diff --git a/nametag8_CH592/user/comm/soft_i2c_slave.c b/nametag8_CH592/user/comm/soft_i2c_slave.c
index d063670..039262a 100644
--- a/nametag8_CH592/user/comm/soft_i2c_slave.c
+++ b/nametag8_CH592/user/comm/soft_i2c_slave.c
@@ -16,8 +16,8 @@
 
 
 
-#define I2CSS_ERR_TIMEOUT   3       // timeout in bit-times before i2c slave releases control
-#define I2CSS_IDLE_TIMEOUT  4       // idle timeout required in bit-times before i2c slave can be addressed again
+#define I2CSS_ERR_TIMEOUT   10      // timeout in bit-times before i2c slave releases control
+#define I2CSS_IDLE_TIMEOUT  3       // idle timeout required in bit-times before i2c slave can be addressed again
 
 
 // todo: use with struct instead of hard-coding to allow for multiple slaves, but make it fast too
@@ -84,8 +84,8 @@ static inline int8_t i2css_ack(uint16_t bit_time)
 
     SDA_OUTLO();
 
-    if (i2css_wait_for_scl_hi()) return I2CSS_ACK_ERROR;
-    ret = i2css_wait_for_scl_lo();
+    if (i2css_wait_for_scl_hi()) ret = I2CSS_ACK_ERROR;
+    else ret = i2css_wait_for_scl_lo();
 
     SDA_IN_HI();
 
@@ -308,8 +308,19 @@ int8_t i2css_blocking(struct I2CSoftSlave *slave)
 __HIGH_CODE
 int8_t i2css_start(struct I2CSoftSlave *slave)
 {
+    int8_t ret;
     uint8_t scl;
 
+    if (idle_timeout) {
+        // we're still waiting for bus idle time before we reply to requests
+        // this will now reset the timeout
+        if (idle_timeout < I2CSS_IDLE_TIMEOUT) {
+            idle_timeout = I2CSS_IDLE_TIMEOUT;
+        }
+
+        return I2CSS_IN_TIMEOUT;
+    }
+
     // idle our clock and check for start/stop
     SCL_IN_HI();
     scl = SCL_GET();
@@ -317,14 +328,25 @@ int8_t i2css_start(struct I2CSoftSlave *slave)
     // module will use this bit time for this communication
     bit_time = slave->bit_time;
 
-    // ensure SDA pin will go low when set as an output
+    // if SCL is high, this may be a start condition.
+    if (scl) {
+        ret = i2css_blocking(slave);
+    } else ret = I2CSS_BUS_BUSY;
+
+    R16_PA_INT_IF = 1 << SDA_PIN;
+
+    return ret;
+}
+
+void i2css_init()
+{
+    // configure GPIO
+    SCL_IN_HI();
+    SCL_SET_LO();
+
+    SDA_IN_HI();
     SDA_SET_LO();
 
-    // if SCL is high, this should be a start condition.
-    if (scl) {
-        return i2css_blocking(slave);
-    }
-
-    // if it isn't, there must be some other communication going on, and it doesn't involve us
-    return I2CSS_BUS_BUSY;
+    // configure interrupt
+    GPIOA_ITModeCfg(1 << SDA_PIN, GPIO_ITMode_FallEdge);
 }
diff --git a/nametag8_CH592/user/comm/soft_i2c_slave.h b/nametag8_CH592/user/comm/soft_i2c_slave.h
index 26207bc..dea1800 100644
--- a/nametag8_CH592/user/comm/soft_i2c_slave.h
+++ b/nametag8_CH592/user/comm/soft_i2c_slave.h
@@ -17,9 +17,10 @@ typedef struct I2CSoftSlave {
     uint8_t addr;
     uint8_t addr_last_seen;
     uint16_t bit_time;
-    void   (*start_cb)();               // call on any new read/write operation
+    void    (*start_cb)();              // call on any new read/write operation
     uint8_t (*rd_cb)();                 // returns data
     int8_t  (*wr_cb)(uint8_t data);     // return 0 to ACK, all other NACK
+    void    (*err_cb)(uint8_t);         // called if there was an error during transfer
 } I2CSoftSlave;
 
