Xiaomi Mi Watch 2021
Fit for scheduled disassembly.
They say time makes fools of us all, but that hasn’t stopped Xiaomi from working around the clock on a totally redesigned Mi Watch. Does its newest timepiece earn a place on your wrist? Tick tock, only this teardown can tell.
Major tech specs
• 1.39-inch (35mm) circular AMOLED display with 454x454 resolution
• 11.8mm thickness at 32g
• Wireless charging
• Accelerometer, gyro, heart rate, barometer, compass,
SpO2 (blood oxygen testing)
• Water-resistant to five atmospheres
• Bluetooth 5.0
Key findings
• We’re not seeing major changes in terms of hardware components over last year’s square Chinese version of the Mi Watch, but the new design direction is evident. This watch even grew another button, perhaps to keep up with Samsung. Maybe there are only so many ways to shape something that straps to your wrist. Let’s look inside….
• Even though it’s water-resistant up to 50 meters, this Mi Watch opens with a Torx T2 bit from our Mako Driver Kit and a little prying. It’s nice to be reminded that “waterproof” doesn’t have to mean “glued together.” Our first look inside is encouraging, too, as we spot some standard Phillips screws; though it would have been even better if only one screwdriver was needed.
• A bit of prying frees the battery. It’s great to see this common repair prioritized, with a modular connector, no soldering required. The battery is a 1.62Wh (420mAh at 3.85V) Li-ion block, which charges wirelessly. Xiaomi claims it can power the watch for 16 days, or 50 hours during sports. The bottom part of the watch case also bears a cable assembly with a tiny vibration motor, the heart rate and SpO2 sensor array, a barometric sensor, and a MEMS mic. Behind the sensor board is a Texas Instruments AFE44l30 biosensor analogue front end module.
• Just two Phillips screws secure the mainboard – twist them out, and the board floats free. After removing the mildly glued-in button cable, we find an Ambiq Micro AMA3B MCU and a Bosch Sensortec BMI270 three-axis accelerometer/gyroscope on the top side of the board, while the bottom side features an STMicro STM32L4R9ZI6P microcontroller, Paragon PN26Q01AWSIUG 1Gb NAND flash memory, a geomagnetic sensor (likely), electronic compass, and an SGMicro SGM41562 Li-ion battery charger with power path management.
• It’s been a pretty good experience so far, but here’s the part we’ve been avoiding. To free up the display assembly, we had to use a heat gun at about 300 C and a razor blade, causing the screen some damage. We also gave playing cards a try, only for the display layers to separate. Then the actual screen shattered in our hands. The last things to come off are the two side buttons, held in place by tiny metal washers on the inside.
• Repairability Score: 5 out of 10 (10 is easiest to repair). The opening procedure is simple and glueless. Connectors are modular and don’t overly overlap. The battery is easily accessible for repairs. Opening requires a somewhat uncommon T2 Torx driver, but Phillips screws grace the inside. Many components are grouped together and can’t be replaced individually. Display removal seems impractical and repairs will probably require replacing the watch casing.