diff --git a/firmware/ch32x035-usb-device-compositekm-c/keyboard/CMakeLists.txt b/firmware/ch32x035-usb-device-compositekm-c/keyboard/CMakeLists.txt
index 728945568..23686bcf7 100644
--- a/firmware/ch32x035-usb-device-compositekm-c/keyboard/CMakeLists.txt
+++ b/firmware/ch32x035-usb-device-compositekm-c/keyboard/CMakeLists.txt
@@ -8,8 +8,10 @@ target_sources(keyboard PUBLIC
     ${CMAKE_CURRENT_SOURCE_DIR}/keyboard_split.c
     ${CMAKE_CURRENT_SOURCE_DIR}/keyboard_split_rx_dma.c
     ${CMAKE_CURRENT_SOURCE_DIR}/keyboard_split_tx_dma.c
+    ${CMAKE_CURRENT_SOURCE_DIR}/keyboard_touchkey.c
     ${CMAKE_CURRENT_SOURCE_DIR}/matrix/col_to_row.c
     ${CMAKE_CURRENT_SOURCE_DIR}/matrix/row_to_col.c
+    ${CMAKE_CURRENT_SOURCE_DIR}/matrix/touchkey_mutual.c
 )
 
 target_include_directories(keyboard INTERFACE ${CMAKE_CURRENT_BINARY_DIR})
diff --git a/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_gpio.c b/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_gpio.c
index 09261968f..eb894a55c 100644
--- a/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_gpio.c
+++ b/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_gpio.c
@@ -4,11 +4,6 @@
 
 GPIO_TypeDef *const GPIO_PORTS[] = {GPIOA, GPIOB, GPIOC};
 
-typedef struct {
-  GPIO_TypeDef *port;
-  uint32_t pin;
-} ch32x_gpio_t;
-
 ch32x_gpio_t to_ch32x_gpio(keyboard_gpio_t gpio_source) {
   ch32x_gpio_t result = {
       .port = GPIO_PORTS[gpio_source.port],
diff --git a/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_gpio.h b/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_gpio.h
index 186aafc8a..f214b3c67 100644
--- a/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_gpio.h
+++ b/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_gpio.h
@@ -3,6 +3,8 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+#include "ch32x035.h"
+
 typedef struct {
   // Port Source
   uint8_t port;
@@ -10,6 +12,13 @@ typedef struct {
   uint8_t pin;
 } keyboard_gpio_t;
 
+typedef struct {
+  GPIO_TypeDef *port;
+  uint32_t pin;
+} ch32x_gpio_t;
+
+ch32x_gpio_t to_ch32x_gpio(keyboard_gpio_t gpio_source);
+
 void keyboard_gpio_configure_ipu(keyboard_gpio_t gpio);
 void keyboard_gpio_configure_output(keyboard_gpio_t gpio);
 
