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Configure LSM9DS1 hardware lowpass filters
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On initialization, configure use of hardware lowpass filters in the
LSM9DS1 sensor. This commit sets the gyroscope lowpass cutoff frequency
to 19 Hz and accelerometer lowpass cutoff frequency to 1 Hz.

Change-Id: I1e7f04438646e44a9f1c35ab6b67bb949b521a69
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@oliverlee
oliverlee committed Jul 27, 2023
1 parent 39e98b2 commit 72af018
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Showing 2 changed files with 75 additions and 50 deletions.
122 changes: 74 additions & 48 deletions LSM9DS1_MEMS/LSM9DS1_MEMS.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,9 @@ extern "C" {
class LSM9DS1
{
public:
LSM9DS1(const char* device, uint8_t address)
using scalar_type = float;

LSM9DS1(const char* device)
{
// NOLINTBEGIN(cppcoreguidelines-prefer-member-initializer,
// cppcoreguidelines-pro-type-vararg)
Expand All @@ -79,30 +81,31 @@ class LSM9DS1
// cppcoreguidelines-pro-type-vararg)
assert((device_ >= 0) and "error in opening device");

static constexpr auto addr = 0x6B;

// NOLINTNEXTLINE(cppcoreguidelines-pro-type-vararg)
auto set_addr_status = ::ioctl(device_, I2C_SLAVE, address);
auto set_addr_status = ::ioctl(device_, I2C_SLAVE, addr);
assert((set_addr_status >= 0) and "error specifying i2c device address");

init_gyro();
init_accel();
}

auto read_gx() -> int16_t
auto read_gx() const -> std::int16_t
{
auto raw = i2c_read(OUT_X_L_G);
return raw;
}

struct Accel
{
int16_t y;
int16_t z;
std::int16_t y;
std::int16_t z;

[[nodiscard]]
auto get_theta() const -> float
auto get_theta() const -> scalar_type
{
// GCC cannot find `std::atan2f`
return std::atan2(float(y), float(z));
return std::atan2(scalar_type(y), scalar_type(z));
}
};

Expand All @@ -118,82 +121,105 @@ class LSM9DS1
private:
int device_;

auto i2c_write(uint8_t subaddress, uint8_t data) const -> void
auto i2c_write(std::uint8_t subaddress, std::uint8_t data) const -> void
{
auto status = ::i2c_smbus_write_byte_data(device_, subaddress, data);
assert((status == 0) and "Failed to write data");
}

[[nodiscard]]
auto i2c_read(uint8_t subaddress) const -> int16_t
auto i2c_read(std::uint8_t subaddress) const -> std::int16_t
{
auto response = ::i2c_smbus_read_word_data(device_, subaddress);
assert((response >= 0) and "Failed to read data");

// NOLINTNEXTLINE(readability-magic-numbers)
auto as_s16 = int16_t(response & 0xFFFF);
auto as_s16 = std::int16_t(response & 0xFFFF);

return as_s16;
}

auto init_gyro() -> void
{
uint8_t tempRegValue = 0;
// NOLINTBEGIN(readability-magic-numbers)

// CTRL_REG1_G
tempRegValue = 0;
// NOLINTBEGIN(readability-magic-numbers)
tempRegValue |= (1 << 7);
tempRegValue |= (1 << 6);
// NOLINTEND(readability-magic-numbers)
i2c_write(CTRL_REG1_G, tempRegValue);
{
static constexpr std::uint8_t ODR_60Hz_LPF1_19Hz = 0b010 << 5;
static constexpr std::uint8_t FS_245dps = 0b00 << 3;
static constexpr std::uint8_t BW_00 = 0b00;
i2c_write(CTRL_REG1_G, ODR_60Hz_LPF1_19Hz | FS_245dps | BW_00);
}

// CTRL_REG2_G
tempRegValue = 0;
i2c_write(CTRL_REG2_G, tempRegValue);
{
static constexpr std::uint8_t INT_SEL = 0b00 << 2;
static constexpr std::uint8_t OUT_SEL = 0b00;
i2c_write(CTRL_REG2_G, INT_SEL | OUT_SEL);
}

