add simple verify to dfu-util download

[martinmm]

Add a simple verify command that downloads the freshly flashed data and compares it to the one sent to the device.

[gautierhattenberger]

Flashing with dfu-util is already pretty long, can we have the check optional ?
On apogee boards, up to now, flashing either doesn't start (cable issue, no power,...) or succeed (with v0.7 compiled from source, better than the ubuntu packaged version 0.5).

[martinmm]

The verify only takes a couple of 100ms. The slow part is the flashing itself, not the USB transfers. A verify (as in lpc21iap) can show you that it actually succeeded.

Guess the relative slowness results from the boot ROM DFU not using x32 but x8 and/or defensive latency settings (DM00037051, 5.3.12 Memory characteristics).

[gautierhattenberger]

true, upload is fast...