Update README.md

Updated the custom firmware FAQ answer with the latest progress notes. Replaced the bootloader bug FAQ with a more generic FAQ covering the main situations under which the SF2000 fails to boot correctly. Added a brief note on the mysterious new `August 3rd` BIOS that has started appearing on some newer devices.

README.md

@@ -15,7 +15,7 @@ This document is a collection of notes and information I've made about the devic
     - [How do I install new menu themes?](#how-do-i-install-new-menu-themes)
     - [How do I change the four shortcuts/games listed on each system's main menu page?](#how-do-i-change-the-four-shortcutsgames-listed-on-each-systems-main-menu-page)
     - [SNES games run really slowly... what's wrong?](#snes-games-run-really-slowly-whats-wrong)
-    - [Help! I was doing stuff in the bios folder or trying to install a new firmware, and now my SF2000 won't turn on, or is stuck at a black screen!](#help-i-was-doing-stuff-in-the-bios-folder-or-trying-to-install-a-new-firmware-and-now-my-sf2000-wont-turn-on-or-is-stuck-at-a-black-screen)
+    - [Help! My SF2000 won't turn on, or is stuck at a black screen!](#help-my-sf2000-wont-turn-on-or-is-stuck-at-a-black-screen)
     - [When I connect the SF2000 to a TV via the A/V cable, the sound is very quiet/low - is that normal?](#when-i-connect-the-sf2000-to-a-tv-via-the-av-cable-the-sound-is-very-quietlow---is-that-normal)
     - [Game saves don't seem to be working for me? Save states are fine, but the built-in save function in games doesn't seem to work?](#game-saves-dont-seem-to-be-working-for-me-save-states-are-fine-but-the-built-in-save-function-in-games-doesnt-seem-to-work)
     - [I have a question that isn't answered here... who or where do I ask?](#i-have-a-question-that-isnt-answered-here-who-or-where-do-i-ask)
@@ -69,7 +69,7 @@ Some downsides to the device: it's mono only (you only get the left-channel audi
 So is the "Data Frog" any good? Only you can answer that question for yourself. There are certainly more powerful devices out there, more fully featured devices, devices with better hardware, etc. - but almost all of those devices cost a lot more than the SF2000. At the end of the day, you have to look at the features offered at the given price-point, and only then can you decide if you're interested in the device or not.
 
 ### Is there any custom firmware?
-As of August 4th 2023, **no**, not yet. However efforts are underway; an SDK for the CPU has been identified, and custom firmware is now in the very early stages of development. Most recently, folks working on the firmware have been focussing on various aspects simultaneously; there have been efforts to get SDL support operational (SDL is a multimedia library that's used by several Retroarch cores), work is being done on the display driver to improve compatibility with various display formats requested by cores (e.g., XRGB8888) and to improve performance, and improvements to their toolchain - both attempting to create a reliable way to capture hard-crashes of the SF2000 to aid in debugging, as well as simplifying the build environment (the SDK as downloaded is quite messy/complex). Several individual cores have already been experimentally compiled; results thus far have varied. Some have functioned correctly, albeit at slow speeds; others have failed to run entirely. Most have crackly/broken audio due to running below correct speed, and some have no sound at all. Input problems with some cores have also been reported. The cores are individual cores, built as entire firmwares in their own right - there is currently no way to "switch" between cores without taking the microSD card out of the SF2000 and replacing the firmware with one built to contain a different core. Work on allowing the core to be switched by some mechanism is also an area of focus for future work by the devs.
+As of August 19th 2023, **no**, not yet. However efforts are underway; an SDK for the CPU has been identified, and custom firmware is now in the very early stages of development. Most recently, folks have been experimenting with trying to build different Retroarch cores, both to see if they build at all, and if they do, to see what their performance is like on the SF2000. Results thus far have varied. Some have functioned correctly, albeit at slow speeds; others have failed to run entirely. Most have crackly/broken audio due to running below correct speed, and some have no sound at all. Input problems with some cores have also been reported. The cores are individual cores, built as entire firmwares in their own right - there is currently no way to "switch" between cores without taking the microSD card out of the SF2000 and replacing the firmware with one built to contain a different core. Work on allowing the core to be switched by some mechanism is also an area of focus for future work by the devs.
 
 [A GitLab repo](https://git.maschath.de/ignatz/hcrtos) has been set up by `ignatzdraconis` for the work, and you can follow along with discussion in the [`Retro Handhelds` Discord server](https://discord.gg/retrohandhelds) (specifically, in the `🐸data_frog_sf2000` channel there's a `SF2000 Dev` thread where most of the tech talk and details are posted first). Note that any cores currently built should be considered highly experimental, and are not vetted to be "safe" to run (e.g., current builds may push the hardware of the SF2000 to its operational limits do to optimisation issues, and may incur thermal damage to the device if left running for too long, etc.).
 