// CTRL_REG3_G
tempRegValue = 0;
i2c_write(CTRL_REG3_G, tempRegValue);
{
static constexpr std::uint8_t LP_disabled = 0b0 << 7;
static constexpr std::uint8_t HPF_disabled = 0b0 << 6;
static constexpr std::uint8_t HPCF_G_0000 = 0b0000;
i2c_write(CTRL_REG3_G, LP_disabled | HPF_disabled | HPCF_G_0000);
}

// CTRL_REG4
tempRegValue = 0;
tempRegValue |= (1 << 3); // X axis
tempRegValue |= (1 << 1); // latch interrupt
i2c_write(CTRL_REG4, tempRegValue);

// CFG_G
tempRegValue = 0;
i2c_write(INT_GEN_CFG_G, tempRegValue);
{
static constexpr std::uint8_t Z_disable = 0b0 << 5;
static constexpr std::uint8_t Y_disable = 0b0 << 4;
static constexpr std::uint8_t X_enable = 0b1 << 3;
static constexpr std::uint8_t LatchedInterrupt_disable = 0b0 << 1;

i2c_write(
CTRL_REG4,
Z_disable | Y_disable | X_enable | LatchedInterrupt_disable);
}

// NOLINTEND(readability-magic-numbers)
}

auto init_accel() -> void
{
uint8_t tempRegValue = 0;
// NOLINTBEGIN(readability-magic-numbers)

// CTRL_REG5_XL
tempRegValue = 0;
// NOLINTBEGIN(readability-magic-numbers)
tempRegValue |= (1 << 5);
tempRegValue |= (1 << 4);
// NOLINTEND(readability-magic-numbers)
i2c_write(CTRL_REG5_XL, tempRegValue);
{
static constexpr std::uint8_t DEC_none = 0b00 << 6;
static constexpr std::uint8_t Z_enable = 0b1 << 5;
static constexpr std::uint8_t Y_enable = 0b1 << 4;
static constexpr std::uint8_t X_disable = 0b0 << 3;
i2c_write(CTRL_REG5_XL, DEC_none | Z_enable | Y_enable | X_disable);
}

// CTRL_REG6_XL
tempRegValue = 0;
// NOLINTBEGIN(readability-magic-numbers)
tempRegValue |= (1 << 7);
tempRegValue |= (1 << 6);
// NOLINTEND(readability-magic-numbers)
i2c_write(CTRL_REG6_XL, tempRegValue);
{
static constexpr std::uint8_t ODR_50Hz = 0b010 << 5;
static constexpr std::uint8_t FS_4g = 0b10 << 3;
static constexpr std::uint8_t BW_sel = 0b1 << 2;
static constexpr std::uint8_t BW_50Hz = 0b11;
i2c_write(CTRL_REG6_XL, ODR_50Hz | FS_4g | BW_sel | BW_50Hz);
}

// CTRL_REG7_XL
tempRegValue = 0;
i2c_write(CTRL_REG7_XL, tempRegValue);
{
static constexpr std::uint8_t HR_enable = 0b1 << 7;
static constexpr std::uint8_t LPF_ODR_div_50 = 0b00 << 5;
static constexpr std::uint8_t LPF_enable = 0b1 << 2;
static constexpr std::uint8_t HP_int_disable = 0b0;
i2c_write(
CTRL_REG7_XL,
HR_enable | LPF_ODR_div_50 | LPF_enable | HP_int_disable);
}

// CTRL_REG8
tempRegValue = 0;
tempRegValue |= (1 << 1); // Endianness
i2c_write(CTRL_REG8, tempRegValue);
{
static constexpr std::uint8_t BLE_little = 0b1 << 1;
i2c_write(CTRL_REG8, BLE_little);
}

// NOLINTEND(readability-magic-numbers)
}
};
3 changes: 1 addition & 2 deletions examples/i2c.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13,8 +13,7 @@ auto main(int argc, char** argv) -> int

// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-pointer-arithmetic)
const auto& device = argv[1];
constexpr auto i2c_address = 0x6b;
auto sensor = LSM9DS1{device, i2c_address};
auto sensor = LSM9DS1{device};

// NOLINTNEXTLINE(readability-magic-numbers)
for (auto i = 0; i < 100; ++i) {
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