# PM_GetAmpGain

## Syntax

      #include <nitro/spi.h>

      u32 PM_GetAmpGain( PMAmpGain* gainBuf );

## Arguments

gainBuf | 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.

A `PMAmpGain` enumerated type value will be saved in gainBuf. It will be one of the following four values.

Value Stored in gainBuf | Gain
--- | ---
`PM_AMPGAIN_20` | 26.0 dB (20x)
`PM_AMPGAIN_40` | 32.0 dB (40x)
`PM_AMPGAIN_80` | 38.0 dB (80x)
`PM_AMPGAIN_160` | 44.0 dB (160x)

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.

When gain is configured to 120 levels internally, this function will return a value corresponding to the internally set value, as shown below.

Value Stored in gainBuf | Gain (120 levels)
--- | ---
`PM_AMPGAIN_20` | 0-36 (10.5-28.5 dB)
`PM_AMPGAIN_40` | 37-48 (29.0-34.5 dB)
`PM_AMPGAIN_80` | 49-60 (35.0-40.5 dB)
`PM_AMPGAIN_160` | 61-119 (41.0-70.0 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. Therefore, this function may not operate instantly after you call it. Before you use this function, use the `PM_Init` function to initialize the PM library. (The `PM_Init` function has to be called only once. Also, when you call the `OS_Init` function, there is no need to call the `PM_Init` function separately because it is called from inside `OS_Init`.)

This function can be used from an interrupt handler. This function cannot be used in interrupt-prohibited states other than interrupt handlers.

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 notified 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 side 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 make certain that this function will succeed, make it loop until it succeeds as shown below. (This example does not take into account mistakes such as wrong arguments.)

> Example:
> `while( PM_GetAmpGain( ... ) != 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` (this function) and `PM_GetAmpGainLevel`. 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 is new; it has been added for the TWL system and can get 120 gain levels. See the `PM_GetAmpGainLevel` function.

## 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_SetAmpGain*`
`PM_GetAmpGainLevel*`

## Revision History

2008/08/23 Elaborated on `PM_RESULT_BUSY`.
2008/05/01 Added support for 120 amplifier gain levels.
2005/07/07 Added a reference to the `PM_RESULT_ERROR` return value.
2004/08/09 Initial version.

CONFIDENTIAL