As with the specification, the milestones will need to be written using Word, Pages, or some equivalent. When submitted, it must be in PDF format. No other format will be accepted.
For small projects like this one, it is recommended that the tasks that comprise a milestone should be doable by a single software/hardware engineer.
Each milestone must contain a test/demo that, when executed, easily determines if the milestone was successfully completed. Important: this test/demo should be a go/no-go test. The outcome is pass/fail.
The schedule can be described using a graphical-drawing program, a spreadsheet, etc.