From 03aaa66f8e9c9cec01588e20a4797d7c8926af80 Mon Sep 17 00:00:00 2001
From: jsmarion <jsmarion@users.noreply.github.com>
Date: Wed, 3 Dec 2025 14:35:14 -0500
Subject: [PATCH] [cst816] Fix CST826 & CST836 (#12260)

Co-authored-by: Jonathan Swoboda <154711427+swoboda1337@users.noreply.github.com>
---
 .../cst816/touchscreen/cst816_touchscreen.cpp | 64 ++++++++++++-------
 .../cst816/touchscreen/cst816_touchscreen.h   |  2 +
 2 files changed, 42 insertions(+), 24 deletions(-)

diff --git a/esphome/components/cst816/touchscreen/cst816_touchscreen.cpp b/esphome/components/cst816/touchscreen/cst816_touchscreen.cpp
index f6280a75a1..5be93692c0 100644
--- a/esphome/components/cst816/touchscreen/cst816_touchscreen.cpp
+++ b/esphome/components/cst816/touchscreen/cst816_touchscreen.cpp
@@ -9,27 +9,40 @@ void CST816Touchscreen::continue_setup_() {
     this->interrupt_pin_->setup();
     this->attach_interrupt_(this->interrupt_pin_, gpio::INTERRUPT_FALLING_EDGE);
   }
-  if (this->read_byte(REG_CHIP_ID, &this->chip_id_)) {
-    switch (this->chip_id_) {
-      case CST820_CHIP_ID:
-      case CST826_CHIP_ID:
-      case CST716_CHIP_ID:
-      case CST816S_CHIP_ID:
-      case CST816D_CHIP_ID:
-      case CST816T_CHIP_ID:
-        break;
-      default:
+
+  if (!this->read_byte(REG_CHIP_ID, &this->chip_id_) && !this->skip_probe_) {
+    this->status_set_error(LOG_STR("Failed to read chip ID"));
+    this->mark_failed();
+    return;
+  }
+
+  // CST826/CST836 return 0 for chip ID, need to read from factory ID register
+  if (this->chip_id_ == 0) {
+    if (!this->read_byte(REG_FACTORY_ID, &this->chip_id_) && !this->skip_probe_) {
+      this->status_set_error(LOG_STR("Failed to read chip ID"));
+      this->mark_failed();
+      return;
+    }
+  }
+
+  switch (this->chip_id_) {
+    case CST716_CHIP_ID:
+    case CST816S_CHIP_ID:
+    case CST816D_CHIP_ID:
+    case CST816T_CHIP_ID:
+    case CST820_CHIP_ID:
+    case CST826_CHIP_ID:
+    case CST836_CHIP_ID:
+      break;
+    default:
+      if (!this->skip_probe_) {
         ESP_LOGE(TAG, "Unknown chip ID: 0x%02X", this->chip_id_);
         this->status_set_error(LOG_STR("Unknown chip ID"));
         this->mark_failed();
         return;
-    }
-    this->write_byte(REG_IRQ_CTL, IRQ_EN_MOTION);
-  } else if (!this->skip_probe_) {
-    this->status_set_error(LOG_STR("Failed to read chip id"));
-    this->mark_failed();
-    return;
+      }
   }
+  this->write_byte(REG_IRQ_CTL, IRQ_EN_MOTION);
   if (this->x_raw_max_ == this->x_raw_min_) {
     this->x_raw_max_ = this->display_->get_native_width();
   }
@@ -80,11 +93,8 @@ void CST816Touchscreen::dump_config() {
                 this->x_raw_min_, this->x_raw_max_, this->y_raw_min_, this->y_raw_max_);
   const char *name;
   switch (this->chip_id_) {
-    case CST820_CHIP_ID:
-      name = "CST820";
-      break;
-    case CST826_CHIP_ID:
-      name = "CST826";
+    case CST716_CHIP_ID:
+      name = "CST716";
       break;
     case CST816S_CHIP_ID:
       name = "CST816S";
@@ -92,12 +102,18 @@ void CST816Touchscreen::dump_config() {
     case CST816D_CHIP_ID:
       name = "CST816D";
       break;
-    case CST716_CHIP_ID:
-      name = "CST716";
-      break;
     case CST816T_CHIP_ID:
       name = "CST816T";
       break;
+    case CST820_CHIP_ID:
+      name = "CST820";
+      break;
+    case CST826_CHIP_ID:
+      name = "CST826";
+      break;
+    case CST836_CHIP_ID:
+      name = "CST836";
+      break;
     default:
       name = "Unknown";
       break;
diff --git a/esphome/components/cst816/touchscreen/cst816_touchscreen.h b/esphome/components/cst816/touchscreen/cst816_touchscreen.h
index 99ea085e37..99b93d8342 100644
--- a/esphome/components/cst816/touchscreen/cst816_touchscreen.h
+++ b/esphome/components/cst816/touchscreen/cst816_touchscreen.h
@@ -19,12 +19,14 @@ static const uint8_t REG_YPOS_HIGH = 0x05;
 static const uint8_t REG_YPOS_LOW = 0x06;
 static const uint8_t REG_DIS_AUTOSLEEP = 0xFE;
 static const uint8_t REG_CHIP_ID = 0xA7;
+static const uint8_t REG_FACTORY_ID = 0xAA;
 static const uint8_t REG_FW_VERSION = 0xA9;
 static const uint8_t REG_SLEEP = 0xE5;
 static const uint8_t REG_IRQ_CTL = 0xFA;
 static const uint8_t IRQ_EN_MOTION = 0x70;
 
 static const uint8_t CST826_CHIP_ID = 0x11;
+static const uint8_t CST836_CHIP_ID = 0x13;
 static const uint8_t CST820_CHIP_ID = 0xB7;
 static const uint8_t CST816S_CHIP_ID = 0xB4;
 static const uint8_t CST816D_CHIP_ID = 0xB6;