Better structure definitions

README.md

@@ -2,43 +2,61 @@
 
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-[Pixhawk](http://pixhawk.org) is an independent open-hardware project that aims to provide the standard for readily-available, hiqh-quality and low-cost autopilot hardware designs for the academic, hobby and developer communities. Pixhawk supports multiple flight stacks: PX4 ® and ArduPilot ®.
+[Pixhawk](http://pixhawk.org) is an independent open-hardware project that aims to provide "the gold standard" for readily-available, hiqh-quality and low-cost autopilot hardware designs for the academic, hobby and developer communities.
+Pixhawk supports multiple flight stacks: PX4 ® and ArduPilot ®.
 
-## What is an Open Design?
+> **Note** Designs are provided for a number of components used in unmanned vehicles, including: Autopilots (Flight Management Units - FMUs), ESCs (electronic speed controllers), optical flow sensors, etc.
 
-The [Pixhawk project](https://pixhawk.org/) provides open designs following the OSHW 1.1 definition.
+## What are Open Hardware Designs?
 
-Designs are (typically) specified in the form of *schematics* that show all included components (CPU, sensors, etc.), how they are connected, and their pin mappings. 
-They may also include a BOM (bill of materials).
+The [Pixhawk project](https://pixhawk.org/) provides open hardware designs following the [OSHW 1.1 definition](https://www.oshwa.org/definition/).
 
-> **Tip** A minimum design must include all information required for a manufacturer to create a hardware product that is *firmware compatible* with other hardware created to the same design.
-  This might not be a full schematic, but must include a clear pinout definition of all components, information about I2C buses (e.g. which are internally available vs what is attached internally), etc.
+In essence, this definition allows anyone to freely study, modify, distribute, make, and sell the designs (or hardware based on the designs) under the terms of a particular open source licence (you can find more about the [open source licence](#licensing) we use below).
 
-The project also delivers *reference hardware* for some open designs.
-If created, these are delivered as PCB layout files, and shared under the same [license](#licenses).
+## Hardware Designs
 
-Manufacturers are encouraged to take the open designs (and/or open reference hardware) and create firmware-compatible products that are best suited to a particular market or use case (the physical layout/form factor not part of the open specification).
+Hardware designs delivered by the project are listed below.
 
-> **Note** While a physical connector standard is not mandated, newer products generally follow the [Dronecode<sup>&reg;</sup> Autopilot Connector Standard](https://wiki.dronecode.org/workgroup/connectors/start).
+<span id="fmu_designs"></span>
+### FMU (Autopilot) Designs
 
+Pixhawk FMU open designs include all information required to create an autopilot hardware product that is *firmware compatible* with other hardware created from the same design.
+Manufacturers are encouraged to take the designs and create products that are best suited to a particular market or use case (e.g. for very small vehicles, or those that operate at environmental extremes).
 
-## Hardware Designs
+> **Note** While a physical connector standard is not mandated, newer products generally follow the [Pixhawk Connector Standard](https://pixhawk.org/pixhawk-connector-standard/).
 
-### FMU (Autopilot) Designs
 
-The project has created a number of different open designs for flight management units (autopilot hardware). 
+#### Design Format
+
+Designs are *usually* specified in the form of *schematics* that show all included components (CPU, sensors, etc.), how they are connected, and their pin mappings.
+They may also include a BOM (bill of materials).
+
+> **Note** Not all designs deliver schematics.
+
+#### Reference Hardware
+
+The project provides *reference hardware/layouts* for **some** based on some open designs, in the form of PCB layout files.
+
+These are shared under the same [license](#licenses) as the open design, and hence may be used in the same ways.
+
+#### FMU Versions
+
+The Pixhawk project has evolved the FMU design through a number of verisons.
+
 These are named using the designation: FMUvX (e.g.: FMUv1, FMUv2, FMUv3, FMUv4, etc.).
 Higher FMU numbers indicate that the board is more recent, but may not indicate increased capability (versions can be almost identical - differing only in connector wiring).
 
-The designs listed below (with a high level overview of main differences): 
+The designs listed below (with a high level overview of the main differences).
+
+Version | Description | Design | Hardware | Description
+--- | ---
+[FMUv1](FMUv1/README.md) & [IOv1](IOv1) | (Discontinued) Original Flight Management Unit and Separate I/O board.
+[FMUv2](FMUv2/README.md) | Single board with STM32427VI processor.
+[FMUv3](FMUv3_REV_D/README.md)| Identical to FMUv2, but usable flash doubled to 2MB.
+[FMUv4](FMUv4/README.md) | Increased RAM. Faster CPU. More serial ports. No IO processor
+FMUv4-PRO | Slightly increased RAM. More serial ports. IO processor.
+[FMUv5](FMUv5/README.md) | New processor (F7). Much faster. More RAM. More CAN busses. Much more configurable.<br>> **Note** Minimum specification provided (pinout info, but no schematics).
 
-- [FMUv1](FMUv1/README.md) & [IOv1](IOv1) - (Discontinued) Original Flight Management Unit and Separate I/O board.
-- [FMUv2](FMUv2/README.md) - Single board with STM32427VI processor.
-- [FMUv3](FMUv3_REV_D/README.md) - Identical to FMUv2, but usable flash doubled to 2MB.
-- [FMUv4](FMUv4/README.md) - Increased RAM. Faster CPU. More serial ports. No IO processor
-- FMUv4-PRO - Slightly increased RAM. More serial ports. IO processor <!-- is this design compatible - is it a reference? -->
-- [FMUv5](FMUv5/README.md) - New processor (F7). Much faster. More RAM. More CAN busses. Much more configurable.
-  > **Note** Minimum specification provided (pinout info, but no schematics).
 
 
 ### Sapog ESC
@@ -53,7 +71,7 @@ The designs listed below (with a high level overview of main differences):
 - [PSMv3_REV_C](PSMv3_REV_C)
 
 
-## Autopilot Products
+## Derived Autopilot Products
 
 The following boards are commercial products that are *derived* from the Pixhawk FMU designs above (information is provided here under the terms of the open source license):
 
@@ -63,15 +81,18 @@ The following boards are commercial products that are *derived* from the Pixhawk
 
 
 
-### Licensing and trademarks
+<span id="licensing"></span>
+### Licensing and Trademarks
 
 Pixhawk project schematics and reference designs are licensed under [CC BY-SA 3](https://creativecommons.org/licenses/by-sa/3.0/legalcode).
 
 The license allows you to use, sell, share, modify and build on the files in almost any way you like - provided that you give credit/attribution, and that you share any changes that you make under the same open source license (see the [human readable version of the license](https://creativecommons.org/licenses/by-sa/3.0/) for a concise summary of the rights and obligations).
 
-> **Note** Boards that are *derived directly* from Pixhawk schematic files (or reference boards) must be open sourced. They can't be commercially licensed as proprietary products.
+> **Note** Boards that are *derived directly* from Pixhawk schematic files (or reference boards) must be open sourced. 
+  They can't be commercially licensed as proprietary products.
 
-Manufacturers can create (compatible) *fully independent products* by first generating fresh schematic files that have the same pin mapping/components as the FMU designs. Products that are based on independently created schematics are considered original works, and can be licensed as required.
+Manufacturers can create (compatible) *fully independent products* by first generating fresh schematic files that have the same pin mapping/components as the FMU designs.
+Products that are based on independently created schematics are considered original works, and can be licensed as required.
 
 Product names/brands can also be trademarked. Trademarked names may not be used without the permission of the owner.