# meter Module 

| Status | Last Update | API Version |
| ------ | ------ | ------ |
| Active | 2019-11-14 | V1.00.00 |

## Description
 Access the on-board voltage & current meter.
 
## meter.setDataSource()
### Description
Set the data source of the readings.


### Parameters

| Name | Type | Range | Usage |
| ------ | ------ | ------ |  ------ |
| <dataSource> | number| meter.INSTANT meter.FILTERSTAGE1 meter.FILTERSTAGE2 |Specify the data-source|

- `meter.INSTANT`: Set the reading to INSTANT, which updates every 1ms without any filtering.
- `meter.FILTERSTAGE1` : Set the reading to FILTERSTAGE1, this stage is the average of the `meter.INSTANT` readings, but the average time is defined by user, it is recommended for display purposes.
- `meter.FILTERSTAGE2` : Set the reading to FILTERSTAGE2, this stage is filtered again based on `meter.FILTERSTAGE1` readings, it is recommended for display purposes which require stable readings.

If it is not for display purposes, it's recommended to use `meter.INSTANT` as the data-source, as it provides fast and precise enough readings for most cases. Update rate of `meter.FILTERSTAGE1` and `meter.FILTERSTAGE2` are dependent on user settings.

### Return value
nil
### Example call
```lua
meter.setDataSource(meter.INSTANT)
```

## meter.readVoltage()
### Description
Get voltage reading of the meter in volts.

### Parameters
nil
### Return value

| Name | Type | Range | Usage |
| ------ | ------ | ------ |  ------ |
| voltage | number| 0~36 |Voltage reading|

### Example call
```lua
voltage = meter.readVoltage()
```

## meter.readCurrent()
### Description
Get current reading of the meter in amps. Notice that for display convenience, it returns the absolute value. If you want to get the current direction, call `meter.readCurrentDirection()`.

### Parameters
nil
### Return value

| Name | Type | Range | Usage |
| ------ | ------ | ------ |  ------ |
| current | number| 0~6 |Current reading|

### Example call
```lua
current = meter.readCurrent()
```

## meter.readPower()
### Description
Get current reading of the meter in watts. Notice that for display convenience, it returns the absolute value. 

### Parameters
nil
### Return value

| Name | Type | Range | Usage |
| ------ | ------ | ------ |  ------ |
| power | number| 0~216 |Power reading|

### Example call
```lua
power = meter.readPower()
```
## meter.readDP()
### Description
Get voltage reading of the USB DP in volts.

### Parameters
nil
### Return value

| Name | Type | Range | Usage |
| ------ | ------ | ------ |  ------ |
| v_dp | number| 0~3.3 |DP Voltage reading|

### Example call
```lua
dp = meter.readDP()
```

## meter.readDM()
### Description
Get voltage reading of the USB DM in volts.

### Parameters
nil
### Return value

| Name | Type | Range | Usage |
| ------ | ------ | ------ |  ------ |
| v_dm | number| 0~3.3 |DM Voltage reading|

### Example call
```lua
dp = meter.readDM()
```
## meter.readCurrentDirection()
### Description
Get direction of the current. Returns true if the direction is reversed, which is, the current goes from the output port back into the input port and vice versa.

### Parameters
nil
### Return value

| Name | Type | Range | Usage |
| ------ | ------ | ------ |  ------ |
| dir | boolean|  |Direction|

### Example call
```lua
dir = meter.readCurrentDirection()
```