From 62dec35e4dd47e22b951eab86328b3632f303e57 Mon Sep 17 00:00:00 2001
From: Jeph <4734254+strongbutgood@users.noreply.github.com>
Date: Tue, 15 Mar 2022 23:40:58 +1300
Subject: [PATCH 1/3] Ensure calibration registers loaded before read

---
 bmp280.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/bmp280.py b/bmp280.py
index 07f8d3d..0220251 100644
--- a/bmp280.py
+++ b/bmp280.py
@@ -90,6 +90,8 @@ def __init__(self, i2c_bus, addr=0x76, use_case=BMP280_CASE_HANDHELD_DYN):
         self._bmp_i2c = i2c_bus
         self._i2c_addr = addr
 
+        while self.is_updating:
+            pass
         # read calibration data
         # < little-endian
         # H unsigned short

From 99c5c6e43b79322b334765f1936040a5204d1d70 Mon Sep 17 00:00:00 2001
From: Jeph <4734254+strongbutgood@users.noreply.github.com>
Date: Wed, 16 Mar 2022 11:15:04 +1300
Subject: [PATCH 2/3] Separate calibration data read

Add confirmation that calibration data is read.
Refuse to read calibration data while registers are written from NVM.
---
 bmp280.py | 46 ++++++++++++++++++++++++++++------------------
 1 file changed, 28 insertions(+), 18 deletions(-)

diff --git a/bmp280.py b/bmp280.py
index 0220251..3c91626 100644
--- a/bmp280.py
+++ b/bmp280.py
@@ -90,24 +90,11 @@ def __init__(self, i2c_bus, addr=0x76, use_case=BMP280_CASE_HANDHELD_DYN):
         self._bmp_i2c = i2c_bus
         self._i2c_addr = addr
 
-        while self.is_updating:
-            pass
-        # read calibration data
-        # < little-endian
-        # H unsigned short
-        # h signed short
-        self._T1 = unp('<H', self._read(0x88, 2))[0]
-        self._T2 = unp('<h', self._read(0x8A, 2))[0]
-        self._T3 = unp('<h', self._read(0x8C, 2))[0]
-        self._P1 = unp('<H', self._read(0x8E, 2))[0]
-        self._P2 = unp('<h', self._read(0x90, 2))[0]
-        self._P3 = unp('<h', self._read(0x92, 2))[0]
-        self._P4 = unp('<h', self._read(0x94, 2))[0]
-        self._P5 = unp('<h', self._read(0x96, 2))[0]
-        self._P6 = unp('<h', self._read(0x98, 2))[0]
-        self._P7 = unp('<h', self._read(0x9A, 2))[0]
-        self._P8 = unp('<h', self._read(0x9C, 2))[0]
-        self._P9 = unp('<h', self._read(0x9E, 2))[0]
+        self._T1 = self._T2 = self._T3 = \
+            self._P1 = self._P2 = self._P3 = \
+            self._P4 = self._P5 = self._P6 = \
+            self._P7 = self._P8 = self._P9 = 0
+        self.calibrate()
 
         # output raw
         self._t_raw = 0
@@ -144,6 +131,29 @@ def _gauge(self):
         self._t = 0
         self._p = 0
 
+    def calibrate(self):
+        if self._T1 != 0:
+            return True
+        if self.is_updating:
+            return False
+        # read calibration data
+        # < little-endian
+        # H unsigned short
+        # h signed short
+        self._T1 = unp('<H', self._read(0x88, 2))[0]
+        self._T2 = unp('<h', self._read(0x8A, 2))[0]
+        self._T3 = unp('<h', self._read(0x8C, 2))[0]
+        self._P1 = unp('<H', self._read(0x8E, 2))[0]
+        self._P2 = unp('<h', self._read(0x90, 2))[0]
+        self._P3 = unp('<h', self._read(0x92, 2))[0]
+        self._P4 = unp('<h', self._read(0x94, 2))[0]
+        self._P5 = unp('<h', self._read(0x96, 2))[0]
+        self._P6 = unp('<h', self._read(0x98, 2))[0]
+        self._P7 = unp('<h', self._read(0x9A, 2))[0]
+        self._P8 = unp('<h', self._read(0x9C, 2))[0]
+        self._P9 = unp('<h', self._read(0x9E, 2))[0]
+        return True
+        
     def reset(self):
         self._write(_BMP280_REGISTER_RESET, 0xB6)
 

From ffa6d300882f0745f319a3ccebcb979542809caa Mon Sep 17 00:00:00 2001
From: Jeph <4734254+strongbutgood@users.noreply.github.com>
Date: Sun, 20 Mar 2022 23:47:57 +1300
Subject: [PATCH 3/3] Remove conditions from calibrate method

---
 bmp280.py | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/bmp280.py b/bmp280.py
index 3c91626..1dd158d 100644
--- a/bmp280.py
+++ b/bmp280.py
@@ -132,10 +132,6 @@ def _gauge(self):
         self._p = 0
 
     def calibrate(self):
-        if self._T1 != 0:
-            return True
-        if self.is_updating:
-            return False
         # read calibration data
         # < little-endian
         # H unsigned short
@@ -152,7 +148,7 @@ def calibrate(self):
         self._P7 = unp('<h', self._read(0x9A, 2))[0]
         self._P8 = unp('<h', self._read(0x9C, 2))[0]
         self._P9 = unp('<h', self._read(0x9E, 2))[0]
-        return True
+        return self._T1 != 0
         
     def reset(self):
         self._write(_BMP280_REGISTER_RESET, 0xB6)