About: MCU STOP Mode & MHU Multicore Demo

For Ensembe E1, E3, E4, E5, E6, E7 or E8

• RTSS-HE logs are on LP-UART (RX P9_1 and TX P9_2)
• RTSS-HP logs are on UART4 (RX P12_1 and TX P12_2)

For Ensemble E1C or Balletto B1

• RTSS-HE logs are on LP-UART (RX P2_0 and TX P7_1)

Changing the UART instance and pinmux is done via the retarget_config.h file.

    .
    ├── ...
    ├── device/
    │   ├── ensemble/
    │   |   ├── RTE/
    │   │   │   ├── Services/
    │   │   |   │   ├── AE1C1F4051920PH_M55_HE/retarget_config.h
    │   │   |   │   ├── AE722F80F55D5LS_M55_HE/retarget_config.h
    │   │   |   │   ├── AE722F80F55D5LS_M55_HP/retarget_config.h
    │   │   |   |   ├── AE822FA0E5597LS0_M55_HE/retarget_config.h
    │   │   |   |   └── AE822FA0E5597LS0_M55_HP/retarget_config.h
    │   │   │   └── ...
    │   │   └── ...
    │   └── ...
    └── ...

Refer to the sample ATOC data structure at the end of this README. The "deferred" flag instructs the Secure Enclave to skip booting a core during power-on.

At first power-on, only one core, the HE-M55, is booted by the Secure Enclave. The HE core detects that there are no pending wake events. It assumes that the MCU is being powered on for the first time and so it performs the first-time system setup. Those steps are to configure the aiPM Off Profile, initialize UART for application logging, configure the LPTIMER as its wakeup source, and finally it puts the MCU into global STOP Mode. The MCU stays in STOP Mode until the next LPTIMER expiration (configured for 1000 ms by default). Each LPTIMER expiration is a wake event that brings the MCU out of STOP Mode.

In response to the wake event, the HE-M55 core spends some time awake in a while(1) loop for 100 ms. This is just to demonstrate the HE core is awake and busy with some task. When the task is complete then the HE core returns the MCU to STOP Mode. Every tenth LPTIMER wake event the HE-M55 core uses the Message Handling Unit (MHU) to wake up the HP-M55 core. While waiting for a response from the HP core, the HE will enter deep sleep (subsystem stays on).

When the HP core receives a message via the MHU, it will run for some time in a while(1) loop before returning a response to the HE core. Again, this is just to demonstrate the HP core is awake and busy with some task. If the HP does not respond in time the HE core will timeout and reset it like a watchdog.

For Ensemble E1, E1C or Balletto B1, we will only need to build a binary for the RTSS-HE. MCU STOP Mode is demonstrated with only one core.

Building the binaries

Open the directory using VSCode and switch to the CMSIS View (CTRL+SHIFT+ALT+S). Click the gear icon labeled "Manage Solution Settings". Here you will choose the Active Target. If you are planning to run this demo on the Devkit-e7, then you will want to build binaries for the E7-HE and E7-HP. Otherwise, for the Devkit-e8, then build binaries for the E8-HE and E8-HP. Use this Manage Solution tab to switch between Target Types and use the hammer icon in the CMSIS View to build the application.

After the binaries are built, switch to the Explorer View (CTRL+SHIFT+E). The binaries will be located in the out directory, for example:

.
├── ...
├── out/
│   ├── app_he/
│   |   ├── E1C-HE/
│   |   |   ├── debug/app_he.bin
│   |   |   └── release/app_he.bin
│   |   ├── E7-HE/
│   |   |   ├── debug/app_he.bin
│   |   |   └── release/app_he.bin
│   |   └── E8-HE/
│   |       ├── debug/app_he.bin
│   |       └── release/app_he.bin
│   └── app_hp/
│       ├── E7-HP/
│       |   ├── debug/app_hp.bin
│       |   └── release/app_hp.bin
│       └── E8-HP/
│           ├── debug/app_hp.bin
│           └── release/app_hp.bin
└── ...

Debugging the binaries

• Switch to the Debug and Run view (CTRL+SHIFT+D) and press F5
• TIP: You may want to use SE tools integration to install the CPU stubs

Programming the binaries

Use the below json to configure your ATOC. Copy the binaries to the app-release-exec/build/images folder and proceed with the usual steps of generating the ATOC and writing to MRAM.

{
  "DEVICE": {
    "disabled" : false,
    "binary": "app-device-config-no-hfxo.json",
    "version" : "1.0.0",
    "signed": false
  },
  "HE_MRAM": {
    "disabled" : false,
    "binary": "M55_HE_img.bin",
    "mramAddress": "0x80000000",
    "version": "1.0.0",
    "cpu_id": "M55_HE",
    "flags": ["boot"],
    "signed": false
  },
  "HP_MRAM": {
    "disabled" : false,
    "binary": "M55_HP_img.bin",
    "mramAddress": "0x80200000",
    "version": "1.0.0",
    "cpu_id": "M55_HP",
    "flags": ["boot","deferred"],
    "signed": false
  }
}

Power Measurement on Alif DevKit

Refer to the power measurement points described in the aiPM Examples User Guide