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Sweetberry USB power monitoring

This tool allows high speed monitoring of power rails via a special USB endpoint. Currently this is implemented for the Sweetberry board.

To use on a board, you'll need two config files, one describing the board, a .board file, and one describing the particular rails you want to monitor in this session, a .scenario file.

Converting from servo_ina configs

Method 1 (not limited to chroot)

Many configs can be found for the servo_ina_board in hdctools/servo/data/. Sweetberry is plug compatible with servo_ina headers, and config files can be converted with the following tool:
```
./convert_servo_ina.py <board>_r0_loc.py
```
This will generate <board>_r0_loc.board and <board>_r0_loc.scenario locally, which can be used with powerlog.py.
Method 2 (recommended for Chrome OS developers, requires chroot)

If you are using powerlog.py within the chroot, copy <board>_r0_loc.py to src/third_party/hdctools/servo/data, then add this line to file:
```
config_type = 'sweetberry'
```
And run command in chroot:
```
(Anywhere in chroot, just ONCE) cros_workon --host start dev-util/hdctools
```
Then every time you make a change to <board>_r0_loc.py, run:
```
(Anywhere in chroot) sudo emerge dev-util/hdctools
```
The command will install the corresponding .board and .scenario file in the chroot. To use powerlog.py use the command:
```
(Anywhere in chroot) powerlog -b <board>_r0_loc.board -c <board>_r0_loc.scenario
```
There is no need to specify the absolute path to the .board and .scenario file, once they are installed into the chroot. If there is any changes to <board>_r0_loc.py, you need to sudo emerge dev-util/hdctools again.

Board files

Board files contain a list of rails, supporting 48 channels each on up to two Sweetberries. For each rail you must specify a name, sense resistor value, and channel number. You can optionally list expected voltage and net name. The format is as follows, in json:

example.board:

[
{ "name": "railname",
  "rs": <sense resistor value in ohms>,
  "sweetberry": <"A" for main Sweetberry, "B" for a secondary Sweetberry>,
  "channel": <0-47 according to board schematic>,
  "v": <optional expected bus voltage in volts>,
  "net": <optional schematic net name>
},
{...}
]

Scenario files

Scenario files contain the set of rails to monitor in this session. The file format is simply a list of rail names from the board file.

Optionally, you can specify the type of measurement, from the set of "POWER", "BUSV", "CURRENT", "SHUNTV". If not specified, the default is power.

example.scenario:

[
"railname",
"another_railname",
["railname", "BUSV"],
["railname", "CURRENT"],
...
]

Output

powerlog.py will output a csv formatted log to stdout, at timing intervals specified on the command line. Currently values below -t 10000 do not work reliably but further updates should allow faster updating.

An example run of:

./powerlog.py -b board/marlin/marlin.board -c board/marlin/marlin_short.scenario -t 100000

Will result in:

ts:32976us, VBAT uW, VDD_MEM uW, VDD_CORE uW, VDD_GFX uW, VDD_1V8_PANEL uW
0.033004, 12207.03, 4882.81, 9155.27, 2441.41, 0.00
0.066008, 12207.03, 3662.11, 9155.27, 2441.41, 0.00
0.099012, 12207.03, 3662.11, 9155.27, 2441.41, 0.00
...

The output format is as follows:

ts:32976us

Timestamps either zero based or synced to system clock, in seconds. The column header indicates the selected sampling interval. Since the INA231 has specific hardware defines sampling options, this will be the closest supported option lower than the requested -t value on the command line.
VBAT uW

Microwatt reading from this rail, generated on the INA by integrating the voltage/amperage on the sense resistor over the sampling time, and multiplying by the sampled bus voltage.
... uW

Further microwatt entry columns for each rail specified in your scenario file.
... xX

Measurement in uW, mW, mV, uA, uV as per config.

Calculate stats and store data and stats

When appropriate flag is set, powerlog.py is capable of calculating statistics and storing statistics and raw data.

Example 1
```
./powerlog.py -b board/eve_dvt2_loc/eve_dvt2_loc.board -c board/eve_dvt2_loc/eve_dvt2_loc.scenario --save_stats [<directory>]
```
If <directory> is specified, this will save stats as: <directory>/sweetberry<timestemp>/summary.txt. If <directory> does not exist, it will be created.

If <directory> is not specified but the flag is set, this will save stats under the directory which powerlog.py is in: <directory of powerlog.py>/sweetberry<timestemp>/summary.txt.

If --save_stats flag is not set, stats will not be saved.
Example 2
```
./powerlog.py -b board/eve_dvt2_loc/eve_dvt2_loc.board -c board/eve_dvt2_loc/eve_dvt2_loc.scenario --save_raw_data [<directory>]
```
If <directory> is specified, this will save raw data in: <directory>/sweetberry<timestemp>/raw_data/. If <directory> does not exist, it will be created.

If <directory> is not specified but the flag is set, this will save raw data under the directory which powerlog.py is in: <directory of powerlog.py>/sweetberry<timestemp>/raw_data/.

If --save_raw_data flag is not set, raw data will not be saved.
Example 3:
```
./powerlog.py -b board/eve_dvt2_loc/eve_dvt2_loc.board -c board/eve_dvt2_loc/eve_dvt2_loc.scenario --save_stats_json [<directory>]
```
If <directory> is specified, this will save MEANS in json as: <directory>/sweetberry<timestemp>/summary.json. If <directory> does not exist, it will be created.

If <directory> is not specified but the flag is set, this will save MEANS in json under the directory which powerlog.py is in: <directory of powerlog.py>/sweetberry<timestemp>/summary.json.

If --save_stats flag is not set, stats will not be saved.

--save_stats_json is designed for power_telemetry_logger for easy reading and writing.

Making developer changes to `powerlog.py`

powerlog.py is installed in chroot, and the developer can import powerlog or use powerlog directly anywhere within chroot. Anytime the developer makes a change to powerlog.py, the developer needs to re-install powerlog.py so that anything that imports powerlog does not break. The following is how the developer installs powerlog.py during development.

Run command in chroot:

(Anywhere in chroot, just ONCE) cros_workon --host start chromeos-base/ec-devutils
(Anywhere in chroot, every time powerlog.py is changed) sudo emerge chromeos-base/ec-devutils

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