1,5 +1,50 @@
 # captain's log
 
+## 2024-12-18
+
+There's a rust project that claims to support raspberry pi and stm32 boards,
+[embassy.dev](https://docs.embassy.dev/embassy-stm32/git/stm32f411ve/index.html)
+that looks interesting. I'm not sure how it differs from the `cortex-m` crates
+I've been using, but it might be worth checking out.
+
+- It looks like Embassy can auto-generate the `memory.x` file for the board.
+- The docs are really good and filtered by the specific chipset.
+- Doesn't look like it supports the MSP432.
+
+I also did some shopping for parts, but I didn't order anything yet. Here are
+the parts I'm considering:
+
+- [RFM96W LoRa Transceiver (915 MHz)](https://www.sparkfun.com/products/12775).
+  This also comes in a 433 MHz version, but as far as I can tell it's a region
+  lock thing---The Americas use 915 Mhz for the license-free ISM band. The 915
+  MHz version has an operating power of up to 100 mW and 300 kbps, which should
+  be enough for me.
+- [NEO-M9N GPS](https://www.sparkfun.com/products/18378). According to
+  the datasheet it should work up to 80 km. This is the newest version of this
+  chip but I think modules as old as NEO-M6 would work.
+- [BME280 Atmospheric Sensor](https://www.sparkfun.com/products/15440). The
+  myth, the legend, the classic pressure, humidity, and temperature sensor.
+
+Some other parts that are overkill but would be nice to have:
+
+- [Qwiic MicroPressure Sensor](https://www.sparkfun.com/products/16476). This is
+  a barometer that has a calibrated sensing range of 60mbar to 2.5bar. I think
+  it would be useful to have a sensitive barometer for higher altitudes where a
+  more general purpose barometer might not be sensitive enough.
+- [OpenLog Artemis](https://www.sparkfun.com/products/16832). This is a
+  data logger board with a built-in IMU, voltage loggers, some high-rate
+  sampling for a few channels or ~250Hz logging in general. It automatically
+  detects, configures, and logs Qwiic boards, including all the sensors I'd want
+  to use for this project.
+- [Waveshare Environment Sensor HAT](https://www.waveshare.com/environment-sensor-hat.htm).
+  This is basically a glorified BME280 carrier board with a few other sensors
+  like UV, air quality, and convenient Raspberry Pi GPIO headers.
+- [BerryGPS-IMU](https://ozzmaker.com/product/berrygps-imu/). A fancy all-in-one
+  motion sensor designed to fit perfectly with the Raspberry Pi Pico. Fancy.
+  Overkill. Cool, though. It has a GPS, 10DOF IMU, barometric altimeter,
+  magnetometer, and temperature sensor. This board uses the CAM-M8 GPS module
+  from u-blox, which dies at 50 km altitude.
+
 ## 2024-12-17
 
 Ahab is a fitting name for this project. It is a high altitude balloon. It is

diff --git a/docs/design/hardware.md b/docs/design/hardware.md
@@ -0,0 +1,49 @@
+# Hardware
+
+## Observables
+
+Here is a (non-exhaustive) list of sensors and the observables they can could
+provide.
+
+| Sensor                | Observables                                                                 |
+| --------------------- | --------------------------------------------------------------------------- |
+| Clock                 | Time                                                                        |
+| GPS                   | Position, velocity                                                          |
+| IMU                   | Orientation, Velocity, Angular velocity, Acceleration, Angular acceleration |
+| Barometer             | Air pressure                                                                |
+| Barometric Altitmeter | Air pressure, altitude                                                      |
+| Thermometer           | Air temperature                                                             |
+| Hygrometer            | Air humidity                                                                |
+
+And maybe some other telemetry that would be derived from the above sensors.
+
+| Source                                                 | Observable                 |
+| ------------------------------------------------------ | -------------------------- |
+| Air temperature, humidity, pressure                    | Air density                |
+| Ballistic trajectory vs observed velocity and position | Wind speed, wind direction |
+| Dead reckoning from accelerations                      | Position, velocity         |
+
+## Parts
+
+- [RFM96W LoRa Transceiver (915 MHz)](https://www.sparkfun.com/products/12775).
+  This also comes in a 433 MHz version, but as far as I can tell it's a region
+  lock thing---The Americas use 915 Mhz for the license-free ISM band. The 915
+  MHz version has an operating power of up to 100 mW and 300 kbps, which should
+  be enough for me.
+- [NEO-M9N GPS](https://www.sparkfun.com/products/18378). According to
+  the datasheet it should work up to 80 km. This is the newest version of this
+  chip but I think modules as old as NEO-M6 would work.
+- [BME280 Atmospheric Sensor](https://www.sparkfun.com/products/15440). The
+  myth, the legend, the classic pressure, humidity, and temperature sensor.
+
+Some other parts that are overkill but would be nice to have:
+
+- [Qwiic MicroPressure Sensor](https://www.sparkfun.com/products/16476). This is
+  a barometer that has a calibrated sensing range of 60mbar to 2.5bar. I think
+  it would be useful to have a sensitive barometer for higher altitudes where a
+  more general purpose barometer might not be sensitive enough.
+- [OpenLog Artemis](https://www.sparkfun.com/products/16832). This is a
+  data logger board with a built-in IMU, voltage loggers, some high-rate
+  sampling for a few channels or ~250Hz logging in general. It automatically
+  detects, configures, and logs Qwiic boards, including all the sensors I'd want
+  to use for this project.
diff --git a/docs/design/sensors.md b/docs/design/sensors.md
diff --git a/docs/design/structure.md → docs/design/system-architecture.md b/docs/design/structure.md → docs/design/system-architecture.md
@@ -1,4 +1,4 @@
-# Structure
+# System Architecture
 
 In the [introduction](introduction.md) I mentioned that Rust allows us to
 _theoretically_ write everything in Rust. This is a sketch of how I think the
@@ -27,7 +27,7 @@ Let's see if we can break down those systems into "blocks" of systems.
   a self-contained system. There are known physics rules and the state of those
   objects continues to evolve by those rules without any external input from an
   agent.
-- **[Sensors](sensors.md)** - Physically, sensors are self-contained systems.
+- **Sensors** - Physically, sensors are self-contained systems.
   They observe data about the world and convert it into some format, then ship
   it elsewhere. The source of the observation and the destination of the data
   can be abstracted or simulated or whatever. Sensors are often simple hardware