@@ -103,8 +103,12 @@ Recent versions of [Tadpole](https://github.com/EricGoldsteinNz/tadpole) by `.er
 ### SNES games run really slowly... what's wrong?
 There's a bug in all stock firmware versions later than the original mid-March firmware which often causes SNES games to run really slowly on first launch (and their sound is slow and lower pitch too); this only impacts SNES. Usually this can be corrected by launching the game, then quitting back to the game selection menu via `START + SELECT`, and then immediately re-launching the game again. Note however that the stock firmwares do also struggle a bit with SNES emulation in general, so any additional slowdown after the second launch is just what you get.
 
-### Help! I was doing stuff in the bios folder or trying to install a new firmware, and now my SF2000 won't turn on, or is stuck at a black screen!
-You've probably run into the bootloader bug - you can [find the two fixes to it below](#bootloader-bug). Alternatively, [follow Data Frog's instructions](https://www.youtube.com/watch?v=j8dT2fdGfck) to wipe your microSD card and flash a clean firmware image.
+### Help! My SF2000 won't turn on, or is stuck at a black screen!
+The three most likely causes for this are:
+
+* If you've switched to using a different microSD card than the one your SF2000 switched with, there's a good chance the new microSD card you're using is not compatible with the SF2000. The device seems to be very picky about the types of microSD cards it will or won't read. Try putting your original microSD card back into the SF2000 and see if it'll boot OK from that.
+* If you've done anything at all to the `bios` folder on the microSD card (_anything_ at all), then there's a good chance you've run into the bootloader bug - you can [find the two fixes to it below](#bootloader-bug). Alternatively (or if neither of the two fixes work for you), [follow Data Frog's instructions](https://www.youtube.com/watch?v=j8dT2fdGfck) to wipe your microSD card and flash a clean firmware image.
+* Your battery could be running low. The SF2000 will still "turn on" when its battery is low on charge (the red light will still come on), but the device itself will actually fail to boot, just leaving you with a black screen. Turn the device off, and charge it fully (the stock battery takes 3.5 hours to charge from empty - the green charging light will not go out, so you'll have to time it yourself).
 
 ### When I connect the SF2000 to a TV via the A/V cable, the sound is very quiet/low - is that normal?
 It's "normal" for newer versions of the firmware, anyway! Older firmware versions had no issues with audio volume via A/V, but at least the `05.22` version does. `Zerter#4954` from Discord found a workaround:
@@ -247,6 +251,8 @@ Known firmware versions are currently (dates approximate):
 | May 15th | ? | Added a built-in UI for global button mapping (which is broken in several ways, mainly SNES and Genesis controls are swapped, and no support for setting Player 2 controls), added a History feature, added a Favourites feature |
 | May 22nd | 1.5V | First firmware with an official version number. Fixed the SNES/Genesis swapped button mappings, and now sets Player 2 controls to be identical to Player 1 (no way to set independently). There's some evidence of undocumented emulation improvements; some GBA homebrew that was non-functional in previous firmwares now loads correctly, and some GBA titles see marginally improved performance |
 
+There's a new firmware that has started appearing on some devices delivered to folks around the end of July, beginning of August 2023 that seem to have a different BIOS on them than any of the four above; I'm dubbing this BIOS the `August 3rd` or `08.03` BIOS as that was when its MD5 hash was first posted to the Retro Handhelds Discord server. Currently, little is know about this BIOS revision, including whether or not it's official; at least initially it appears to be very similar to the May 22nd revision.
+
 Custom firmware (CFW) is currently in the very early stages of development (see [here](#is-there-any-custom-firmware)). In the meantime, the stock firmware has been investigated quite a bit; here are some findings from it:
 
 ### Bootloader Bug
@@ -602,6 +608,8 @@ All of these are linked above already in their relevant sections, but just in ca
 ---
 
 ## Version History
+- `20230819 - 1.34`: Updated the custom firmware FAQ answer with the latest progress notes. Replaced the bootloader bug FAQ with a more generic FAQ covering the main situations under which the SF2000 fails to boot correctly. Added a brief note on the mysterious new `August 3rd` BIOS that has started appearing on some newer devices.
+
 - `20230804 - 1.33`: Updated the custom firmware FAQ answer with the latest progress notes.
 
 - `20230730 - 1.32`: Added a link to "ZFBTool" by `dteyn` in the "Tools and Links" section. Updated the custom firmware FAQ answer with the latest progress notes.