Ec specification

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Operational Specification of the XO embedded controller (EC)

These pages will eventually document the commands and responsibilities of the embedded controller (EC) in the XO system. an example of an embedded controller is like one in a washing machine Currently its not much more than a cut and paste from a variety of emails, trac tickets, and operational info extracted from the way the EC is known to work. Some of the descriptions are a bit odd and terse as the source is from non-native English speakers. More verbosity and better descriptions will be added as time allows.


EC Port 6c Command List

These commands are issued using a simple protocol - See Revised EC Port 6C Command Protocol.

  • 0x03 SPI write protect
  • 0x08 Get Firmware revision byte
  • 0x10 Read voltage (2 bytes)
  • 0x11 Read current (2 bytes)
  • 0x12 Read ACR (2 bytes)
  • 0x13 Read battery temperature (2 bytes)
  • 0x14 Read ambient temperature (2 bytes)
  • 0x15 Read battery status (1 byte)
    • Bit 0: 1: battery exists
    • Bit 1: 1: battery full charged
    • Bit 2: 1: battery low
    • Bit 3: 1: battery error
    • Bit 4: 1: AC in
    • Bit 5: 1: battery charging
    • Bit 6: 1: battery discharging
    • Bit 7: 1: battery trickle charging
  • 0x16 Read Battery State of Charge (SOC) (1 byte)
  • 0x17 Read Battery gas gauge chip serial number (6 bytes)
  • 0x18 Read Battery gas gauge EEPROM databyte
    • Cmd data is the EEPROM address of the byte requested
    • Result is 1 byte of EEPROM data
  • 0x19 Read board id (1 byte)
  • 0x1a Read SCI source (1 byte)
    • 0x01 Game button
    • 0x02 Battery Status Change. Generated for any of:
      • AC plugged/unplugged
      • Battery inserted/removed
      • Battery Low
      • Battery full
      • Battery error
    • 0x04 Battery SOC Change
    • 0x08 Battery subsystem error
    • 0x10 Ebook mode change
    • 0x20 Wake up from Wlan
    • 0x40 AC power plug/unplug
  • 0x1b Write SCI mask (1 byte)
  • 0x1c Read SCI mask (1 byte)
  • 0x1d Game key status (2 bytes) 9 bits of key status. 1 indicates key is depressed.
    • Bit 1: KEY_LR_R
    • Bit 2: KEY_RT_R
    • Bit 3: KEY_UP_L
    • Bit 4: KEY_DN_L
    • Bit 5: KEY_LF_L
    • Bit 6: KEY_RT_L
    • Bit 7: KEY_COLOR/MONO
    • Bit 8: KEY_UP_R
    • Bit 9: KEY_DN_R
  • 0x1e Set date (day/mon/year)
    • Need details for using this.
  • 0x1f Read battery subsystem error code (1 byte)
    • 0x02 Pack info fail (LiFePO4 & NiMH)
    • 0x04 Over voltage checking fail (LiFePO4)
    • 0x05 Over temperature (58C) (LiFePO4)
    • 0x06 Gauge stop or sensor break (LiFePO4 & NiMH)
    • 0x07 Sensor out of control (NiMH)
    • 0x09 Battery ID fail & temperature > 52C
    • 0x10 ACR fail (NiMH)
  • 0x20 Init NiMH Battery
  • 0x21 Init LiFePO4 Battery
  • 0x22 Init Goldpeak LiFePO4 Battery
  • 0x23 Set WLAN Power on/off - DEPRECATED!
  • 0x24 Wake up WLAN
  • 0x25 WLAN reset (leaving WLAN on)
  • 0x26 DCON power enable/disable
    • Write a 0 to disable
    • Write a 1 to enable
  • 0x2a Read EBOOK mode
    • Bit 0 EBOOK sensor status
  • 0x2b Read power rail status
    • Bit 0 WLAN status
    • Bit 1 DCON status
  • 0x2c Read battery type
    • 1st Nibble (Bits 0-3)
      • 0001 NiMH
      • 0010 LiFePo4
    • 2nd Nibble (Bits 4- 7)
      • 0001 Goldpeak
      • 0010 BYD
  • 0x2e Read Ambient temp raw
  • 0x2f Wakeup keyboard (Future: not-implemented)
  • 0x30 Read lid switch (Future: not-implemented)
  • 0x31 Read 1-wire interface type
  • 0x32 Set SCI inhibit
    • This command must be issued prior to turning off the CPU core voltage
  • 0x33 Enable AutoWak
  • 0x34 Clear SCI inhibt
    • If a suspend fails and MAIN_ON never goes low this command will clear the SCI inhibit.
  • 0x35 WLAN off
    • Asserts the hardware reset line of the WLAN device. Use command 0x25 to de-assert.
  • 0x84 Read SCI queue
    • 0x0 Empty sci
    • 0x01 Key press
    • 0x02 Battery
    • 0x04 Battery state change
    • 0x08 Batter error
    • 0x10 Ebook
    • 0x20 Wlan packet
    • 0x40 AC power

