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AP_InertialSensor: support for fast sampling rates on ICM-42xxx series 

thoughtfully set anti-aliasing filters on ICM-42xxx series
This commit is contained in:
Andy Piper 2022-07-20 17:47:24 +01:00 committed by Andrew Tridgell
parent 696cd1a19b
commit 155d436807
2 changed files with 201 additions and 43 deletions
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224
libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.cpp
View File

@ -19,7 +19,7 @@
ICM-40609
ICM-42688
ICM-42605
ICM-40605
ICM-40605 - EOL
IIM-42652
ICM-42670
@ -32,6 +32,7 @@
#include <AP_HAL/AP_HAL.h>
#include "AP_InertialSensor_Invensensev3.h"
#include <utility>
#include <stdio.h>
extern const AP_HAL::HAL& hal;
@ -49,6 +50,9 @@ static const float GYRO_SCALE = (0.0174532f / 16.4f);
#define INV3REG_PWR_MGMT0 0x4e
#define INV3REG_GYRO_CONFIG0 0x4f
#define INV3REG_ACCEL_CONFIG0 0x50
#define INV3REG_GYRO_CONFIG1 0x51
#define INV3REG_GYRO_ACCEL_CONFIG0 0x52
#define INV3REG_ACCEL_CONFIG1 0x53
#define INV3REG_FIFO_CONFIG1 0x5f
#define INV3REG_FIFO_CONFIG2 0x60
#define INV3REG_FIFO_CONFIG3 0x61
@ -219,17 +223,21 @@ void AP_InertialSensor_Invensensev3::start()
// always use FIFO
fifo_reset();
if (!_imu.register_gyro(gyro_instance, expected_ODR, dev->get_bus_id_devtype(devtype)) ||
!_imu.register_accel(accel_instance, expected_ODR, dev->get_bus_id_devtype(devtype))) {
// setup on-sensor filtering and scaling and backend rate
if (inv3_type == Invensensev3_Type::ICM42670) {
set_filter_and_scaling_icm42670();
} else {
set_filter_and_scaling();
}
if (!_imu.register_gyro(gyro_instance, backend_rate_hz, dev->get_bus_id_devtype(devtype)) ||
!_imu.register_accel(accel_instance, backend_rate_hz, dev->get_bus_id_devtype(devtype))) {
return;
}
// setup on-sensor filtering and scaling
set_filter_and_scaling();
// update backend sample rate
_set_accel_raw_sample_rate(accel_instance, expected_ODR);
_set_gyro_raw_sample_rate(gyro_instance, expected_ODR);
_set_accel_raw_sample_rate(accel_instance, backend_rate_hz);
_set_gyro_raw_sample_rate(gyro_instance, backend_rate_hz);
// indicate what multiplier is appropriate for the sensors'
// readings to fit them into an int16_t:
@ -248,8 +256,18 @@ void AP_InertialSensor_Invensensev3::start()
AP_HAL::panic("Invensensev3: Unable to allocate FIFO buffer");
}
// start the timer process to read samples
dev->register_periodic_callback(1e6 / expected_ODR, FUNCTOR_BIND_MEMBER(&AP_InertialSensor_Invensensev3::read_fifo, void));
// start the timer process to read samples, using the fastest rate avilable
dev->register_periodic_callback(1000000UL / backend_rate_hz, FUNCTOR_BIND_MEMBER(&AP_InertialSensor_Invensensev3::read_fifo, void));
}
// get a startup banner to output to the GCS
bool AP_InertialSensor_Invensensev3::get_output_banner(char* banner, uint8_t banner_len) {
if (fast_sampling) {
snprintf(banner, banner_len, "IMU%u: fast sampling enabled %.1fkHz",
gyro_instance, backend_rate_hz * 0.001);
return true;
}
return false;
}
/*
@ -420,32 +438,176 @@ void AP_InertialSensor_Invensensev3::register_write_bank(uint8_t bank, uint8_t r
/*
set the filter frequencies and scaling
The AAF for gyros needs to be high enough to avoid group delay and low enough to have
(ideally) 40dB at the nyquist frequency so that noise above this is not folded into the
range seen by ArduPilot. A reasonable approximation for the former is 1Khz and for the latter
1/4 of the sample frequency, so for 1/4 sample frequency > 1Khz we pick 1Khz and for 1/4 sample
frequency < 1Khz we use 1/4 sample frequency.
The AAF for accels is set lower to minimise noise and clipping. The constraint is that the
group delay between gyros and accels should be <5ms to avoid inertial nav errors.
The UI filter block cannot be disabled and is fixed at ODR/4. This is a 2p filter by default
(as is the AAF). Since the order of the UI filter does not appear to significantly affect
group delay at higher ODRs it is left at the default. The group delay of the AAF is not documented,
but we assume it is similar to the UI 2p performance:
2Khz - 0.2ms
1Khz - 0.4ms
666Hz - 0.6ms
500Hz - 0.8ms
333Hz - 2.0ms
190Hz - 2.4ms
Since the UI group delay is the same for both accels and gyros we only need to consider the
difference in group delay for the AAFs. At the highest ODR of 4Khz or 8Khz the group delay for
gyros will be 0.4ms thus the accel AAF can safely be set to ~190Hz.
