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Fixes #197, see there for a detailed description of the problem this PR is trying to address.
Proposed solution
As described in #197, the problem is likely caused by the firmware using the instantaneous carriage direction as given by the belt encoder to determine which of the active carriage's two "needle selectors" to consider when trying to determine whether the current row of knitting is complete.
With this PR, we instead maintain a "current line direction" variable (
m_currentLineDirection) that stores the expected direction of carriage travel for the current line, regardless of its immediate physical movement. This variable is initialized when knitting starts based on which Hall sensor was last passed, and flipped every time we detect a line is complete, as we request the next line from the computer.To detect that a line is complete, instead of using a flag (
m_workedOnLine) that alternates betweentrueandfalse, we use the current line direction to know whether to expect the carriage on the left or right end of the working area. This more securely guarantees that we don't trigger multiple end-of-row events while staying on the same end of the bed.The precise determination of the row being done is also improved. Not only do we check for the active needle selector (e.g. the one on the left side of the K carriage when moving right, or the one on the right side of the garter carriage also when moving right) to be past the last needle in work, we also check for the inactive needle selector to be past the last working needle.
Why is this important?
Let's look at a (schematized) K carriage moving right, hence with its active needle selector on the left side:
Once the active needle selector gets past the last needle in work, we're ready to turn around and start the new row (with the active and inactive selectors switching roles):
So far, so good. But what about a garter carriage in the same situation?
After a while, the active needle selector will have worked on the last active needle:
But if we were to turn the carriage around at this point, the newly-active selector would have missed a number of needles from the right end of the working area!
Therefore, it is imperative to wait for the inactive selector to pass the last needle, so that when it becomes active it can get started on what is now the first needle of the next row:
Waiting at both needle selectors to pass the last needle is a solution that works for both types of carriage, therefore this is what is implemented in this PR.