EC IO Pinout

Model C1

  • Pin 1: GPIOE0 EC_WP#
  • Pin 2: GPIOE1 CV_SET
  • Pin 3: GPIOE2 DQ
  • Pin 4: GPIOE3 LED_CHG_G#
  • Pin 6: GPIO00 VR_ON#
  • Pin 9: GPIO01 WLAN_EN
  • Pin 10: GPIO02 SWI#
  • Pin 23: GPIO06 TX
  • Pin 24: GPIO07 RX/BAT_L0
  • Pin 25: GPIO08 ACIN
  • Pin 26: GPIO09 LED_PWR#
  • Pin 27: GPIO0A LED_CHG_R#
  • Pin 28: GPIO0B WAKEUP
  • Pin 29: GPIO0C PWR_BUT#
  • Pin 30: ECRST#
  • Pin 31: GPIO0E CHG
  • Pin 32: GPIO0F CC0
  • Pin 33: GPIOE8 BAT_L1
  • Pin 34: GPIAD3 SUS_ON
  • Pin 35: GPIAD4 CVM
  • Pin 36: GPIAD5 WAKEUP_EC
  • Pin 37: GPIO10 EC->WLAN Wakeup
    • Fix schematic!!
  • Pin 38: GPIAD0 TEMP
  • Pin 39: GPIAD1 EC_ID
  • Pin 40: NC.
  • Pin 43: KBCLK
  • Pin 44: KBDAT
  • Pin 45: TPCLK
  • Pin 46: TPDAT
  • Pin 47: KEY_OUT_3/ISP_CLK
  • Pin 48: KEY_OUT_1/ISP_EN#
  • Pin 49: SPIWP#
  • Pin 50: POWER_BUTTON#
  • Pin 51: WLAN_RESET#
  • Pin 52: ECPWRRQST
  • Pin 53: KEY_OUT_2
  • Pin 54: WAKE_PRECHG
  • Pin 55: EB_MODE
  • Pin 56: MAIN_ON
  • Pin 57: PWR_BUT_IN

B1 < Model < C1

Not yet complete.

  • Pin 6: GPIO00 VR_ON#
  • Pin 9: GPIO01 WLAN_EN
  • Pin 10: GPIO02 SWI#
  • Pin 23: GPIO06 TX
  • Pin 24: GPIO07 RX/BAT_L0
  • Pin 25: GPIO08 EC_EAPD
  • Pin 26: GPIO09 LED_PWR#
  • Pin 27: GPIO0A LED_CHG_R#
  • Pin 28: GPIO0B WAKEUP
  • Pin 29: GPIO0C PWR_BUT#
  • Pin 31: GPIO0E CHG
  • Pin 32: GPIO0F CC0
  • Pin 37: GPIO10 EC->WLAN Wakeup
    • Fix schematic!!
  • Pin 1: GPIOE0 EC_WP#
  • Pin 2: GPIOE1 CV_SET
  • Pin 3: GPIOE2 DQ
  • Pin 4: GPIOE3 LED_CHG_G
  • Pin 33: GPIOE8 BAT_L1
  • Pin 39: GPIAD1 EC_ID

Board ID Values

The EC is responsible for determining the motherboard ID of a laptop. At the circuit level, this is specified by the ratio of the values of two resistors (R535 and R534), providing a voltage on the EC_ID signal input to the EC. Known combinations include:

VoltageEC ValueBoard IDComments
000-07hB3
08-17hguard band
1/8 * 3.3V18-27hB4
28-37hguard band
1/4 * 3.3V38-47hC1
48-57hguard band
3/8 * 3.3V58-67hC2
68-77hguard band
1/2 * 3.3V78-87hB2
88-97hguard band
5/8 * 3.3V98-A7hC3
A8-B7hguard band
3/4 * 3.3VB8-C7hF1
C8-D7hguard band
7/8 * 3.3VD8-E7hF2
E8-F7hguard band
3.3VF8-FFhF3

The F[123] values are place holders in the EC code which prevents EC from bricking a machine that has had the resistors changed because it has to fall back on a B1 layout. B1 IO layout detection fails to work correctly so its the default.

