# PM_GetAmpGainLevel

## Syntax

      #include <twl/spi.h>

      u32 PM_GetAmpGainLevel( u8* levelBuf );

## Arguments

levelBuf | Buffer to store the obtained results for settings values that determine the amp gain.

## Return Values

If `PM_RESULT_SUCCESS`, the command was run successfully.

If `PM_RESULT_BUSY`, the SPI was occupied by other processing and unable to process this function.

## Description

Gets the current setting for the programmable amp gain.

It saves a `u8` value in levelBuf. The values it can obtain are in the range of 0 to 119 (120 levels).

Value Stored in levelBuf | Gain
--- | ---
0 | 10.5 dB
1 | 11.0 dB
2 | 11.5 dB
: | :
n | 10.5 + (n x 0.5) dB
: | :
119 | 70.0 dB

This function uses PXI to send a command to execute the operation in question on the ARM7 processor. Once it receives that command, the ARM7 executes it by manipulating the PMIC.

About `PM_RESULT_BUSY`

The SPI is used for various other processes besides power management. If you call this function while another process is using it, this function sends a command to the ARM7. There, the SPI is determined to be BUSY, and `PM_RESULT_BUSY` is dispatched to the ARM9 without actually processing this function. Likewise, if you call this function while another PM process is running, that fact is determined on the ARM9, and this function returns `PM_RESULT_BUSY`. (In this case, the determination is made before notification is sent to the ARM7.)

Accordingly, if you want to ensure that this function succeeds, make it loop until it succeeds as shown below. (This example does not take into account mistakes such as wrong arguments.)

> Example:
> `while( PM_GetAmpGainLevel( ... ) != PM_RESULT_SUCCESS )
> {
> }`

Differences Between the `PM_GetAmpGain` and `PM_GetAmpGainLevel` Functions

There are two types of functions to get the gain settings: `PM_GetAmpGain` and `PM_GetAmpGainLevel` (this function). The former has existed since the old Nintendo DS system and can get four gain levels. (Four gain levels can be set, as well.) The latter function is explained in this reference page; it is new, has been added for the TWL system, and can get 120 gain levels.

The `PM_GetAmpGain` function can get four levels and is usable in any mode.

The `PM_GetAmpGainLevel` function can get 120 levels and is usable only in TWL hybrid and TWL limited mode. The CODEC mode decides whether 120 levels are actually configured internally. The codec is configured with 120 levels when it is running in TWL mode (this should always be TWL mode).

If 4 levels have been configured internally, this function gets a setting value that corresponds to 120 levels. On the other hand, if 120 levels have been configured internally and the `PM_GetAmpGain` function attempts to get a 4-level value, the 120 levels are divided into 4 sections from which an approximate 4-level value is returned.

The following table shows the 120-level values obtained from the `PM_GetAmpGainLevel` function when 4 levels are configured internally.

Configured Value | Gain (120 Levels)
--- | ---
`PM_AMPGAIN_20` | 31 (26.0 dB)
`PM_AMPGAIN_40` | 43 (32.0 dB)
`PM_AMPGAIN_80` | 55 (38.0 dB)
`PM_AMPGAIN_160` | 67 (44.0 dB)

The values 31, 43, 55, and 67 are given the constant definitions `PM_AMPGAIN_LEVEL_DS0`, `PM_AMPGAIN_LEVEL_DS1`, `PM_AMPGAIN_LEVEL_DS2`, and `PM_AMPGAIN_LEVEL_DS3`, respectively.

## Internal Operation

On NITRO hardware, reads the value of the PMIC register `PGA_GAIN`. On TWL hardware, reads the codec value.

## See Also

`PM_Init`
`PM_SetAmpGainLevel*`
`PM_GetAmpGain`

## Revision History

2009/06/03 Removed a description of the `PM_Init` function (because `OS_Init` is now required).
2008/08/23 Mentioned `PM_RESULT_BUSY`.
2008/05/01 Split off from `PM_GetAmpGain`.

CONFIDENTIAL