Update README with USB device prerequisites

README.md

@@ -1,15 +1,15 @@
 # psa-update
 
-CLI alternative to PSA (Peugeot / Citroën / DS / Opel) infotainment system update (NAC / RCC firmware and navigation maps),
-hopefully more robust.
+CLI alternative to PSA (Peugeot / Citroën / DS / Opel) infotainment system update (NAC / RCC firmware and navigation maps), hopefully more robust.
 
 ![Screenshot](screenshot.png)
 
-`psa-update` offers mostly the same features as the official firmware/map update application proposed by the car vendor,
-except that it does not format the USB device that has to be used to upload the firmware/map update to the car. Updates
-are exclusively downloaded from the official PSA site.
+`psa-update` offers mostly the same features as the official firmware/map update application proposed by the car vendor, except that it does not format the USB device that has to be used to upload the firmware/map update to the car.
+
+Updates are exclusively downloaded from the official PSA site.
 
 Features:
+
 - Download updates of RCC / NAC firmwares, and navigation maps (NAC only)
 - Resume downloads in case of failure
 - Prepares USB flash drive for car infotainment system update
@@ -18,29 +18,45 @@ Features:
 ## Usage
 
 The command line executable can be invoked in a terminal:
+
 ```shell
 $ psa-update
 ```
+
 This will interactively ask for vehicle VIN, check for available NAC/RCC/map updates, and extract updates to a USB flash drive.
 
 Once copied to the USB drive, the update can be applied on the infotainment system following PSA instructions.
-For example for Peugeot:
+
+For exemple for Peugeot:
+
 - [RCC instructions](https://web.archive.org/web/20220719220945/https://media-ct-ndp.peugeot.com/file/38/2/map-software-rcc-en.632382.pdf)
 - [NAC instructions](https://web.archive.org/web/20230602131011/https://media-ct-ndp.peugeot.com/file/38/0/map-software-nac-en.632380.pdf)
 
 ## Requirements
 
+For the transfer of updates to the car, a USB device is required:
+
+- Recommended size is **32 GB**. Although most updates are smaller than 16 GB, some navigations maps can be larger than 16 GB.
+- It must be formatted as **FAT32**.
+
+> Note: When using Windows, if the USB device is larger than 32 GB, it is not possible to format it using FAT32. Alternatives are:
+>
+> - Create a 32 GB partition and format if as FAT32 and leave the rest unformatted.
+> - Use a third-party tool to format the USB device using FAT32. The official vendor application presumably uses [fat32format from Ridgecrop Consultants Ltd](http://ridgecrop.co.uk/index.htm?guiformat.htm) to achieve this.
+
 On Linux, OpenSSL is required. On Windows and MacOS, nothing is required, the operating system TLS framework is used.
 
 ## Install
 
 Binaries are available for Windows (x86-64), Linux (x86-64) and MacOS (x86-64 and AArch64/ARM64) in the [releases](https://github.com/zeld/psa-update/releases) section.
+
 To install, simply download and extract the `psa-update` executable.
 For other platforms the project can be built from source code (see below).
 
 ## Build from source
 
 To build and run from source code using stable rust compiler toolchain (version 1.81+):
+
 ```shell
 $ git clone https://github.com/zeld/psa-update.git
 $ cargo run
@@ -49,26 +65,31 @@ $ cargo run
 ## Proxy
 
 Download is possible behind a proxy provided the `http_proxy` and `https_proxy` environment variables are correctly set.
-In a Linux or MacOS shell:
+
+Using a Linux or MacOS terminal:
+
 ```shell
 export http_proxy=<host>:<port>
 export https_proxy=<host>:<port>
 ```
-In a Windows CMD prompt:
+
+Using a Windows CMD prompt:
+
 ```cmd
 SET http_proxy=<host>:<port>
 SET https_proxy=<host>:<port>
 ```
 
 ## Logging
 
-Logging can be enabled using the `RUST_LOG` variable. For example to enable `debug` log level:
+Logging can be enabled using the `RUST_LOG` variable. For exemple to enable `debug` log level:
+
 ```shell
 RUST_LOG="debug" ./psa-update
 ```
 
 ## Credits
 
-- Inspired from the Linux script in this french [forum post](https://www.forum-peugeot.com/Forum/threads/app-peugeot-update-logiciel-alternatif-multi-os-v1-5-26-08-2021.119707/)
-- For the list of navigation maps, and associated content, this french [forum post](https://forum-auto.caradisiac.com/topic/129967-le-nac-du-3008-ii-et-de-tous-les-v%C3%A9hicules-psa-lisez-en-premier-la-page-n%C2%B012/)
+- Inspired from the Linux script in this French [forum post](https://www.forum-peugeot.com/Forum/threads/app-peugeot-update-logiciel-alternatif-multi-os-v1-5-26-08-2021.119707/)
+- For the list of navigation maps, and associated content, this French [forum post](https://forum-auto.caradisiac.com/topic/129967-le-nac-du-3008-ii-et-de-tous-les-v%C3%A9hicules-psa-lisez-en-premier-la-page-n%C2%B012/)
 - List of firmware and map updates on [this site](https://sites.google.com/view/nac-rcc/)