Demo
BMI160 SPI Sensor Emulator Demo
This hardware-in-the-loop demo physically replaces a BMI160 accelerometer with the RH01T9k emulator while the ESP32 runs the same firmware.
Physical sensor
ESP32 <---- SPI ----> BMI160
|
SSD1306 OLEDEmulated sensor
ESP32 <---- SPI ----> RH01T9k
|
SSD1306 OLEDDemo video
The ESP32 first reads acceleration data from a physical BMI160 over SPI and displays X/Y/Z values on an OLED.
The BMI160 is then replaced by the RH01T9k. The ESP32 firmware remains unchanged and continues issuing the same SPI transactions, while RH01T9k returns simulated BMI160 register data configured from Python.
The X/Y/Z accelerometer values include the effect of gravity. At 0°, the sensor reports approximately X = 0 g, Y = 0 g, Z = -1 g. At 90°, it reports approximately X = +1 g, Y = 0 g, Z = 0 g.
ESP32 firmware
The ESP32 firmware used in this demo is available on GitHub:
The same firmware is used with both the physical BMI160 and the RH01T9k emulator.
Python emulator script
The following script configures RH01T9k as a BMI160-compatible SPI peripheral and generates a repeatable tilt sequence.
"""
BMI160 emulator - scripted motion demo.
The SPI slave emulator synthesizes a
motion sequence:
flat
->
45 degree tilt
->
90 degree tilt
->
hold
->
return flat
"""
import math
import time
from hil import HIL, RegisterDevice
# ============================================================
# Connection
# ============================================================
PORT = "COM7"
BAUD = 115200
# ============================================================
# BMI160 registers
# ============================================================
REG_CHIP_ID = 0x00
REG_PMU_STATUS = 0x03
REG_ACC_X_L = 0x12
REG_ACC_X_H = 0x13
REG_ACC_Y_L = 0x14
REG_ACC_Y_H = 0x15
REG_ACC_Z_L = 0x16
REG_ACC_Z_H = 0x17
REG_ACC_CONF = 0x40
REG_ACC_RANGE = 0x41
REG_CMD = 0x7E
# ============================================================
# BMI160 constants
# ============================================================
BMI160_CHIP_ID = 0xD1
PMU_STATUS_ACC_NORMAL = 0x10
ACC_CONF_100HZ = 0x28
ACC_RANGE_2G = 0x03
LSB_PER_G = 16384
# ============================================================
# Atomic window
# ============================================================
ACC_ATOMIC_START = REG_ACC_X_L
ACC_ATOMIC_LENGTH = 6
# ============================================================
# Motion configuration
# ============================================================
UPDATE_MS = 50
FLAT_HOLD_MS = 1000
TILT_TIME_MS = 1500
ANGLE_HOLD_MS = 1000
RETURN_TIME_MS = 1500
# ============================================================
# Conversion helpers
# ============================================================
def clamp_int16(value: int) -> int:
return max(
-32768,
min(32767, int(value)),
)
def g_to_raw(g_value: float) -> int:
return clamp_int16(
round(g_value * LSB_PER_G)
)
def int16_to_le(value: int) -> tuple[int, int]:
value = clamp_int16(value)
if value < 0:
value += 0x10000
return (
value & 0xFF,
(value >> 8) & 0xFF,
)
# ============================================================
# Accelerometer register update
# ============================================================
def set_accel(
dev: HIL,
x_g: float,
y_g: float,
z_g: float,
):
raw_x = g_to_raw(x_g)
raw_y = g_to_raw(y_g)
raw_z = g_to_raw(z_g)
x_l, x_h = int16_to_le(raw_x)
y_l, y_h = int16_to_le(raw_y)
z_l, z_h = int16_to_le(raw_z)
sample = [
x_l,
x_h,
y_l,
y_h,
z_l,
z_h,
]
# Stage all six accelerometer registers, then commit them
# together between SPI transactions.
dev.spi.update_atomic(
ACC_ATOMIC_START,
sample,
)
# ============================================================
# Motion model
# ============================================================
def set_tilt_angle(
dev: HIL,
angle_deg: float,
):
"""
Simulate rotating the sensor around Y.
