How to set accelleration range on BMI270 on AtomS3R (C126)? #228
Description
https://m5stack.lang-ship.com/catalog/products/controller/c126_atoms3r/ links to https://m5stack.oss-cn-shenzhen.aliyuncs.com/resource/docs/datasheet/core/K128%20CoreS3/BMI270.PDF, which contains this table on page 109
I imagine that the acceleration range, and other IMU parameters are configurable from M5Unified.
I'm trying to change the acceleration range from 8g to 16g, using the program included below.
However, I see something surprising when testing the device by holding it in my hand,
with the USB-C cable connected, and shaking the device, first gently, then rather hard.
The maximum acceleration appears clamped at 8g.
I'm using https://github.com/m5stack/M5Unified/releases/tag/0.2.13.
Could this be due to some hard-coding of that value, e.g., in
M5Unified/src/utility/imu/IMU_Base.hpp
Line 56 in 80922a5
This is code:
/**
* @file accel_range.ino
* @brief Test to verify ±16g accelerometer range configuration
*
* Test procedure:
* 1. Upload this sketch
* 2. Open serial monitor (115200 baud)
* 3. With the USB-C cable connected, shake sensor strongly by hand
* 4. Check if accel values exceed ±8g
*
* Expected result:
* - If ±16g works: values may exceed ±8g during strong shaking
* - If clamped to ±8g (default): values will never exceed ±8g
*/
#include <M5Unified.h>
// BMI270 I2C configuration
// BMI270 I2C address from M5Unified:
// https://raw.githubusercontent.com/m5stack/M5Unified/4a1c5343330f7d54cfab38302ebf98dc9ef6de0f/src/utility/imu/BMI270_Class.hpp
static const uint8_t BMI270_ADDR = 0x68;
static const uint32_t I2C_FREQ = 400000;
static const uint8_t ACC_RANGE_REG = 0x41;
void setup() {
auto cfg = M5.config();
cfg.serial_baudrate = 115200;
M5.begin(cfg);
Serial.println("=== BMI270 ±16g Range Test ===");
// Re-initialize I2C
M5.In_I2C.begin((i2c_port_t)I2C_NUM_0, 45, 0);
delay(100);
M5.Imu.update();
delay(100);
// Configure BMI270 to ±16g range
Serial.println("Configuring BMI270 ACC_RANGE to ±16g...");
if (!M5.In_I2C.writeRegister8(BMI270_ADDR, ACC_RANGE_REG, 0x03, I2C_FREQ)) {
Serial.println("ERROR: Failed to write ACC_RANGE");
} else {
Serial.println("Configuration complete: ±16g accel range");
}
Serial.println();
Serial.println("SHAKE THE SENSOR STRONGLY!");
Serial.println("Looking for accel values > ±8g...");
Serial.println();
Serial.println("Format: accel_raw(x,y,z) | accel_cal(x,y,z) g");
Serial.println("---");
// Disable M5Unified calibration to get raw readings
M5.Imu.setCalibration(0, 0, 0);
}
void loop() {
static uint32_t lastPrint = 0;
static float maxAbsAccel = 0;
uint32_t now = millis();
// Update sensor
if (M5.Imu.update()) {
// Get data
auto data = M5.Imu.getImuData();
int16_t raw_x = M5.Imu.getRawData(0);
int16_t raw_y = M5.Imu.getRawData(1);
int16_t raw_z = M5.Imu.getRawData(2);
float ax = data.accel.x;
float ay = data.accel.y;
float az = data.accel.z;
// Track maximum
float absMax = max(abs(ax), max(abs(ay), abs(az)));
if (absMax > maxAbsAccel) {
maxAbsAccel = absMax;
}
// Print at 10Hz
if (now - lastPrint >= 100) {
Serial.printf("raw:(%6d,%6d,%6d) | cal:(%7.3f,%7.3f,%7.3f) g | max: %.3f g",
raw_x, raw_y, raw_z,
ax, ay, az,
maxAbsAccel);
// Flag if we exceeded 8g
if (absMax > 8.0f) {
Serial.print(" *** EXCEEDED 8g! ±16g WORKS! ***");
}
Serial.println();
lastPrint = now;
}
}
delay(1);
}
Serial output:
01:42:33.725 -> === BMI270 ±16g Range Test ===
01:42:33.725 ->
01:42:33.725 -> Configuring BMI270 ACC_RANGE to ±16g...
