# Source: codec_zero.adoc

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=== Raspberry Pi Codec Zero

Raspberry Pi Codec Zero is a Raspberry Pi Zero-sized audio HAT. It delivers bi-directional digital audio signals (I2S) between a Raspberry Pi and the Codec Zero's on-board Dialog Semiconductor DA7212 codec. The Codec Zero supports a range of input and output devices.

* High performance 24-bit audio codec
* Supports common audio sample rates between 8-96 kHz
* Built in micro-electro-mechanical (MEMS) microphone (Mic2)
* Mono electret microphone (Mic2 left)
* Automatic MEMS disabling on Mic2 insert detect
* Supports additional (no fit) mono electret microphone (Mic1 right)
* Stereo auxiliary input channel (AUX IN) - PHONO/RCA connectors
* Stereo auxiliary output channel (Headphone/AUX OUT)
* Flexible analogue and digital mixing paths
* Digital signal processors (DSP) for automatic level control (ALC)
* Five-band EQ
* Mono line-out/mini speaker driver: 1.2 W at 5 V, THD < 10%, R = 8 Ω

image::images/Codec_Zero_Board_Diagram.jpg[width="80%"]

The Codec Zero includes an EEPROM which can be used for auto-configuration of the Linux environment if necessary. It has an integrated MEMS microphone, and can be used with stereo microphone input via a 3.5 mm socket and a mono speaker (1.2W/8Ω).

In addition to the green (GPIO23) and red (GPIO24) LEDs, a tactile programmable button (GPIO27) is also provided.

==== Pinouts

[cols="1,12"]
|===
| *P1/2* | Support external PHONO/RCA sockets if needed. P1: AUX IN, P2: AUX OUT.
| *P1* | Pin 1 is square.
|===
image::images/CODEC_ZERO_ZOOMED_IN_DIAGRAM.jpg[width="50%"]

Codec Zero is an ideal design starting point for small-scale projects such as walkie-talkies, smart doorbells, vintage radio hacks, or smart speakers.