diff --git a/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_touchkey.c b/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_touchkey.c
new file mode 100644
index 000000000..3c2eab243
--- /dev/null
+++ b/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_touchkey.c
@@ -0,0 +1,52 @@
+#include "keyboard_touchkey.h"
+
+#include "ch32x035_adc.h"
+#include "ch32x035_gpio.h"
+#include "ch32x035_rcc.h"
+
+#include "keyboard_gpio.h"
+
+void keyboard_touchkey_configure_drive(keyboard_gpio_t gpio_source) {
+  keyboard_gpio_configure_output(gpio_source);
+  keyboard_gpio_reset(gpio_source);
+}
+
+void keyboard_touchkey_configure_sense(keyboard_gpio_t gpio_source) {
+  ch32x_gpio_t gpio = to_ch32x_gpio(gpio_source);
+  GPIO_InitTypeDef gpio_init_value = {
+      .GPIO_Pin = gpio.pin,
+      .GPIO_Mode = GPIO_Mode_AIN,
+  };
+  GPIO_Init(gpio.port, &gpio_init_value);
+}
+
+void keyboard_touchkey_init(void) {
+  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
+
+  ADC_CLKConfig(ADC1, ADC_CLK_Div6);
+
+  ADC_InitTypeDef adc_init_value = {
+      .ADC_Mode = ADC_Mode_Independent,
+      .ADC_ScanConvMode = DISABLE,
+      .ADC_ContinuousConvMode = DISABLE,
+      .ADC_ExternalTrigConv = ADC_ExternalTrigConv_None,
+      .ADC_DataAlign = ADC_DataAlign_Right,
+      .ADC_NbrOfChannel = 1,
+  };
+  ADC_Init(ADC1, &adc_init_value);
+
+  ADC_Cmd(ADC1, ENABLE);
+
+  TKey1->CTLR1 |= ADC_TKENABLE;
+}
+
+uint16_t keyboard_touchkey_read(uint8_t ch) {
+  // TODO: allow configuration
+  ADC_RegularChannelConfig(ADC1, ch, 1, ADC_SampleTime_11Cycles);
+  TKey1->IDATAR1 = 0xFF; // Charging Time
+  TKey1->RDATAR = 0xFF;  // Discharging Time; start read
+  while (!ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC))
+    ;
+
+  return (uint16_t)TKey1->RDATAR;
+}
diff --git a/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_touchkey.h b/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_touchkey.h
new file mode 100644
index 000000000..75610dd70
--- /dev/null
+++ b/firmware/ch32x035-usb-device-compositekm-c/keyboard/keyboard_touchkey.h
@@ -0,0 +1,9 @@
+#pragma once
+
+#include "keyboard_gpio.h"
+
+void keyboard_touchkey_configure_drive(keyboard_gpio_t gpio);
+void keyboard_touchkey_configure_sense(keyboard_gpio_t gpio);
+
+void keyboard_touchkey_init(void);
+uint16_t keyboard_touchkey_read(uint8_t ch);
diff --git a/firmware/ch32x035-usb-device-compositekm-c/keyboard/matrix/touchkey_mutual.c b/firmware/ch32x035-usb-device-compositekm-c/keyboard/matrix/touchkey_mutual.c
new file mode 100644
index 000000000..143a481c7
--- /dev/null
+++ b/firmware/ch32x035-usb-device-compositekm-c/keyboard/matrix/touchkey_mutual.c
@@ -0,0 +1,143 @@
+#ifdef KEYBOARD_MATRIX_IMPL_TOUCHKEY_MUTUAL
+#include "debug.h"
+
+#include "ch32x035_rcc.h"
+
+#include "keyboard_gpio.h"
+#include "keyboard_matrix.h"
+#include "keyboard_touchkey.h"
+
+uint16_t tkey_baselines[KEYBOARD_MATRIX_KEY_COUNT] = {0};
+uint16_t tkey_readings[KEYBOARD_MATRIX_KEY_COUNT] = {0};
+
+// KLUDGE: hardcoded. Ideally, comes from codegen.
+// for board: ch32x-tc-2x4 rev2025.1
+uint8_t adc_channel_map[4] = {
+    // per col
+    4, // col 1
+    6, // col 2
+    8, // col 3
+    9, // col 4
+};
+
+void init_column(keyboard_gpio_t col) {
+  keyboard_touchkey_configure_sense(col);
+}
+
+void init_row(keyboard_gpio_t row) { keyboard_touchkey_configure_drive(row); }
+
+void keyboard_matrix_scan_raw(bool scan_buf[KEYBOARD_MATRIX_KEY_COUNT]);
+
+void keyboard_matrix_init(void) {
+  // NOTE: this implementation is for 'touchkeys' using mutual capacitance,
+  //  driving on rows, sensing on columns.
+
+  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);
+  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
+  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);
+
+  // Sense Cols
+  for (uint8_t i = 0; i < KEYBOARD_MATRIX_COL_COUNT; i++) {
+    init_column(keyboard_matrix_cols[i]);
+  }
+
+  // Drive Rows
+  for (uint8_t i = 0; i < KEYBOARD_MATRIX_ROW_COUNT; i++) {
+    init_row(keyboard_matrix_rows[i]);
+    keyboard_gpio_reset(keyboard_matrix_rows[i]);
+  }
+
+  keyboard_touchkey_init();
+
+  // Scan once to set ADC values
+  bool current_raw_scan[KEYBOARD_MATRIX_KEY_COUNT] = {false};