KeyCodes for Buttons

Key matrix Make code Break code
Bit 9: KEY_DN_R, {0xE0,0x66,0x00} {0xE0,0xE6,0x00}
Bit 8: KEY_UP_R, {0xE0,0x65,0x00} {0xE0,0xE5,0x00}
Bit 7: ROTATE {0x69,0x00,0x00} {0xE9,0x00,0x00}
Bit 6: KEY_RT_L, {0x68,0x00,0x00} {0xE8,0x00,0x00}
Bit 5: KEY_LF_L, {0x67,0x00,0x00} {0xE7,0x00,0x00}
Bit 4:KEY_DN_L, {0x66,0x00,0x00} {0xE6,0x00,0x00}
Bit 3: KEY_UP_L, {0x65,0x00,0x00} {0xE5,0x00,0x00}
Bit 2: KEY_RT_R, {0xE0,0x68,0x00} {0xE0,0xE8,0x00}
Bit 1:KEY_LF_R {0xE0,0x67,0x00} {0xE0,0xE7,0x00}

Firmware Address Map

0x00000 - 0ffff EC
0x10000 - dffff OFW
0xe0000 - ef7ff Reserved
0xef800 - effff Manufacturing data
0xf0000 - fffff Early startup code

Port 66 Commands

There are also some EC commands that use ports 0x66 and 0x62. Some of these are standard ACPI commands as defined in the external ACPI spec, others are custom.

The port 66 protocol is essentially the standard ACPI EC interface protocol.

1. Wait for port66.IBF = 0

2. Write command byte to port 66.

3. For each outgoing data or address byte:

3a. Wait for port66.IBF = 0

3b. Write data or address byte to port 62.

4. For each incoming data byte:

4a. Wait for port66.OBF = 1

4b. Read data byte from port 62.

5. If the command requires no data or address bytes, you can determine when the command was accepted/executed by waiting for port66.IBF=0.

ACPI-defined port 66 commands

  • 0x80 Read EC (write 0x80 to port 66, write address byte to port 62, read data byte from port 62)
  • 0x81 Write EC (write 0x81 to port 66, write address byte to port 62, write data byte to port 62)
  • 0x82 Burst Enable (write 0x82 to port 66, read data byte from port 62 - the data byte is "burst ACK", value 0x90)
  • 0x83 Burst Disable (write 0x83 to port 66, wait for port66.IBF=0)
  • 0x84 Query EC (i.e. read SCI event queue) (write 0x84 to port 66, read data byte from port 62). When the data byte is 0, it means that the SCI event queue is empty.

OLPC-specific port 66 commands

  • 0xd5 Power Off (write 0xd5 to port 66)
  • 0xd7 Host Power Cycle
  • 0xd8 Keyboard stop (write 0xd8 to port 66) Useful when updating EC microcode in SPI FLASH (Sets GPIOE0 - EC_WP# - to low, and sets EC state to PRE_RESET). I think the GPIOE0 thing doesn't happen until the 8051 is later reawakened via the 0xff14 register.
  • 0xdd Keyboard pause (write 0xdd to port 66) Useful when updating manufacturing data. What this does is put the 8051 into IDLE mode so that it is not fetching instructions from SPI FLASH. It also disables the watchdog timer. However, the 8051 is configured (via the register at 0xff0c) to come out of IDLE mode when an interrupt occurs. This has the good effect that it is possible to issue the 0xdf command to resume activity (because the port 66 IBF event will wake up the 8051), but the bad effect that other interrupts, such as keyboard activity, will also wake it up. The problem with keyboard wakeup is that it could happen during the process of writing to SPI FLASH and thus corrupt the FLASH. The solution might be to mask off some interrupts so only the port66 one is enabled during this mode.
  • 0xdf Keyboard resume (write 0xdf to port 66) Useful when updating manufacturing data

Indexed access to EC internal locations

You can access some internal locations inside the EC with an index/data protocol. The "address" is a 16-bit number.

Write address.hi_byte to port 0x381, write address.lo_byte to port 0x382, and read or write the data byte at port 0x383.

For successive accesses to the same or nearby addresses, you don't have to rewrite address bytes that don't change.

This feature is disabled when the laptop is in secure mode (WP tag set), since it is a security hole. But indexed I/O will probably continue to be used for updating the SPI FLASH contents, since that has to be done when the 8051 is not running. SPI FLASH updating will be done in a secure firmware mode that happens before the user has the ability to get interactive control.

Revised Protocol

Revised EC Port 6C Command Protocol

Register Settings

EC Register Settings

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