117 lines
3.5 KiB
Python
117 lines
3.5 KiB
Python
from machine import Pin
|
|
import time
|
|
import json
|
|
import os
|
|
|
|
CALIB_FILE = "calibration.cfg"
|
|
|
|
|
|
# ---------------------------------------------------------
|
|
# Calibration File Helpers
|
|
# ---------------------------------------------------------
|
|
|
|
def save_calibration(zero_offset, scale_factor):
|
|
"""Save calibration values to internal flash."""
|
|
data = {
|
|
"zero_offset": zero_offset,
|
|
"scale_factor": scale_factor
|
|
}
|
|
with open(CALIB_FILE, "w") as f:
|
|
json.dump(data, f)
|
|
print("✔ Calibration saved.")
|
|
|
|
|
|
def load_calibration():
|
|
"""Load existing calibration or return defaults."""
|
|
if CALIB_FILE not in os.listdir():
|
|
print("⚠ No calibration file found, using defaults.")
|
|
return 0, 1
|
|
|
|
try:
|
|
with open(CALIB_FILE, "r") as f:
|
|
data = json.load(f)
|
|
print("✔ Calibration loaded.")
|
|
return data.get("zero_offset", 0), data.get("scale_factor", 1)
|
|
except Exception as e:
|
|
print("⚠ Calibration load error:", e)
|
|
return 0, 1
|
|
|
|
|
|
# ---------------------------------------------------------
|
|
# HX710B Class
|
|
# ---------------------------------------------------------
|
|
|
|
class HX710B:
|
|
def __init__(self, dout_pin, sck_pin):
|
|
self.dout = Pin(dout_pin, Pin.IN)
|
|
self.sck = Pin(sck_pin, Pin.OUT)
|
|
self.sck.value(0)
|
|
|
|
# Load previous calibration (or defaults)
|
|
self.zero_offset, self.scale_factor = load_calibration()
|
|
|
|
# -----------------------------------------------------
|
|
# Low-level raw ADC read
|
|
# -----------------------------------------------------
|
|
def read_raw(self):
|
|
"""Read the 24-bit raw ADC value."""
|
|
while self.dout.value():
|
|
pass # wait for data ready
|
|
|
|
count = 0
|
|
for _ in range(24):
|
|
self.sck.value(1)
|
|
count = (count << 1) | self.dout.value()
|
|
self.sck.value(0)
|
|
|
|
# 25th pulse to set gain for next reading
|
|
self.sck.value(1)
|
|
self.sck.value(0)
|
|
|
|
# Signed 24-bit conversion
|
|
if count & 0x800000:
|
|
count -= 0x1000000
|
|
|
|
return count
|
|
|
|
# -----------------------------------------------------
|
|
# Zero Calibration
|
|
# -----------------------------------------------------
|
|
def calibrate_zero(self, samples=20):
|
|
"""Measure 0 kPa and determine zero offset."""
|
|
total = 0
|
|
for _ in range(samples):
|
|
total += self.read_raw()
|
|
time.sleep_ms(5)
|
|
|
|
self.zero_offset = total / samples
|
|
save_calibration(self.zero_offset, self.scale_factor)
|
|
|
|
print("✔ Zero calibrated:", self.zero_offset)
|
|
return self.zero_offset
|
|
|
|
# -----------------------------------------------------
|
|
# Full-scale / Known Pressure Calibration
|
|
# -----------------------------------------------------
|
|
def calibrate_full(self, known_kpa, samples=20):
|
|
"""Measure raw ADC at known pressure and compute scaling."""
|
|
total = 0
|
|
for _ in range(samples):
|
|
total += self.read_raw()
|
|
time.sleep_ms(5)
|
|
|
|
raw_avg = total / samples
|
|
self.scale_factor = known_kpa / (raw_avg - self.zero_offset)
|
|
|
|
save_calibration(self.zero_offset, self.scale_factor)
|
|
|
|
print("✔ Scale calibrated:", self.scale_factor)
|
|
return self.scale_factor
|
|
|
|
# -----------------------------------------------------
|
|
# Convert raw → kPa using saved calibration
|
|
# -----------------------------------------------------
|
|
def read_kpa(self):
|
|
raw = self.read_raw()
|
|
return (raw - self.zero_offset) * self.scale_factor
|