*/
void AP_InertialSensor_Invensensev3::set_filter_and_scaling(void)
{
if (inv3_type == Invensensev3_Type::ICM42670) {
// use low-noise mode
register_write(INV3REG_70_PWR_MGMT0, 0x0f);
hal.scheduler->delay_microseconds(300);
// 1KHz by default
backend_rate_hz = 1000;
uint8_t odr_config = 0x06;
// setup gyro for 1.6kHz, with 180Hz LPF
register_write(INV3REG_70_GYRO_CONFIG0, 0x05);
register_write(INV3REG_70_GYRO_CONFIG1, 0x01);
// AAF at ~1/4 of 1Khz by default for gyros- 258Hz
// AAF at 213Hz for accels
uint8_t aaf_delt = 6, accel_aaf_delt = 5;
uint16_t aaf_deltsqr = 36, accel_aaf_deltsqr = 25;
uint8_t aaf_bitshift = 10, accel_aaf_bitshift = 10;
// setup accel for 1.6kHz, with 180Hz LPF
register_write(INV3REG_70_ACCEL_CONFIG0, 0x05);
register_write(INV3REG_70_ACCEL_CONFIG1, 0x01);
// limited filtering on ICM-42605
if (inv3_type == Invensensev3_Type::ICM42605) {
// 249Hz AAF gyros
aaf_delt = 21;
aaf_deltsqr = 440;
aaf_bitshift = 6;
// 184Hz AAF accels
accel_aaf_delt = 16;
accel_aaf_deltsqr = 256;
accel_aaf_bitshift = 7;
}
// checked for
// ICM-40609
// ICM-42688
// ICM-42605
// IIM-42652
if (enable_fast_sampling(accel_instance) && get_fast_sampling_rate() > 1) {
fast_sampling = dev->bus_type() == AP_HAL::Device::BUS_TYPE_SPI;
if (fast_sampling) {
// constrain the gyro rate to be at least the loop rate
uint8_t loop_limit = 1;
if (get_loop_rate_hz() > 1000) {
loop_limit = 2;
}
if (get_loop_rate_hz() > 2000) {
loop_limit = 4;
}
// constrain the gyro rate to be a 2^N multiple
uint8_t fast_sampling_rate = constrain_int16(get_fast_sampling_rate(), loop_limit, 8);
// calculate rate we will be giving samples to the backend
backend_rate_hz *= fast_sampling_rate;
// limited filtering on ICM-42605
if (inv3_type == Invensensev3_Type::ICM42605) {
switch (fast_sampling_rate) {
case 2: // 2KHz
odr_config = 0x05;
// 507Hz AAF
aaf_delt = 47;
aaf_deltsqr = 2208;
aaf_bitshift = 4;
break;
case 4: // 4KHz
// 995Hz AAF
aaf_delt = 63;
aaf_deltsqr = 3968;
aaf_bitshift = 3;
odr_config = 0x04;
break;
case 8: // 8Khz
// 995Hz AAF
aaf_delt = 63;
aaf_deltsqr = 3968;
aaf_bitshift = 3;
odr_config = 0x03;
break;
default: // 1Khz, 334Hz AAF
break;
}
} else {
// ICM-42688 / ICM-40609 / IIM-426525
switch (fast_sampling_rate) {
case 2: // 2KHz
odr_config = 0x05;
// 536Hz AAF
aaf_delt = 12;
aaf_deltsqr = 144;
aaf_bitshift = 8;
break;
case 4: // 4KHz
odr_config = 0x04;
// 997Hz AAF
aaf_delt = 21;
aaf_deltsqr = 440;
aaf_bitshift = 6;
break;
case 8: // 8Khz
odr_config = 0x03;
// 997Hz AAF
aaf_delt = 21;
aaf_deltsqr = 440;
aaf_bitshift = 6;
break;
default: // 1KHz, 348Hz AAF
break;
}
}
}
}
// enable gyro and accel in low-noise modes
register_write(INV3REG_PWR_MGMT0, 0x0F);
hal.scheduler->delay_microseconds(300);
// setup gyro for 2kHz
register_write(INV3REG_GYRO_CONFIG0, 0x05);
// setup gyro for backend rate
register_write(INV3REG_GYRO_CONFIG0, odr_config);
// setup accel for backend rate
register_write(INV3REG_ACCEL_CONFIG0, odr_config);
// setup accel for 2kHz
register_write(INV3REG_ACCEL_CONFIG0, 0x05);
}
// setup anti-alias filters for gyro at 1/4 ODR, notch left at default
register_write_bank(1, INV3REG_GYRO_CONFIG_STATIC3, aaf_delt); // GYRO_AAF_DELT
register_write_bank(1, INV3REG_GYRO_CONFIG_STATIC4, (aaf_deltsqr & 0xFF)); // GYRO_AAF_DELTSQR
