ISSUES

Known issues of Circle are:

* If you get unexpected build errors, especially from the linker, this may be
  caused by stale object files. This may happen especially after changing the
  project configuration in Config.mk, which is not detected automatically. Please
  enter "./makeall clean" from project root and "make clean" in your application's
  source directory in this case and always after changing the configuration!

* There are known issues with the included USB library (e.g. no error recovery,
  limited split support, limited isochronous support). You should only attach the
  USB devices, which are needed for your application!

* Circle is not a real-time OS. That means different simultaneous operations may
  interfere in respect of its timing behaviour. The provided samples are tested to
  work but if you try different combinations of hardware support classes this has
  to be tested by yourself. Nevertheless real-time applications based on Circle
  are possible. Have a look at doc/realtime.txt for more information!

* According to tests with the current firmware, 4K display resolutions on a
  Raspberry Pi 4 with Circle are only possible, if the option "hdmi_enable_4kp60=1"
  is enabled in the file config.txt and are not possible with the cut-down firmware
  (start_cd.elf). This may change with future firmware versions.

* sample/31-webclient does not work any more, because of the missing SSL/TLS
  support. SSL/TLS support for Circle is developed here:

	https://github.com/smuehlst/circle-stdlib

* Some modules in the addon/ subdirectory will not build with STDLIB_SUPPORT = 0.

* The class CHDMISoundBaseDevice will not link with STDLIB_SUPPORT = 0
  and AARCH = 32.

* There may be a few USB devices, which report a transfer error 3 (babble) on the
  Raspberry Pi 4. According to some comments on the Internet, this may be caused
  by incompatibilities of the USB device firmware. These devices cannot be used
  with Circle on the Raspberry Pi 4 currently.

* If there are problems to detect a specific USB device after power-on or
  attach, it may help to increase the USB power-on delay by setting the option
  usbpowerdelay= in the file cmdline.txt to 800 (ms) or higher. See the file
  doc/cmdline.txt for details!

* The class CScreenDevice does not initialize successfully on the Raspberry Pi 4,
  when a display is not attached. This is different from earlier models. To run
  most of the sample programs headless, you have to enable the system option
  SCREEN_HEADLESS in the file include/circle/sysconfig.h.

* The WLAN connection is delicate on the Raspberry Pi 5, when a HDMI display is
  used at the same time.

* The Official Touchscreen may not initialize successfully. If you have an old
  controller (v1.0), the backlight is not set by the firmware on startup. To
  resolve this set the option backlight=150 in the file cmdline.txt. See the
  file doc/cmdline.txt for details.

You can see or report further issues here:

	https://github.com/rsta2/circle/issues