From 03f794b2533cfe16088de1cd3e642304d7ac61b4 Mon Sep 17 00:00:00 2001
From: Martin Preuss <martin@aquamaniac.de>
Date: Mon, 10 Nov 2025 15:55:31 +0100
Subject: [PATCH] xpt2046: reading values works.

---
 avr/modules/lcd2/xpt2046/main.asm | 80 ++++++++++++++++++++-----------
 1 file changed, 51 insertions(+), 29 deletions(-)

diff --git a/avr/modules/lcd2/xpt2046/main.asm b/avr/modules/lcd2/xpt2046/main.asm
index 070e93a..10e80d6 100644
--- a/avr/modules/lcd2/xpt2046/main.asm
+++ b/avr/modules/lcd2/xpt2046/main.asm
@@ -16,9 +16,9 @@
 ; ***************************************************************************
 ; defines
 
-.equ XPT2046_SPIMODE = (1<<SPIHW_MODE_SPEED0_BIT) | \
-                       (1<<SPIHW_MODE_SPEED1_BIT) | \
-                       (0<<SPIHW_MODE_DOUBLESPEED_BIT) | \
+.equ XPT2046_SPIMODE = (0<<SPIHW_MODE_SPEED0_BIT) | \
+                       (0<<SPIHW_MODE_SPEED1_BIT) | \
+                       (1<<SPIHW_MODE_DOUBLESPEED_BIT) | \
                        (0<<SPIHW_MODE_DATAORDER_BIT) | \
                        (0<<SPIHW_MODE_CPOL_BIT) | \
                        (0<<SPIHW_MODE_CPHA_BIT)
@@ -30,7 +30,7 @@
 .equ XPT2046_CMD_READ_Z2 = 0xc1
 
 .equ XPT2046_AVERAGE     = 2
-.equ XPT2046_Z_THRESHOLD = 500
+.equ XPT2046_Z_THRESHOLD = 50
 .equ XPT2046_TIMER_VALUE = 3   ; every 300ms
 
 .equ XPT2046_FLAGS_PRESSED_BIT  = 7
@@ -127,22 +127,35 @@ xpt2046UpdateValues:
     lds r23, xpt2046Flags
     rcall xpt2046BeginSpi          ; (R16, R17)
 
-#if 0
-    ldi r16, XPT2046_CMD_READ_X
+;    rcall xpt2046UpdateZ
+
+    ldi r16, XPT2046_CMD_READ_Z1
     rcall xpt2046SendCommandRecv12Bit  ; (R16)
-    sts xpt2046CurrentX, r18
-    sts xpt2046CurrentX+1, r19
-    lds r24, xpt2046CurrentY
-    lds r25, xpt2046CurrentY+1
-    adiw r25:r24, 1
-    sts xpt2046CurrentY, r24
-    sts xpt2046CurrentY+1, r25
-#else
+    sts xpt2046CurrentZ, r18
+    sts xpt2046CurrentZ+1, r19
+    ldi r16, LOW(XPT2046_Z_THRESHOLD)
+    ldi r17, HIGH(XPT2046_Z_THRESHOLD)
+    sub r18, r16
+    sbc r19, r17
+    brcc xpt2046UpdateValues_aboveThreshold
+    cbr r23, (1<<XPT2046_FLAGS_PRESSED_BIT) ; Z below threshold, not pressed
+    rjmp xpt2046UpdateValues_checkPressChg
+xpt2046UpdateValues_aboveThreshold:
+    ori r23, (1<<XPT2046_FLAGS_PRESSED_BIT)
+xpt2046UpdateValues_checkPressChg:
+    eor r16, r23
+    andi r16, (1<<XPT2046_FLAGS_PRESSED_BIT)
+    breq xpt2046UpdateValues_checkPress
+    ori r23, (1<<XPT2046_FLAGS_CHGPRESS_BIT)
+xpt2046UpdateValues_checkPress:
+    mov r16, r23
+    andi r16, (1<<XPT2046_FLAGS_PRESSED_BIT) ; only read coords if pressed
+    breq xpt2046UpdateValues_storeFlags
+
     rcall xpt2046UpdateX
     rcall xpt2046UpdateY
-    rcall xpt2046UpdateZ
-#endif
 
+xpt2046UpdateValues_storeFlags:
     sts xpt2046Flags, r23
     rcall xpt2046EndSpi            ; (R16, R17)
 
@@ -215,21 +228,13 @@ xpt2046UpdateY_ret:
 xpt2046UpdateZ:
   ldi r16, XPT2046_CMD_READ_Z1
   rcall xpt2046SendCommandRecv12Bit  ; (R16)
-  ldi r24, LOW(4095)
-  ldi r25, HIGH(4095)
-  add r24, r18
-  adc r25, r19
-  ldi r16, XPT2046_CMD_READ_Z2
-  rcall xpt2046SendCommandRecv12Bit  ; (R16)
-  sub r24, r18
-  sbc r25, r19
-  sts xpt2046CurrentZ, r24
-  sts xpt2046CurrentZ+1, r25
+  sts xpt2046CurrentZ, r18
+  sts xpt2046CurrentZ+1, r19
   
   ldi r16, LOW(XPT2046_Z_THRESHOLD)
   ldi r17, HIGH(XPT2046_Z_THRESHOLD)
-  sub r24, r16
-  sbc r25, r17
+  sub r18, r16
+  sbc r19, r17
   mov r16, r23
   brcs xpt2046UpdateZ_overThreshold
   cbr r23, (1<<XPT2046_FLAGS_PRESSED_BIT) ; Z below threshold, not pressed
@@ -370,7 +375,24 @@ xpt2046SendCommandRecv16Bit:
   clr r16
   rcall SPIHW_MasterTransfer              ; (R16)
   mov r18, r16
-  sbi SPIHW_SS_OUTPUT, SPIHW_SS_PIN       ; SS low
+  sbi SPIHW_SS_OUTPUT, SPIHW_SS_PIN       ; SS high
+  ret
+; @end
+
+
+
+; ---------------------------------------------------------------------------
+; @routine xpt2046SendCommandRecv8Bit
+;
+; @param r16 command
+; @return r16 data
+; @clobbers r16
+
+xpt2046SendCommandRecv8Bit:
+  cbi SPIHW_SS_OUTPUT, SPIHW_SS_PIN       ; SS low
+  rcall SPIHW_MasterTransfer              ; (R16)
+  mov r18, r16
+  sbi SPIHW_SS_OUTPUT, SPIHW_SS_PIN       ; SS high
   ret
 ; @end