From 94c2224b00ff5e2de69fb54adff7cb2cd4b7ec9d Mon Sep 17 00:00:00 2001
From: Stefan A <stefan@alfredsson.se>
Date: Sun, 26 May 2024 12:51:58 +0200
Subject: [PATCH] Bugfix for sign conversion

HDLC 0x10 is a signed 2-byte integer, but was put in 32 bit signed variable so the sign was lost for negative values (when current is negative / power is exported to the grid)
---
 p1reader.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/p1reader.h b/p1reader.h
index fff6854..ca74c48 100644
--- a/p1reader.h
+++ b/p1reader.h
@@ -387,7 +387,9 @@ class P1ReaderHDLC : public P1Reader {
         Serial.readBytes(buffer, 2); 
         //value = buffer[0] | buffer[1] << 8; // 
         is_signed = true;
-        value = buffer[1] | buffer[0] << 8;
+        // value is 32 bit, so we must use 16 bit temp variable to get sign correct (casting was unsuccessful)
+        int16_t temp = buffer[1] | buffer[0] << 8;
+        value = temp;
         //ESP_LOGD("hdlc", "(Signed) Value of value is %d", value);
       } else if (tag == 0x12) {
         Serial.readBytes(buffer, 2); 
@@ -522,4 +524,4 @@ class P1ReaderHDLC : public P1Reader {
         }
       }
     }
-};
\ No newline at end of file
+};