From ebba98ef162ec35f7ae8e4abf570202d72eaad27 Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Mon, 21 Apr 2025 00:43:50 +0200
Subject: [PATCH] si7021: honour PRESENT flag, added GetValue

---
 avr/modules/si7021/main.asm | 50 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/avr/modules/si7021/main.asm b/avr/modules/si7021/main.asm
index 0ccc96e..8f146c8 100644
--- a/avr/modules/si7021/main.asm
+++ b/avr/modules/si7021/main.asm
@@ -1,5 +1,5 @@
 ; ***************************************************************************
-; copyright   : (C) 2023 by Martin Preuss
+; copyright   : (C) 2025 by Martin Preuss
 ; email       : martin@libchipcard.de
 ;
 ; ***************************************************************************
@@ -12,6 +12,8 @@
 ; ***************************************************************************
 ; defines
 
+.equ SI7021_FLAGS_PRESENT_BIT  = 7
+
 .equ SI7021_FLAGS_PRESENT      = 0x80
 .equ SI7021_FLAGS_TEMP_VALID   = 0x40
 .equ SI7021_FLAGS_HUM_VALID    = 0x20
@@ -19,6 +21,10 @@
 .equ SI7021_FLAGS_ERROR_MASK   = 0x07
 
 
+.equ SI7021_VALUE_TEMP         = 0x01
+.equ SI7021_VALUE_HUMIDITY     = 0x02
+
+
 ; ***************************************************************************
 ; data
 
@@ -105,6 +111,8 @@ SI7021_OnTimer:
   push r15
     cli
     lds r17, si7021Flags
+    sbrs r17, SI7021_FLAGS_PRESENT_BIT  ; investigate PRESENT BIT
+      rjmp SI7021_OnTimer_error         ; jmp if PRESENT bit clear
     mov r16, r17
     andi r16, SI7021_FLAGS_LASTWASTEMP
     brne SI7021_OnTimer_hum
@@ -444,6 +452,46 @@ si7021Muls16x16_32_done:
 
 
 
+; ---------------------------------------------------------------------------
+; @routine SI7021_GetValue @global
+;
+; @param   R16     value to get (SI7021_VALUE_TEMP, SI7021_VALUE_HUMIDITY)
+; @return  CFLAG   set if value available, cleared otherwise
+; @return  R19:R18 value
+; @return  R21:R20 denom (e.g. 100, meaning value must be divided by 100)
+; @clobbers R16
+
+SI7021_GetValue:
+  cpi r16, SI7021_VALUE_TEMP
+  breq SI7021_GetValue_temp
+  cpi r16, SI7021_VALUE_HUMIDITY
+  breq SI7021_GetValue_hum
+SI7021_GetValue_clcRet:
+  clc
+  ret
+SI7021_GetValue_temp:
+  lds r16, si7021Flags
+  andi r16, SI7021_FLAGS_TEMP_VALID
+  breq SI7021_GetValue_clcRet
+  lds r18, si7021LastTemp            ; value
+  lds r19, si7021LastTemp+1
+  ldi r20, 100                       ; denominator
+  rjmp SI7021_GetValue_finishValue
+SI7021_GetValue_hum:
+  lds r16, si7021Flags
+  andi r16, SI7021_FLAGS_HUM_VALID
+  breq SI7021_GetValue_clcRet
+  lds r18, si7021LastHumidity        ; value
+  lds r19, si7021LastHumidity+1
+  ldi r20, 1                         ; denominator
+SI7021_GetValue_finishValue:
+  clr r21
+  sec
+  ret
+; @end
+  
+
+
 
 SI7021_SendTemp:
   lds r16, si7021Flags