doc: add pictures

README.md

@@ -1,19 +1,74 @@
-The USB micro-B and C cable tester identifies capabilities supported by USB cables and deduces it's purpose.
+The USB micro-B and C cable tester identifies capabilities supported by USB cables and deduces their purpose.
 It helps figuring out if a USB cable is for charging or to transfer data, and at which speed.
 It supports type A to micro-B, A to C, and C to C USB cables.
 
+<img src="picture/front.webp" title="front" height="250"/>
+<img src="picture/back.webp" title="back" height="250"/>
+
 usage
 =====
 
-- ensure the tester has a non-empty battery in the CR2032/2025, or is externally powered through the USB power port
+- ensure the tester has a non-empty battery in the CR2032/2025 slot, or is externally powered through the USB power port
 - plug one end of the cable in one of the host ports
 - plug the other end of the cable in one of the devices ports
-- if using a battery, press on the BAT ON button
+- when using a battery, press on the BAT ON button
 - the tester will identify the cable's capabilities, on the left side
 - the tester will then show the cable's purpose, on the right side
 
+Once I know it's purpose, I mark the cables with a letter:
+
+- USB A to micro-B only with ground and VBUS wires, limiting power transfer to 0.5 since they can't indicate battery charge: **P**
+<img src="picture/a-b-p.webp" title="front" width="500"/>
+- USB A to micro-B, with data line shorted internally to indicate 1.5A battery charge (even when not sure the host supports it): **C**
+<img src="picture/a-b-c.webp" title="front" width="500"/>
+- USB A to micro-B with data wires, but error prone since not shielded (sufficient for low speed): **D**
+<img src="picture/a-b-d.webp" title="front" width="500"/>
+- USB A to micro-B with shielded data wires (good for high speed): **S**
+<img src="picture/a-b-s.webp" title="front" width="500"/>
+- USB A to C without data lines but battery charge indication: **C**
+<img src="picture/a-c-c.webp" title="front" width="500"/>
+- USB A to C with unshielded data lines: **D**
+<img src="picture/a-c-d.webp" title="front" width="500"/>
+- USB A to C with SuperSpeed data lines, and shielded: **3**
+<img src="picture/a-c-3.webp" title="front" width="500"/>
+- USB A to C with SuperSpeed data lines, but unshielded: **D**
+<img src="picture/a-c-sd.webp" title="front" width="500"/>
+- USB C to C with shielded data lines: **S**
+<img src="picture/c-c-s.webp" title="front" width="500"/>
+- USB C to C with electronic marking allowing 5A charging: **C**
+<img src="picture/c-c-c.webp" title="front" width="500"/>
+- USB C to C with all features: **F**
+<img src="picture/c-c-f.webp" title="front" width="500"/>
+
+The tester can detect electronically marked C to C cables.
+Often they are present (and required) in cables allowing 5A/100W charging.
+But to be sure, one should read the capabilities from the chip, which is not supported by the tester.
+Full Feature C to C cable also require electronical marking, but could only support 3A charging.
+Because of that the 3A and 5A indicators are on at the same time (when the marking can be just for the features).
+
 To understand further the capabilities and purpose of a cable, I recommend reading the USB specification, mainly the one for the [type-C connector](https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-23).
 
+report
+------
+
+There is a UART output on the debug port.
+The analysis of the capabilities to the purpose is periodically output on it.
+You can connect to it and view it using the 115200 8N1 baud rate.
+
+firmware
+--------
+
+You can flash or update the firmware using the SWD signals on the debug port, of also use the UART signals and the bootloader.
+To start the bootloader, press and hold the BL button while shortly pressing the RST button.
+You can then use [stm32flash](https://github.com/stm32duino/stm32flash):
+
+~~~
+stm32flash -w binray.hex -v /dev/ttyACM0
+~~~
+
+The compiled binary is available in the release archives.
+The source code of the firmware is in the `firmware` folder.
+
 design choice
 =============
 
@@ -29,12 +84,12 @@ do:
 - battery operated: it's a very simple device, and this avoids needing to require external power
 - power port: in case you have no battery or it runs out
 - USB 3.0: because it is hard to identify if C-C cable support SuperSpeed
-- purpose: deduce from capabilities
+- purpose: deduce from capabilities for users not knowledgable in USB cables
 
 don't:
 
 - small: no need to build it as compact as possible
-- A or micro-B 3.0: the connectors that support it are obvious, and it's rare they are used for anything else than Super-Speed transfer (plus they are less common or problematic)
+- A to micro-B 3.0: the connectors that support it are obvious, and it's rare they are used for anything else than Super-Speed transfer (plus they are less common or problematic)
 - Power Delivery capabilities: this requires complex host software communicating with the eMarker chip in the cable
 - OTG: even if detecting this functionality is easy, micro-B OTG adapters are not popular anymore
 - impedance: only the presence of wires is tester, not their impedance
@@ -47,8 +102,8 @@ Some additional tests verify the resistances in the plugs.
 For more details, check the schematic, and refer to [type-C specification](https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-23).
 
 The left side identifies the capabilities.
-Based on that, a micro-controller (MCU) with map the combination into a purpose on the right side.
-The left side if independent of the MCU and right side.
+Based on that, a micro-controller (MCU) will map the combination into a purpose on the right side.
+The left side is independent of the MCU and right side.
 
 limitation
 ----------