wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 103

• Manufacturer Part Number: wm8400
• Description: Wolfson Audioplustm Hi-fi Audio Codec And Power Management Unit For Mobile Multimedia
• Manufacturer: Wolfson Microelectronics plc

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Pre-Production
Note:
Note that the GPI7 and GPI8 input pins can also be used as inputs to the Main Interrupt circuit on the
WM8400, configured in Registers R79 - R81, and signalled externally on the NIRQ pin. In this
configuration, the GPI7 and GPI8 inputs represent the Jack Detect Left and Jack Detect Right inputs
respectively. See “Interrupt Events” for details of this function.
MICBIAS CURRENT AND ACCESSORY DETECT
Current detection is provided on the microphone bias source MICBIAS. This can be configured to
detect when an external accessory (such as a microphone) has been connected. The output voltage
of the microphone bias source is selectable; two current detection threshold levels can be set.
The logic signals from the current detect circuits may be output directly on a GPIO pin, and may also
be used to generate CODEC Interrupt events. Configuration of the GPIO pins for accessory detect
output is described in Table 63 and Table 64 and also in the example settings below.
The accessory detection logic provides inputs to the CODEC Interrupt function, with selectable
enable and polarity control. The associated interrupt bits (MIC1_SHRT and MIC1_DET) are latched
once set and can be polled at any time or used as inputs to the CODEC IRQ output. The interrupt
bits are reset by writing a logic ‘1’ to the MIC1_SHRT and MIC1_DET register bits. See “CODEC
Interrupt Event Output” for more details of the CODEC Interrupt event handling.
If direct output of the MICBIAS current detect function is required to the external pins of the WM8400,
the following register settings are required:
When GPIOn_SEL = 1000 or 1001, the selected accessory detection status indication is output on
the GPIOn pin. A logic 1 indicates that the associated Jack Detect is asserted. Note that the polarity
is not programmable for GPIO output; the GPIO_POL register bits in Table 63 affect the Interrupt
behaviour only.
The register fields used to configure the MICBIAS Current Detect function are described in Table 65.
Note that the MICBIAS Current Detection function also provides input to the Main Interrupt circuit on
the WM8400, configured in Registers R79 - R81, and signalled externally on the NIRQ pin. See
“Interrupt Events” for details of this function.
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GPIO 1 is referenced to I2S1VDD
GPIOs 2to 6 are referenced to I2S2VDD
The GPIs 7 and 8 are referenced to AVDD
ALRCGPIO1 = 1 (only required if using GPIO1)
MCLK_SRC = 0 (only required if using GPIO2)
AIF_SEL = 0 (only required if using GPIO3, GPIO4 or GPIO5)
ALRCGPIO6 = 0 (only required if using GPIO6)
AIF_TRIS = 0
GPIOn_SEL = 1000 for the selected GPIO MICBIAS Current Detect output pin
GPIOn_SEL = 1001 for the selected GPIO MICBIAS Short Circuit Detect output pin
GPIOn_PU = 0 for the selected GPIO MICBIAS output pin or pins
GPIOn_PD = 0 for the selected GPIO MICBIAS output pin or pins
PP, April 2009, Rev 3.0
WM8400
103