01:42:33.725 -> Configuration complete: ±16g accel range
01:42:33.725 ->
01:42:33.725 -> SHAKE THE SENSOR STRONGLY!
01:42:33.725 -> Looking for accel values > ±8g...
01:42:33.725 ->
01:42:33.725 -> Format: accel_raw(x,y,z) | accel_cal(x,y,z) g
01:42:33.725 -> ---
01:42:33.725 -> raw:( -3323, 1558, 938) | cal:( 0.380, 0.811, 0.229) g | max: 0.811 g
01:42:33.768 -> raw:( -1244, 770, 603) | cal:( 0.188, 0.304, 0.147) g | max: 0.860 g
01:42:33.846 -> raw:( -965, 876, 1139) | cal:( 0.214, 0.236, 0.278) g | max: 0.860 g
01:42:33.942 -> raw:( -673, 1153, 1818) | cal:( 0.281, 0.164, 0.444) g | max: 0.860 g
01:42:34.040 -> raw:( -535, 1310, 1640) | cal:( 0.320, 0.131, 0.400) g | max: 0.860 g
01:42:34.135 -> raw:( -328, 1114, 1801) | cal:( 0.272, 0.080, 0.440) g | max: 0.860 g
01:42:34.272 -> raw:( -738, 749, 1998) | cal:( 0.183, 0.180, 0.488) g | max: 0.860 g
01:42:34.362 -> raw:( -729, 763, 1724) | cal:( 0.186, 0.178, 0.421) g | max: 0.860 g
01:42:34.459 -> raw:( -634, 767, 1728) | cal:( 0.187, 0.155, 0.422) g | max: 0.860 g
01:42:34.556 -> raw:( -434, 989, 1770) | cal:( 0.241, 0.106, 0.432) g | max: 0.860 g
01:42:34.653 -> raw:( -296, 1127, 1865) | cal:( 0.275, 0.072, 0.455) g | max: 0.860 g
01:42:34.653 -> raw:( -296, 1127, 1865) | cal:( 0.275, 0.072, 0.455) g | max: 0.860 g
01:42:34.782 -> raw:( -333, 844, 1858) | cal:( 0.206, 0.081, 0.454) g | max: 0.860 g
01:42:34.881 -> raw:( -492, 898, 2092) | cal:( 0.219, 0.120, 0.511) g | max: 0.860 g
01:42:34.976 -> raw:( -798, 492, 2012) | cal:( 0.120, 0.195, 0.491) g | max: 0.860 g
01:42:35.074 -> raw:( -833, 643, 1810) | cal:( 0.157, 0.203, 0.442) g | max: 0.860 g
01:42:35.170 -> raw:( -1106, 817, 1215) | cal:( 0.199, 0.270, 0.297) g | max: 0.860 g
01:42:35.268 -> raw:( -1638, 607, 805) | cal:( 0.148, 0.400, 0.197) g | max: 0.860 g
01:42:35.397 -> raw:( -1389, 1206, 631) | cal:( 0.294, 0.339, 0.154) g | max: 0.860 g
01:42:35.494 -> raw:( -1693, 784, -140) | cal:( 0.191, 0.413, -0.034) g | max: 0.860 g
01:42:35.595 -> raw:( -1465, 573, 284) | cal:( 0.140, 0.358, 0.069) g | max: 0.860 g
01:42:35.690 -> raw:( -1696, 429, 1057) | cal:( 0.105, 0.414, 0.258) g | max: 0.860 g
01:42:35.787 -> raw:( -1440, 805, 1790) | cal:( 0.197, 0.352, 0.437) g | max: 0.860 g
01:42:35.884 -> raw:( -1463, 1134, 1462) | cal:( 0.277, 0.357, 0.357) g | max: 0.860 g
