DCM224 values and units aren't synchronised on front panel

[brianbienvenu]

When driving a noisy/peaky load like a stepper motor driver, the DCM224 front panel current readout isn't consistent.

Here's a short video showing the issue: https://www.dropbox.com/s/r5a9zkj52qxuub2/2021-11-02%2017.54.50.mp4?dl=0

Clearly the power calculation is operating from a different internal current readout value, as it doesn't vary as widely.

Below is a list of current values shown on the screen from the start of the capture:

770.0  mA
610.0  mA
740.0  mA
520.0   A
460.35 mA
730.35 mA (briefly, half update)
730.0  mA
1.0    mA
670.0   A
550.0  mA (briefly, half update)
550.09 mA
530.09 mA (briefly, half update)
530.0  mA
840.0  mA
970.0  mA
970.3  mA
790.3  mA 
790.3   A  (briefly, half update)
790.0   A
470.0  mA

[prasimix]

Copy of the video:

https://user-images.githubusercontent.com/15106476/139808593-f3ec53d3-858e-4bed-bd22-f4990505746e.mp4