drivers/onewire/ds18x20: Fix negative temperature calc for DS18B20.

b2611d6b · syndycat · Damien George · 044f96c3 · b2611d6b
Commit b2611d6b authored Jan 07, 2017 by syndycat Committed by Damien George Jan 08, 2017
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drivers/onewire/ds18x20.py drivers/onewire/ds18x20.py +4 -1

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--- a/drivers/onewire/ds18x20.py
+++ b/drivers/onewire/ds18x20.py
@@ -93,6 +93,9 @@ class DS18X20(object):
            temp = temp_read - 0.25 + (count_per_c - count_remain) / count_per_c
            return temp
        elif rom0 == 0x28:
-            return (temp_msb << 8 | temp_lsb) / 16
+            temp = (temp_msb << 8 | temp_lsb) / 16
+            if (temp_msb & 0xf8) == 0xf8: # for negative temperature
+                temp -= 0x1000
+            return temp
        else:
            assert False