register_write_bank(1, INV3REG_GYRO_CONFIG_STATIC5, ((aaf_bitshift<<4) & 0xF0) | ((aaf_deltsqr>>8) & 0x0F)); // GYRO_AAF_BITSHIFT | GYRO_AAF_DELTSQR
// setup accel AAF at fixed ~500Hz
register_write_bank(2, INV3REG_ACCEL_CONFIG_STATIC2, accel_aaf_delt<<1); // ACCEL_AAF_DELT | enabled bit
register_write_bank(2, INV3REG_ACCEL_CONFIG_STATIC3, (accel_aaf_deltsqr & 0xFF)); // ACCEL_AAF_DELTSQR
register_write_bank(2, INV3REG_ACCEL_CONFIG_STATIC4, ((accel_aaf_bitshift<<4) & 0xF0) | ((accel_aaf_deltsqr>>8) & 0x0F)); // ACCEL_AAF_BITSHIFT | ACCEL_AAF_DELTSQR
}
/*
set the filter frequencies and scaling for the ICM-42670
*/
void AP_InertialSensor_Invensensev3::set_filter_and_scaling_icm42670(void)
{
backend_rate_hz = 1600;
// use low-noise mode
register_write(INV3REG_70_PWR_MGMT0, 0x0f);
hal.scheduler->delay_microseconds(300);
// setup gyro for 1.6kHz, 2000dps range
register_write(INV3REG_70_GYRO_CONFIG0, 0x05);
// Low noise mode uses an AAF with fixed bandwidth, so disable LPF
register_write(INV3REG_70_GYRO_CONFIG1, 0x30);
// setup accel for 1.6kHz, 16g range
register_write(INV3REG_70_ACCEL_CONFIG0, 0x05);
// AAF is not available for accels, so LPF at 180Hz
register_write(INV3REG_70_ACCEL_CONFIG1, 0x01);
}
/*
@ -454,7 +616,6 @@ void AP_InertialSensor_Invensensev3::set_filter_and_scaling(void)
bool AP_InertialSensor_Invensensev3::check_whoami(void)
{
uint8_t whoami = register_read(INV3REG_WHOAMI);
expected_ODR = 2000;
switch (whoami) {
case INV3_ID_ICM40609:
@ -480,7 +641,6 @@ bool AP_InertialSensor_Invensensev3::check_whoami(void)
case INV3_ID_ICM42670:
inv3_type = Invensensev3_Type::ICM42670;
accel_scale = (GRAVITY_MSS / 2048);
expected_ODR = 1600;
return true;
}
// not a value WHOAMI result
@ -543,16 +703,6 @@ bool AP_InertialSensor_Invensensev3::hardware_init(void)
// little-endian, fifo count in records
register_write(INV3REG_70_INTF_CONFIG0, 0x40, true);
}
if (inv3_type == Invensensev3_Type::ICM42688) {
// setup anti-alias filters for 488Hz on gyro and accel, notch left at default
register_write_bank(1, INV3REG_GYRO_CONFIG_STATIC3, 11); // GYRO_AAF_DELT
register_write_bank(1, INV3REG_GYRO_CONFIG_STATIC4, 122); // GYRO_AAF_DELTSQR
register_write_bank(1, INV3REG_GYRO_CONFIG_STATIC5, 0x80); // GYRO_AAF_BITSHIFT&GYRO_AAF_DELTSQR
register_write_bank(2, INV3REG_ACCEL_CONFIG_STATIC2, 11U<<1);
register_write_bank(2, INV3REG_ACCEL_CONFIG_STATIC3, 122);
register_write_bank(2, INV3REG_ACCEL_CONFIG_STATIC4, 0x80);
}
return true;
}

10
libraries/AP_InertialSensor/AP_InertialSensor_Invensensev3.h
View File

@ -28,6 +28,8 @@ public:
void accumulate() override;
void start() override;
// get a startup banner to output to the GCS
bool get_output_banner(char* banner, uint8_t banner_len) override;
enum class Invensensev3_Type : uint8_t {
ICM40609 = 0,
@ -51,6 +53,7 @@ private:
bool check_whoami();
void set_filter_and_scaling(void);
void set_filter_and_scaling_icm42670(void);
void fifo_reset();
/* Read samples from FIFO */
@ -79,7 +82,12 @@ private:
const enum Rotation rotation;
float accel_scale;
float expected_ODR;
// are we doing more than 1kHz sampling?
bool fast_sampling;
// what rate are we generating samples into the backend for gyros and accels?
uint16_t backend_rate_hz;
AP_HAL::OwnPtr<AP_HAL::Device> dev;