Concepts First

• MTimer (machine timer): the system-level "heartbeat" providing periodic interrupts, microsecond timestamps, and delays — the timing base of every example.
• Tick: each timer trigger is a tick; the example prints tick:N once per second.
• MTimer vs TIMER: MTimer is the system machine timer; TIMER is the general-purpose timer (multi-channel compare/capture), see TIMER.

Example Overview

This page is based on the mtimer example in the official Bouffalo SDK (examples/peripherals/mtimer), which demonstrates the machine timer (MTimer) interrupt period:

• bflb_mtimer_config(1000000, systick_isr) sets the period to 1,000,000 microseconds (1 second) and registers the callback;
• The timer fires every second; the callback increments a counter and prints tick:N;
• MTimer is the system-level timer used as the time base for OS ticks, delays, and performance stats.

Operation Steps

1

Enter the Example Directory

No external wiring is needed for this page. Open a terminal and enter the MTimer example directory (prerequisite: set up the environment as in Quick Start (Linux) or Windows):

cd examples/peripherals/mtimer

2

Build the Project

Run the build command. The Ai-M62 (BL616) and Ai-M61 (BL618) belong to the same series, so both use bl616:

make CHIP=bl616 BOARD=bl616dk

3

Flash the Firmware

Connect the board with a USB cable, hold the BOOT button (IO2 on the Ai-M61-32S-Kit), briefly press EN/RST to enter download mode, then flash (replace the serial port with the one on your computer):

make flash CHIP=bl616 COMX=/dev/ttyUSB0

4

Run and Verify

Open a serial tool (baud rate 2000000). The example configures the MTimer period to 1 second; the ISR prints one line per trigger: tick:1, tick:2, … incrementing every second.

Code Execution Flow

The complete execution flow from startup to running is shown below (loop arrows mean repeated execution):

APIs Used by the Example

bflb_mtimer_config(period_us, isr)

Configures the machine timer period and registers the ISR. The period is in microseconds; 1000000 = 1 second.

Parameters:

• period_us: period in microseconds
• isr: callback, e.g. void isr(void)

Return: 0 on success; negative error code on failure

Other capabilities

MTimer also provides bflb_mtimer_delay_ms (millisecond delay) and bflb_mtimer_get_time_us (microsecond timestamp), used by many examples; this example only demonstrates the periodic interrupt.

Complete Code

The complete source below matches the effect described on this page. It is based on the official example (examples/peripherals/mtimer); the LED pins are adapted to the Ai-M61/62-32S-Kit onboard RGB LED. Collapsed by default, click to expand:

📜 Click to expand mtimer/main.c full code

#include "bflb_mtimer.h"
#include "board.h"

void systick_isr()
{
    static uint32_t tick = 0;
    tick++;
    printf("tick:%d\r\n", tick);
}

int main(void)
{
    board_init();
    bflb_mtimer_config(1000000, systick_isr);
    while (1) {
    }
}

FAQ

The tick interval is not 1 second

bflb_mtimer_config takes microseconds; change 1000000 to adjust the period. If the rate is odd, check that other code is not frequently disabling global interrupts.

Can I do heavy work in the ISR?

The callback runs in interrupt context and should stay short (the example only counts and prints); move heavy work to the main loop or a task using a flag.

MTimer vs TIMER?

MTimer is the system machine timer (periodic interrupt/timestamp); TIMER is the general-purpose timer with multiple compare/capture channels (see TIMER).

Have questions?

For any other questions, visit the unified Q&A and discussion board: Ai-Thinker Discussions