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Netronix MSP430 embedded controller
In older board designs, such as the Kobo Aura (N514/E606F0B), Netronix uses a MSP430 as an embedded controller (EC) which handles several features including basic power sequencing of the i.MX SoC. The MSP430 is connected via I²C and responds to address 0x43.
There are two register layouts. The new one is detected by the NEWMSP macro,
which checks if the version number is 0xe916. This file documents the old
layout.
Interrupts are signaled through a GPIO line in falling edge mode.
For a register read:
- write one byte, the register address
- read two bytes (treated as a big-endian u16 in the original driver)
For a register write:
- write one byte, the register address
- write two bytes, the register value (also a BE u16 in the original driver)
Even though the driver treats all register accesses as 16 bits wide, only the upper (first) byte is used in many cases. This is the case when this file speaks of 8-bit registers or values.
When read as a big-endian u16, this register provides the version number of the
EC. A value of 0xe916 indicates the new register layout, which is not
described in this document.
The time is set by writing 8-bit values into the high bytes of the following registers:
| Register | Description |
|---|---|
| 0x10 | year, zero means 2000 |
| 0x11 | month, one-based |
| 0x12 | day of the month, one-based |
| 0x13 | hour, zero-based |
| 0x14 | minute, zero-based |
| 0x15 | second, zero-based |
| Register | Type | Description |
|---|---|---|
| 0x16 | u8 | hour |
| 0x17 | u8 | minute |
| 0x18 | u8 | set to 0x01 in msp430_auto_power |
| Register | Type | Description |
|---|---|---|
| 0x1b | u8 | alarm offset in seconds, high byte |
| 0x1c | u8 | alarm offset in seconds, low byte |
| Register | High byte | Low byte |
|---|---|---|
| 0x20 | year; zero means 2000 | month, one-based |
| 0x21 | day of the month, one-based | hour, zero-based |
| 0x23 | minute, zero-based | second, zero-based |
- 0xff: "Jospeh 100108 // start ADC"
This 16-bit register contains the battery voltage, in the range 0-1023.
TODO: provide conversion formula
This 16-bit register contains different bits that indicate which interrupts have occurred. It can be read and written.
| Bit value | description |
|---|---|
| 0x0001 | Battery is critically low |
| 0x0002 | only used in dead code |
| 0x0008 | On board E606F0B (Kobo Aura), this bit indicates that the battery is charging (or discharging?) |
| 0x8000 | Alarm triggered |
- Write the 8-bit value 0x08 to keep the board powered on, or 0x00 to not keep it powered on.
- On E60632, 0x10 is written to this register, in
msp_poweroff.
- Write the 8-bit value 0xff to reset the board.
| Register | Type | Description |
|---|---|---|
| 0xa1 | u8 | set to 0xff when disabling auto-poweroff |
| 0xa2 | u8 | set to 0xff when disabling auto-poweroff |
| 0xa3 | u8 | 0x01: enable PWM, 0x00: disable PWM |
| 0xa4 | u8 | cycle time (8MHz/frequency), low byte |
| 0xa5 | u8 | cycle time (8MHz/frequency), high byte |
| 0xa6 | u8 | duty cycle, low byte |
| 0xa7 | u8 | duty cycle, high byte |