Differences

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--- audio_amplifier [2025/01/06 22:57] – created arisotura
+++ audio_amplifier [2025/03/21 22:54] (current) – arisotura
@@ Line 4: / Line 4: @@
 No datasheet for it has been found, though there is a datasheet for the [[https://kuribo64.net/get.php?id=BHBmpgjQw1TpIgug|TLV320AIC3100]], which appears to be a close match.
+===== Clock generation =====
+The amplifier's input clock (MCLK) is sourced from [[General_registers|register 0xF000003C]].
+The amplifier's settings define the sample clock (WCLK) and bit clock (BCLK), which determine the audio sample rate.
+===== Registers =====
+A large amount of the audio amplifier's functionality seems to closely match the TLV320AIC3100. There are some minor differences.
+**Page 1 register 51**
+Stock firmware sets this register to values: 0x00, 0x40 or 0xC0.
+This register is 'reserved' in the documentation. Not known what it's for.
+===== Hardware differences =====
+The gamepad firmware reads the headset detect register (page 0 register 67) to determine which coefficient table to use for headphones.
+However, the headset detect functionality is misused: the value returned by the register actually depends on the motherboard revision.
+On revision 01, the amplifier's VOL/MICDET input is tied to ground. The headset detect register always reads as 0xA0.
+On revision 20, VOL/MICDET is tied to Vcc instead. The headset detect register always reads as 0x80.
+The headset detect register is thus used to identify the motherboard revision, probably to account for differences in audio circuitry.
+Actual headset detection is done by the [[UIC]].