 
@@ -29,6 +30,7 @@ enum I2CSoftSlave_Error {
     I2CSS_STOP,
     I2CSS_NACK,
     I2CSS_ADDR_NO_MATCH,
+    I2CSS_IN_TIMEOUT,
     // errors
     I2CSS_START_SCL_NOT_LOW         = -1,
     I2CSS_ADDR_READ_ERROR           = -2,   // could be timeout, start or stop condition detected
diff --git a/nametag8_CH592/user/comm/soft_i2c_slave_handler.c b/nametag8_CH592/user/comm/soft_i2c_slave_handler.c
deleted file mode 100644
index 9bcaa50..0000000
--- a/nametag8_CH592/user/comm/soft_i2c_slave_handler.c
+++ /dev/null
@@ -1,22 +0,0 @@
-/*
- * i2c_slave_handler.c
- *
- *  Created on: Oct 30, 2024
- *      Author: true
- */
-
-#include "soft_i2c_slave_handler.h"
-#include "soft_i2c_slave.h"
-
-#include <stdint.h>
-
-
-
-struct I2CSoftSlave addon_i2c;
-
-
-
-void i2css_addon_init()
-{
-
-}
diff --git a/nametag8_CH592/user/comm/soft_i2c_slave_handler.h b/nametag8_CH592/user/comm/soft_i2c_slave_handler.h
deleted file mode 100644
index 68389e8..0000000
--- a/nametag8_CH592/user/comm/soft_i2c_slave_handler.h
+++ /dev/null
@@ -1,17 +0,0 @@
-/*
- * soft_i2c_slave_handler.h
- *
- *  Created on: Oct 30, 2024
- *      Author: true
- */
-
-#ifndef USER_COMM_SOFT_I2C_SLAVE_HANDLER_H_
-#define USER_COMM_SOFT_I2C_SLAVE_HANDLER_H_
-
-
-
-extern struct I2CSoftSlave addon_i2c;
-
-
-
-#endif /* USER_COMM_SOFT_I2C_SLAVE_HANDLER_H_ */
diff --git a/nametag8_CH592/user/hw/gat/gat_i2c.c b/nametag8_CH592/user/hw/gat/gat_i2c.c
index c1aaaf0..6dad038 100644
--- a/nametag8_CH592/user/hw/gat/gat_i2c.c
+++ b/nametag8_CH592/user/hw/gat/gat_i2c.c
@@ -1,15 +1,38 @@
 /*
  * gat_i2c.c
  *
- *  Created on: Oct 11, 2024
- *      Author: true
- *
- * implements a shoddy i2c slave.
+ * implements a shoddy i2c slave for the addon header.
  * maximum speed 100KHz tested.
  * note: not yet tested.
+ *
+ * data is segmented by page. read always starts from byte 0 of selected page.
+ *
+ * write begins with 1 byte page index, followed by offset / index, followed by data.
+ *
+ *
+ * pages:
+ *
+ * - general: user input emulation and config functions.
+ *   data size is 2 bytes.
+ *   - 0: button input push mask. 0b0000_TL_TR_BR_BL.
+ *   - 1: button release mask.
+ *   - 2: nametag i2c clear timeout in frames. reverts to programmed name at 0. 0xff to disable.
+ *   not yet implemented.
+ *
+ * - nametag: live update the nae shown in nametag mode.
+ *   data size 16 bytes. byte 0 is length, bytes 1-15 are name data.
+ *   this does not change the nametag in settings / nvram, only the live update.
+ *   any update to this page will set general[1] to 0x20 if general[1] is not set to 0xff.
+ *   if length == 0, normal name will be shown. for empty screen, send a space character with length = 1.
+ *   example data:
+ *   0x84 (addr), 0x01 (nametag), 0x00 (start at first byte), 0x06 (name is 6 chars long), "Hello!"
+ *
+ * - raw: send raw data to the oled. send in 128 byte chunks.
+ *   not yet implemented.
  */
 
