From 6f16e7fdc3ab4f64f70adca3ace578c8c78012b4 Mon Sep 17 00:00:00 2001
From: Alex van de Sandt <me@alexvds.com>
Date: Thu, 7 May 2026 13:16:14 -0500
Subject: [PATCH] Catch error responses

---
 src/codec.rs                               | 28 ++++++++++++++++++++++
 src/command/bc125at/battery_charge_time.rs |  2 +-
 src/command/bc125at/lcd_contrast.rs        |  2 +-
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/src/codec.rs b/src/codec.rs
index 558a51c..3660680 100644
--- a/src/codec.rs
+++ b/src/codec.rs
@@ -84,6 +84,12 @@ pub enum DecoderError {
     #[error("malformed response")]
     Malformed,
 
+    #[error("command must be executed in program mode")]
+    NotAcceptable,
+
+    #[error("command format error or invalid value")]
+    ErrorResponse,
+
     #[error(transparent)]
     DelimiterError(#[from] AnyDelimiterCodecError),
 
@@ -110,6 +116,14 @@ impl Decoder for Codec {
 
         let raw_values = all_fields.collect::<Vec<_>>();
 
+        if raw_values.len() == 1 {
+            match raw_values[0].as_ref() {
+                b"NG" => return Err(DecoderError::NotAcceptable),
+                b"ERR" => return Err(DecoderError::ErrorResponse),
+                _ => {}
+            }
+        }
+
         Ok(Some(RawResponse { cmd, raw_values }))
     }
 }
@@ -219,6 +233,20 @@ mod tests {
             assert_matches!(err, DecoderError::Malformed);
         }
 
+        #[test]
+        fn not_acceptable_response() {
+            let err = decode(b"CMD,NG\r").unwrap_err();
+
+            assert_matches!(err, DecoderError::NotAcceptable);
+        }
+
+        #[test]
+        fn error_response() {
+            let err = decode(b"CMD,ERR\r").unwrap_err();
+
+            assert_matches!(err, DecoderError::ErrorResponse);
+        }
+
         #[test]
         fn delimiter_error() {
             let mut codec = Codec::new();
diff --git a/src/command/bc125at/battery_charge_time.rs b/src/command/bc125at/battery_charge_time.rs
index 4eaffa8..2d87bed 100644
--- a/src/command/bc125at/battery_charge_time.rs
+++ b/src/command/bc125at/battery_charge_time.rs
@@ -1,6 +1,6 @@
 use crate::command::{OkResponse, command, range_param, range_response};
 
-range_param!(BatteryChargeTime(0..=16): u8);
+range_param!(BatteryChargeTime(1..=16): u8);
 range_response!(BatteryChargeTime => BatteryChargeTimeError : InvalidBatteryChargeTime("volume must be between [1..16], got `{0}`"));
 
 command!(b"BSV": GetBatteryInfo => BatteryChargeTime);
diff --git a/src/command/bc125at/lcd_contrast.rs b/src/command/bc125at/lcd_contrast.rs
index 80ff740..f40a74e 100644
--- a/src/command/bc125at/lcd_contrast.rs
+++ b/src/command/bc125at/lcd_contrast.rs
@@ -1,6 +1,6 @@
 use crate::command::{OkResponse, command, range_param, range_response};
 
-range_param!(LcdContrast(1..=15): u8);
+range_param!(LcdContrast(0..=15): u8);
 range_response!(LcdContrast => LcdContrastError : InvalidLcdContrast("LCD contrast must be between [1..15], got `{0}`"));
 
 command!(b"CNT": GetLcdContrast => LcdContrast);
-- 
2.51.2