USB stdio v2 #349
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USB stdio v2 #349
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It is possible for print functions to raise an exception, so we need to catch this when printing a final exception since the nlr stack is empty at that point and would otherwise cause a crash.
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Move the stdin buffer from pbsys/bluetooth to pbsys/host so that it can be used by other host interfaces, such as USB stdio. All connections will share the same stdin buffer. All function names are renames from "rx" to "stdin" to reflect the current usage. The "rx" naming was a holdover from when this was originally only used for Bluetooth RX via the Nordic UART Service. A new PBSYS_CONFIG_HOST_STDIN_BUF_SIZE option is introduced to set a platform-specific buffer size. Bluetooth-only hubs continue to use the same size that was used in pbsys/bluetooth. Hubs with USB are set to 64 bytes to match the USB endpoint size.
Fix issue with pbsys_host_stdout_write() not being cancellable. The static state variables in the function required that the function be called repeatedly until it returned something other than PBIO_ERROR_AGAIN. However, in MicroPython, an exception may be raised in between calls, which would leave the state variables in an inconsistent state causing incorrect behavior on the next call. We can save code size on platforms that only have one transport by only calling the relevant function instead of trying to duplicate the stream to a non-existent transport. Then, to handle platforms with multiple transports, rework the logic to be able to send data to multiple transports without having to maintain state between calls. This is done by ensuring that we only send the same amount of data to each transport.
Implement the Pybricks Profile event subscription flag. This saves us from trying to send messages to the host when there is no app running to receive them. Previously, trying to write to stdout would block forever because of this. The 5 millisecond timeout is arbitrary. Wireshark shows that the OUT endpoint is being serviced in less than 1 ms, so this should be plenty of time even if some hosts are an order of magnitude slower. We don't want to make it too big because it will delay user programs for this long and we don't want to mess up someone's control loop too badly.
Now that USB is mostly working, we can enable it by default on SPIKE Essential and Prime hubs.
Add an extra check to make sure USB data has been sent before as well to pbsys_host_tx_is_idle() if applicable. Also document the function while we are here.
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The less ambitious alternative to #332.
This time, instead of duplicating a bunch of stuff, we finish the TODO to move the stdin buffer out of pbsys_bluetooth and into pbsys_host. Then we can hook up the USB stdin to this as well.