Implement Flow capacity warning status message

[DeeEmm]

Need to tidy up error and status message handling

[DeeEmm]

Removed status message reporting from API - API now only returns status via Serial link. It made no sense to have API triggering messages on the Web-UI.

Added a 'boot message'. This is the default value used for the System Status Message and will be visible in the WebUI on initial power-up. This both initialises the Message field and gives users something to tweak. BOOT_MESSAGE is defined within the configuration header file (configuration.h)

[DeeEmm]

Need to determine what message are displayed to the user via the WebUI.

• [ ] Error messages
• [ ] Status messages
• [ ] Confirmation messages

Need to determine what clears down error messages

• [ ] User confirmation
• [ ] Error remedied
• [ ] Continued operation (error ignored but no longer active)

[DeeEmm]

API Status messages were being reported to the GUI status field. This was also related to #97 where the status message was incorrectly being sent by debug.print method

Moved API status messages out of global scope and changed to serial.print method.

[DeeEmm]

Message: 'Flow limit reached'

Description: 'Test object flow exceeds Vac source capability'

Need to display to user when measured flow approaches maximum flow capability of vac source.

Also need to include config setting to set threshold Also need to be able to calibrate this value i.e. record flow with no test piece

[DeeEmm]

General status messages reviewed updated and functional.

Flow capacity warning described above not currently implemented.

[DeeEmm]

Some further thoughts on this...

Bench limits can be determined by testing the reference depression. If depression cannot be maintained when increasing flow requirements the bench has reached it's limit. This can be used to determine the flow limit for the bench.

There's essentially two ways I can see this working

1. A range of orifices can be measured to determine what the maximum achievable flow is for a given reference pressure. This flow value can then be 'hard coded' by manually entering it as a configuration parameter.
2. The depression value can be compared to vacuum control 'on-the-fly'. Limit is reached when vacuum control is at or approaching 100% modulation, but reference pressure cannot be maintained

Basically if the reference depression cannot be maintained for a given flow rate, then test piece is outflowing the vac source.

There are two ways to set this up:

1. Manually enter the calculated / measured limit and then compare flow rate to this limit. i.e. if flow_rate >= flow_rate_limit
2. Test limit 'on-the-fly' by comparing vac_speed_ref to ref_pressure. This does not require any specific limit to be measured or set and works for all depressions / flow rates

Option 2 is more flexible but requires integrated vac speed control. Option 1 will work for any setup but requires that the user sets up the initial flow limit.

[DeeEmm]

Additionally. To determine absolute bench limits

With vac source at 100% Gradually decrease test orifice size until desired depression is reached The resultant flow value is the max flow the bench can measure (for the given depression / enviro conditions)