GPIO Debugging

When using GPIO debugging, users need to go to menuconfig, and enable CONFIG_PM_TRACE. If enabled, some GPIOs will be used to signal events such as RTOS ticks, frequency switching, entry/exit from idle state. For a list of GPIOs, see pm_trace.c file. This feature is intended to be used when analysing/debugging behavior of power management implementation and should be kept disabled after the debugging.

The relevant GPIOs are shown below, with two GPIOs for each event, corresponding to CPU0 and CPU1. Since ESP32-C3 is a single-core chip, only the first column of GPIOs is effective when debugging. During development, users can also modify the GPIO used by modifying the source code. Before debugging, connect the selected GPIO to an instrument such as a logic analyser or oscilloscope.

/*GPIOs to use for tracing of esp_pm events.
* Two entries in the array for each type, one for each CPU.
* Feel free to change when debugging.
static const int DRAM_ATTR s_trace_io[] = {
    BIT(4),  BIT(5),        //ESP_PM_TRACE_IDLE
    BIT(16), BIT(17),       //ESP_PM_TRACE_TICK
    BIT(18), BIT(18),       //ESP_PM_TRACE_FREQ_SWITCH
    BIT(25), BIT(26),       //ESP_PM_TRACE_ISR_HOOK
    BIT(27), BIT(27),       //ESP_PM_TRACE_SLEEP
    BIT(2),  BIT(3),        //ESP_PM_TRACE_IDLE
    BIT(4),  BIT(5),        //ESP_PM_TRACE_TICK
    BIT(6),  BIT(6),        //ESP_PM_TRACE_FREQ_SWITCH
    BIT(8),  BIT(9),        //ESP_PM_TRACE_ISR_HOOK
    BIT(18), BIT(18),       //ESP_PM_TRACE_SLEEP

To enable CONFIG_PM_PROFILING, users need to run the menuconfig command to start the configuration tool, go to Component config → Power Management, and enable Enable debug tracing of PM using GPIOs. The screenshot of how to Enable debug tracing of PM using GPIOs for ESP32-C3 is shown in Figure 12.6.

Figure 12.6. ESP32-C3 low-power GPIO debug configuration

The debugging can begin after completing the above-mentioned configuration. By observing different GPIO states, users get to know the current state of the CPU and the corresponding power mode, and further understand which power modes consume more power and can be optimised. Figure 12.7 shows the waveform of ESP32-C3's GPIO debugging for reduced power consumption. The upper section shows the real-time power consumption of ESP32-C3, and the lower section shows the GPIO waveform corresponding to ESP_PM_TRACE_SLEEP event.

Figure 12.7. ESP32-C3 low-power GPIO debug waveform