0 degrees:
X = 0
Z = -1 g
90 degrees:
X = +1 g
Z = 0
"""
angle_rad = math.radians(angle_deg)
x_g = math.sin(angle_rad)
y_g = 0.0
z_g = -math.cos(angle_rad)
set_accel(
dev,
x_g,
y_g,
z_g,
)
print(
f"angle={angle_deg:6.1f} deg "
f"X={x_g:+.3f} g "
f"Y={y_g:+.3f} g "
f"Z={z_g:+.3f} g"
)
def hold_angle(
dev: HIL,
angle_deg: float,
duration_ms: int,
):
steps = max(
1,
duration_ms // UPDATE_MS,
)
for _ in range(steps):
set_tilt_angle(
dev,
angle_deg,
)
time.sleep(
UPDATE_MS / 1000
)
def move_angle(
dev: HIL,
start_deg: float,
end_deg: float,
duration_ms: int,
):
steps = max(
1,
duration_ms // UPDATE_MS,
)
for step in range(steps + 1):
fraction = step / steps
angle_deg = (
start_deg
+ (end_deg - start_deg)
* fraction
)
set_tilt_angle(
dev,
angle_deg,
)
time.sleep(
UPDATE_MS / 1000
)
# ============================================================
# BMI160 register model
# ============================================================
bmi160 = RegisterDevice(
mode=0,
default_miso=0x00,
# bit 7 = read/write
read_mask=0x80,
read_value=0x80,
write_mask=0x80,
write_value=0x00,
# 7-bit BMI160 register address
address_mask=0x7F,
address_shift=0,
# Auto increment during reads.
auto_increment_mask=0x80,
auto_increment_value=0x80,
response_delay_bytes=0,
)
# ============================================================
# Initial register values
# ============================================================
bmi160[REG_CHIP_ID] = BMI160_CHIP_ID
bmi160[REG_PMU_STATUS] = PMU_STATUS_ACC_NORMAL
bmi160[REG_ACC_CONF] = ACC_CONF_100HZ
bmi160[REG_ACC_RANGE] = ACC_RANGE_2G
bmi160[REG_CMD] = 0x00
# Start flat:
#
# X = 0
# Y = 0
# Z = -1 g
bmi160.load(
[
0x00, 0x00,
0x00, 0x00,
0x00, 0xC0,
],
start=REG_ACC_X_L,
)
# ============================================================
# Run emulator
# ============================================================
with HIL(PORT, BAUD) as dev:
dev.ping()
dev.clear_errors()
print()
print("Loading BMI160 FPGA emulator...")
# Load initial register image first.
dev.spi.emulate_registers(
bmi160
)
# Then define the six accelerometer registers as one
# coherent atomic-update window.
dev.spi.configure_atomic_window(
ACC_ATOMIC_START,
ACC_ATOMIC_LENGTH,
)
print("BMI160 emulator ready")
print(
f"Atomic accel window: "
f"0x{ACC_ATOMIC_START:02X}.."
f"0x{ACC_ATOMIC_START + ACC_ATOMIC_LENGTH - 1:02X}"
)
print("ESP32 firmware remains unchanged")
print()
try:
while True:
# ------------------------------------------------
# 1. Flat
# ------------------------------------------------
print()
print("=== FLAT ===")
hold_angle(
dev,
angle_deg=0,
duration_ms=FLAT_HOLD_MS,
)
# ------------------------------------------------
# 2. Slowly tilt to 45 degrees
# ------------------------------------------------
print()
print("=== TILT TO 45 DEG ===")
move_angle(
dev,
start_deg=0,
end_deg=45,
duration_ms=TILT_TIME_MS,
)
# ------------------------------------------------
# 3. Hold 45 degrees
# ------------------------------------------------
print()
print("=== HOLD 45 DEG ===")
hold_angle(
dev,
angle_deg=45,
duration_ms=ANGLE_HOLD_MS,
)
# ------------------------------------------------
# 4. Tilt to 90 degrees
# ------------------------------------------------
print()
print("=== TILT TO 90 DEG ===")
move_angle(
dev,
start_deg=45,
end_deg=90,
duration_ms=TILT_TIME_MS,
)
# ------------------------------------------------
# 5. Hold sideways
# ------------------------------------------------
print()
print("=== HOLD 90 DEG ===")
hold_angle(
dev,
angle_deg=90,
duration_ms=ANGLE_HOLD_MS,
)
# ------------------------------------------------
# 6. Return to flat
# ------------------------------------------------
print()
print("=== RETURN TO FLAT ===")
move_angle(
dev,
start_deg=90,
end_deg=0,
duration_ms=RETURN_TIME_MS,
)
except KeyboardInterrupt:
print()
print("BMI160 emulator stopped")