Normal I2C
Address: 0x1A
https://statics.cirrus.com/pubs/proDatasheet/WM8962_Rev4.4.pdf
The I2C address seems to be 0x34 but that's the 8 Bit address. Shift the address 1 to the right (>>1) and you get 0x1A as 7Bit address
Wolfson WM7220 Microphones
PMIC or Power Managment IC (PMIC) is an IC that contains a lot of regulators which power the CPU, Sensors and other components of Surface RT
400 kHz
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- 0a -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- 1a -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- 2d -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- 4a -- 4c -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: 60 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- Access to I2C Bus 4 is not known right now.
Normal I2c
Address: 0x0A
Surface RT uses the Embedded Controller Topology. The controller is located at 0xa.
That means that there must be an IC somewhere which interacts with the Charger and the Fuelgauge and provide an interface to both of them to the SoC.
The Charger and the Fuelgauge are exposed through 0xa which provides an ACPI interface.
The ACPI BAT0 device deals with the Fuelgauge.
The ACPI ADP0 device deals with the Charger.
The ACPI methods like _BIX, _BTS, ... provide all the necessary information about the battery and the charger.
They can be decrypted by reading the ACPI Spec p. 492 10.2 Control Method Batteries
https://wiki.ubuntu.com/Kernel/Reference/Battery "(Control Method) Batteries and ACPI are tied together in quite a complex way. Generally, the battery state information is transmitted over a SMBUS bus to the embedded controller, a.k.a. EC, which in turn interfaces to the OS via ACPI methods. These methods can interrogate the embedded controller for battery state information ..."
Battery <-- EC <--> BIOS ACPI Methods <--> OS
Since there is no ACPI implementation for ARM32 and we need to replace the ACPI Methods with a custom driver. all Necessary information can be found in the SSDT0000 ACPI table
The Embedded Controller directly interacts with the Charger and the Fuelgauge.
BQ28400
https://www.ti.com/lit/ug/sluu431/sluu431.pdf https://www.ti.com/lit/ds/symlink/bq28400.pdf?ts=1625607689401&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ28400
BQ24725A
The Embedded Controller topology prevents the use of SmartBatterySystem (SBS) and requires an ACPI or custom driver. ACPI isn't (fully) implemented on ARM32 therefore we need a custom driver which resembels the ACPI methods.
https://uefi.org/sites/default/files/resources/ACPI_5_0_Errata_B.pdf
SMBus SBS
Address: 0x4C
https://www.onsemi.com/pdf/datasheet/nct1008-d.pdf
The Slave address and the ManufacturerID register do match. + This sensor is also found on Cardhu.
