them symbolic constants.
- A timeout is 0
- A missing driver is 65534
- An invalid channel is 65535
ManualControl: Make it deal with the values explicitly. A timed out value
should not be treated like a minimum duration signal. Instead it does not
updated the scaled value but marks the data window as invalid to trigger the
failsafe.
Allocate per-instance data for drivers from the heap
rather than as static variables from the .data segment.
This converts > 800 bytes of RAM from being always consumed
as static data into being allocated from the heap only when
a particular feature is enabled in the hwsettings object.
A minimal config (no receivers, flexi port disabled, main port
disabled) leaves 2448 bytes of free heap. That's our new baseline.
Approximate RAM (heap) costs of enabling various features:
+ 632 Serial Telemetry (includes 400 bytes of Rx/Tx buffers)
+ 108 PWM Rcvr
+ 152 PPM Rcvr
+ 112 Spektrum Rcvr
+ 24 S.Bus (Should be closer to 68 since driver is still using
static memory)
There are still some drivers that pre-allocate all of their memory
as static data. It'll take some work to convert those over to
dynamically allocating their instance data.
This allows the spektrum and sbus receiver drivers to bind
directly to the usart layer using a properly exported API
rather than overriding the interrupt handler.
Bytes are now pushed directly from the usart layer into the
com layer without any buffering. The com layer performs all
of the buffering.
A further benefit from this approach is that we can put all
blocking/non-blocking behaviour into the COM layer and not
in the underlying drivers.
Misc related changes:
- Remove obsolete .handler field from irq configs
- Adapt all users of PIOS_COM_* functions to new API
- Fixup callers of PIOS_USB_HID_Init()
Each channel was previously tracking a separate driver.
Now, channels are grouped within a channel group to save
RAM used for tracking and to better reflect how channels
are actually mapped.