+  keyboard_matrix_scan_raw(current_raw_scan);
+}
+
+void discharge_pin(keyboard_gpio_t col) {
+  // Ensure col is discharged
+  keyboard_gpio_configure_output(col);
+  keyboard_gpio_reset(col);
+  Delay_Us(5);
+  keyboard_touchkey_configure_sense(col);
+}
+
+void keyboard_matrix_scan_column_for_row(
+    keyboard_matrix_coordinate_t index,
+    bool scan_buf[KEYBOARD_MATRIX_KEY_COUNT]) {
+  uint8_t column_index = index.column;
+  uint8_t row_index = index.row;
+  keyboard_gpio_t column = keyboard_matrix_cols[column_index];
+
+  discharge_pin(column);
+
+  uint16_t adc_value = keyboard_touchkey_read(adc_channel_map[column_index]);
+
+  uint8_t keymap_index = keymap_indices[row_index][column_index];
+
+  if (keymap_index >= 0) {
+    tkey_readings[keymap_index] = adc_value;
+
+    // Initialize baseline if not set
+    if (tkey_baselines[keymap_index] == 0) {
+      tkey_baselines[keymap_index] = adc_value;
+    }
+
+    uint16_t threshold = 150; // TODO: make configurable
+    if (adc_value < tkey_baselines[keymap_index] - threshold) {
+      scan_buf[keymap_index] = true;
+    } else {
+      scan_buf[keymap_index] = false;
+
+      // Update baseline
+      uint8_t n = 64;
+      tkey_baselines[keymap_index] =
+          (tkey_baselines[keymap_index] * (n - 1) / n) + (adc_value * 1 / n);
+    }
+  }
+}
+
+void keyboard_matrix_scan_row(uint8_t row_index,
+                              bool scan_buf[KEYBOARD_MATRIX_KEY_COUNT]) {
+  keyboard_gpio_t row = keyboard_matrix_rows[row_index];
+
+  keyboard_gpio_set(row);
+  Delay_Us(5);
+
+  for (uint8_t column_index = 0; column_index < KEYBOARD_MATRIX_COL_COUNT;
+       column_index++) {
+    keyboard_matrix_coordinate_t index = {.column = column_index,
+                                          .row = row_index};
+    keyboard_matrix_scan_column_for_row(index, scan_buf);
+  }
+
+  keyboard_gpio_reset(row);
+}
+
+void keyboard_matrix_scan_raw(bool scan_buf[KEYBOARD_MATRIX_KEY_COUNT]) {
+  static uint16_t counter = 0;
+
+  if ((++counter) > 1000) {
+    printf("base: \r\n %5d %5d\r\n %5d %5d\r\n", tkey_baselines[0],
+           tkey_baselines[1], tkey_baselines[2], tkey_baselines[3]);
+    printf("read: \r\n %5d %5d\r\n %5d %5d\r\n", tkey_readings[0],
+           tkey_readings[1], tkey_readings[2], tkey_readings[3]);
+    printf("delt: \r\n %5d %5d\r\n %5d %5d\r\n",
+           ((int32_t)(tkey_readings[0]) - (int32_t)(tkey_baselines[0])),
+           ((int32_t)(tkey_readings[1]) - (int32_t)(tkey_baselines[1])),
+           ((int32_t)(tkey_readings[2]) - (int32_t)(tkey_baselines[2])),
+           ((int32_t)(tkey_readings[3]) - (int32_t)(tkey_baselines[3])));
+    printf("\r\n");
+    counter = 0;
+  }
+
+  for (uint8_t row_index = 0; row_index < KEYBOARD_MATRIX_ROW_COUNT;
+       row_index++) {
+    keyboard_matrix_scan_row(row_index, scan_buf);
+  }
+}
+
+bool keyboard_matrix_is_sw_1_1_pressed() {
+  return false; // TBI
+}
+#endif
diff --git a/firmware/ch32x035-usb-device-compositekm-c/ncl/boards/ch32x-tc-2x4.ncl b/firmware/ch32x035-usb-device-compositekm-c/ncl/boards/ch32x-tc-2x4.ncl
new file mode 100644
index 000000000..7e977b107
--- /dev/null
+++ b/firmware/ch32x035-usb-device-compositekm-c/ncl/boards/ch32x-tc-2x4.ncl
@@ -0,0 +1,45 @@
+let C = import "keyboard/contracts.ncl" in
+
+{
+  gpio_pins | C.GpioPins,
+
+  board | C.Board = {
+    matrix =
+      let p = gpio_pins in
+      {
+        # Sense columns
+        cols = [p.A4, p.A6, p.A7, p.B1],
+        # Drive rows
+        rows = [
+            p.A0,
+            p.A5,
+        ],
+        key_count = 8,
+
+        implementation = "touchkey_mutual",
+      },
+
+    keymap_index_for_key = fun { column_index | Number, row_index | Number, .. } =>
+      let [
+        k00, k01, k02, k03,
+        k04, k05, k06, k07,
+      ] = std.array.generate (fun i => 'Key i) matrix.key_count in
+      let NO = 'NoKey in
+      let matrix = [
+        [k00, k01, k02, k03],
+        [k04, k05, k06, k07],
+      ]
+      in
+      matrix
+      |> std.array.at row_index
+      |> std.array.at column_index,
+
+    led = {
+      enabled = true,
+      pin = gpio_pins.A3,
+    },
+
+    # TX4 available if Col3 not used.
+    debug.tx = 1,
+  },
+}