01:42:36.014 -> raw:( -1363, 429, 1725) | cal:( 0.105, 0.333, 0.421) g | max: 0.860 g
01:42:36.111 -> raw:( -1410, 51, 1699) | cal:( 0.012, 0.344, 0.415) g | max: 0.860 g
01:42:36.208 -> raw:( -1716, 291, 1289) | cal:( 0.071, 0.419, 0.315) g | max: 0.860 g
01:42:36.307 -> raw:( -1965, 11, 1132) | cal:( 0.003, 0.480, 0.276) g | max: 0.860 g
01:42:36.403 -> raw:( -2043, -119, 902) | cal:( -0.029, 0.499, 0.220) g | max: 0.860 g
01:42:36.500 -> raw:( -2078, -118, 381) | cal:( -0.029, 0.507, 0.093) g | max: 0.860 g
01:42:36.631 -> raw:( -1926, 231, 8) | cal:( 0.056, 0.470, 0.002) g | max: 0.860 g
01:42:36.723 -> raw:( -2113, 53, 300) | cal:( 0.013, 0.516, 0.073) g | max: 0.860 g
01:42:36.820 -> raw:( -1900, 421, 239) | cal:( 0.103, 0.464, 0.058) g | max: 0.860 g
01:42:36.918 -> raw:( -1747, 965, 128) | cal:( 0.236, 0.427, 0.031) g | max: 0.860 g
01:42:37.015 -> raw:( -1867, 448, 595) | cal:( 0.109, 0.456, 0.145) g | max: 0.860 g
01:42:37.144 -> raw:( -1795, 1489, -265) | cal:( 0.364, 0.438, -0.065) g | max: 0.860 g
01:42:37.241 -> raw:( -1763, 680, 379) | cal:( 0.166, 0.430, 0.093) g | max: 0.860 g
01:42:37.338 -> raw:( -1572, 1211, 503) | cal:( 0.296, 0.384, 0.123) g | max: 0.860 g
01:42:37.435 -> raw:( -832, 2299, 412) | cal:( 0.561, 0.203, 0.101) g | max: 0.860 g
01:42:37.530 -> raw:( -386, 3278, 551) | cal:( 0.800, 0.094, 0.135) g | max: 0.860 g
01:42:37.629 -> raw:( -2482, -7826, 934) | cal:( -1.911, 0.606, 0.228) g | max: 1.911 g
01:42:37.760 -> raw:( -1317, -62, -167) | cal:( -0.015, 0.322, -0.041) g | max: 1.911 g
01:42:37.855 -> raw:( -124, 2031, 685) | cal:( 0.496, 0.030, 0.167) g | max: 1.911 g
01:42:37.952 -> raw:( 403, 4865, 310) | cal:( 1.188, -0.098, 0.076) g | max: 1.911 g
01:42:38.048 -> raw:( -3890,-10370, 860) | cal:( -2.532, 0.950, 0.210) g | max: 2.532 g
01:42:38.145 -> raw:( -1226, 133, 217) | cal:( 0.032, 0.299, 0.053) g | max: 2.532 g
01:42:38.275 -> raw:( 477, 4082, 686) | cal:( 0.997, -0.116, 0.167) g | max: 2.532 g
01:42:38.372 -> raw:( -195, 1743, -376) | cal:( 0.426, 0.048, -0.092) g | max: 2.532 g
01:42:38.469 -> raw:( -3855, -4533, 79) | cal:( -1.107, 0.941, 0.019) g | max: 2.532 g
01:42:38.566 -> raw:( -1091, 2005, -86) | cal:( 0.490, 0.266, -0.021) g | max: 2.532 g
01:42:38.662 -> raw:( -739, 3462, -454) | cal:( 0.845, 0.180, -0.111) g | max: 2.532 g
