Power Control & Status¶
Status Indication¶
LattePanda Mu x86 compute module provides two status output pins, PSON and SLP_S4, to indicate the current system power state (e.g., S0, S3). These pins can be used to control the power enable lines for carrier board peripherals or to drive status LEDs.
Pin Definition¶
| Pin Name | Pin Number | Note |
|---|---|---|
| PSON | 5 | Output HIGH only when S0(Working) |
| SLP_S4 | 7 | Output HIGH only when S0(Working) and S3(Sleeping) |
💡 Due to the limited drive capability of the PSON and SLP_S4 pins, an external NMOS is required to drive an LED indicator.
Status Logic Table¶
| System State | PSON Level | SLP_S4 Level | Note |
|---|---|---|---|
| Working (S0) | HIGH | HIGH | System running normally |
| Sleep (S3) | LOW | HIGH | Suspend to RAM |
| Hibernate (S4) | LOW | LOW | Suspend to Disk |
| Shutdown (S5) | LOW | LOW | Soft OFF |
| Standby (G3) | LOW | LOW | Powered but not Turned ON |
Power Control¶
LattePanda Mu x86 compute module provides signal lines for power and reset buttons, which function exactly like those on a standard laptop or desktop computer.
Pin Definition¶
| Pin Name | Pin Number | Note |
|---|---|---|
| PWR_SW# | 1 | System Power Switch; Internally 10K Pulled Up |
| RST_SW# | 3 | System Reset Switch; Internally 10K Pulled Up |
PWR_SW#¶
- Connect to a physical power button. Active Low.
- A low pulse duration of ≥ 125ms is recommended for reliable detection.
- Holding Low for > 4 seconds will trigger a forced shutdown.
RST_SW#¶
- Connect to a physical hard reset button. Active Low.
- A low pulse duration of ≥ 16ms is recommended to ensure a successful reset.
ESD Protection¶
Since buttons are frequently touched, they are vulnerable to electrostatic discharge (ESD). Adding ESD protection diodes is strongly recommended.
- Reverse Working Voltage: 5V
FAQ¶
| Question | Potential Cause / Check Point | Explanation / Solution |
|---|---|---|
| CMOS Error appears after boot | Low RTC battery voltage | Replace the RTC battery with a new one. |
| First initialization after BIOS update | This is normal behavior. The message will disappear once initialization is complete. | |
| Boot process is extremely slow every time | PWR_SW# pin held low (>10s) before booting | If the PWR_SW# is held for over 10s, it triggers a BIOS Reset. The subsequent boot requires full hardware re-initialization, causing a significant delay. |