01:42:38.791 -> raw:( -3563, -6396, 3031) | cal:( -1.562, 0.870, 0.740) g | max: 2.532 g
01:42:38.887 -> raw:( -1236, 299, 106) | cal:( 0.073, 0.302, 0.026) g | max: 2.532 g
01:42:38.983 -> raw:( 390, 4130, 168) | cal:( 1.008, -0.095, 0.041) g | max: 2.532 g
01:42:39.080 -> raw:( -1342, -972, 58) | cal:( -0.237, 0.328, 0.014) g | max: 2.532 g
01:42:39.176 -> raw:( -1010, -359, 81) | cal:( -0.088, 0.247, 0.020) g | max: 2.532 g
01:42:39.273 -> raw:( 1680, 7193, 592) | cal:( 1.756, -0.410, 0.145) g | max: 2.532 g
01:42:39.402 -> raw:( -5847,-11882, -2385) | cal:( -2.901, 1.427, -0.582) g | max: 4.338 g
01:42:39.498 -> raw:( 7649, 20628, 5632) | cal:( 5.036, -1.867, 1.375) g | max: 5.036 g
01:42:39.595 -> raw:( 4671, -693, -1943) | cal:( -0.169, -1.140, -0.474) g | max: 8.000 g
01:42:39.693 -> raw:( 5063,-22066, -8290) | cal:( -5.387, -1.236, -2.024) g | max: 8.000 g
01:42:39.789 -> raw:( 10913, 18266, 10504) | cal:( 4.459, -2.664, 2.564) g | max: 8.000 g
01:42:39.918 -> raw:( 2049, 1771, -3083) | cal:( 0.432, -0.500, -0.753) g | max: 8.000 g
01:42:40.014 -> raw:( -2707,-31850,-19850) | cal:( -7.776, 0.661, -4.846) g | max: 8.000 g
01:42:40.111 -> raw:( 14881, 23445, 14769) | cal:( 5.724, -3.633, 3.606) g | max: 8.000 g
01:42:40.208 -> raw:( 6386, 1240, 3070) | cal:( 0.303, -1.559, 0.750) g | max: 8.000 g
01:42:40.305 -> raw:(-12005,-32768,-26427) | cal:( -8.000, 2.931, -6.452) g | max: 8.000 g
01:42:40.402 -> raw:( 16923, 28766, 15105) | cal:( 7.023, -4.132, 3.688) g | max: 8.000 g
01:42:40.531 -> raw:( 14395, 8961, 10771) | cal:( 2.188, -3.514, 2.630) g | max: 8.000 g
01:42:40.629 -> raw:( -5563,-14877,-15483) | cal:( -3.632, 1.358, -3.780) g | max: 8.000 g
01:42:40.725 -> raw:( 19418, 10198, 7290) | cal:( 2.490, -4.741, 1.780) g | max: 8.000 g
01:42:40.824 -> raw:( 20157, 23506, 18807) | cal:( 5.739, -4.921, 4.592) g | max: 8.000 g
01:42:40.920 -> raw:( -615, -3815, -8656) | cal:( -0.931, 0.150, -2.113) g | max: 8.000 g
01:42:41.015 -> raw:( 13797,-23456,-26078) | cal:( -5.727, -3.368, -6.367) g | max: 8.000 g
01:42:41.145 -> raw:( 19016, 32767, 22780) | cal:( 8.000, -4.643, 5.562) g | max: 8.000 g
01:42:41.242 -> raw:( 8411, -3145, -4444) | cal:( -0.768, -2.053, -1.085) g | max: 8.000 g
01:42:41.339 -> raw:( -9110,-32768,-32768) | cal:( -8.000, 2.224, -8.000) g | max: 8.000 g
...