 #include <CH59x_common.h>
+#include "global.h"
 
 #include "gat_gpio.h"
 
@@ -19,104 +42,201 @@
 
 
 
-#define GAT_ADDR_BASE       0x30
-#define GAT_I2C_SPEED       100000
+#define GAT_ADDR_BASE           0x30
+#define GAT_I2C_SPEED           100000
 
-#define GAT_DATA_SIZE       256
+#define GAT_DATA_SIZE           128
+
+#define GAT_PAGE_GENERAL        0
+#define GAT_PAGE_NAMETAG_TEXT   1
+#define GAT_PAGE_RAW1           2
+#define GAT_PAGE_RAW2           3
+#define GAT_PAGE_RAW3           4
+#define GAT_PAGE_RAW4           5
+
+#define GAT_PAGESIZE_GENERAL    3
+#define GAT_PAGESIZE_NAMETAG    16
 
 
 
-struct I2CSoftSlave gat_slave;
+struct I2CSoftSlave addon_i2c;
 
 
 
 enum {
-    GAT_MODE_STARTING,
-    GAT_MODE_READ,
-    GAT_MODE_WRITE
+    I2C_STATE_STARTING,
+    I2C_STATE_READ,
+    I2C_STATE_OFFSET,
+    I2C_STATE_WRITE
 };
 
 
-uint8_t gat_state;
-uint16_t gat_data_idx;
-uint8_t gat_data[GAT_DATA_SIZE];
+static uint8_t i2c_state;
+
+static uint8_t gat_page = 0;
+static uint8_t gat_offset;
+
+static uint8_t page_general[GAT_PAGESIZE_GENERAL];
 
 
 
-uint8_t gat_i2c_read_cb()
+// page functions
+static uint8_t gat_read(uint8_t *page, uint8_t maxlen)
 {
-    uint8_t ret;
+    if (gat_offset > maxlen) return 0xff;
+    else return page[gat_offset++];
+}
 
-    switch (gat_state) {
-        case GAT_MODE_STARTING: {
-            gat_state = GAT_MODE_READ;
-            // no break
+uint8_t gat_page_general_get(uint8_t idx)
+{
+    if (idx > sizeof(page_general)) return 0;
+    else return page_general[idx];
+}
+
+uint8_t gat_page_general_set(uint8_t idx, uint8_t dat)
+{
+    if (idx >= sizeof(page_general)) return I2CSS_NACK;
+    page_general[idx] = dat;
+    return I2CSS_OK;
+}
+
+
+// i2c comms functions
+void addon_i2c_start_cb()
+{
+    i2c_state = I2C_STATE_STARTING;
+}
+
+// master reading from addon
+__HIGH_CODE
+uint8_t addon_i2c_read_cb()
+{
+    switch (i2c_state) {
+        case I2C_STATE_STARTING: {
+            i2c_state = I2C_STATE_READ;
+            gat_offset = 0;
         }
-        case GAT_MODE_READ: {
+        // no break
+
+        case I2C_STATE_READ: {
             // can't read past end of buffer; just send 0xff
-            if (gat_data_idx == GAT_DATA_SIZE) {
-                ret = 0xff;
-            } else {
-                ret = gat_data[gat_data_idx & 0xff];
-                if (gat_data_idx <= GAT_DATA_SIZE) gat_data_idx++;
+            switch (gat_page) {
+                case GAT_PAGE_GENERAL: {
+                    return gat_read(page_general, GAT_PAGESIZE_GENERAL);
+                }
+                case GAT_PAGE_NAMETAG_TEXT: {
+                    // to implement
+                    break;
+                }
+                case GAT_PAGE_RAW1:
+                case GAT_PAGE_RAW2:
+                case GAT_PAGE_RAW3:
+                case GAT_PAGE_RAW4: {
+                    // to implement
+                    break;
+                }
             }
-            return ret;
+
+            // data wasn't sent above, so send empty byte
+            return 0xff;
         }
+
         default: {
             return 0;
         }
     }
 }
 
-int8_t gat_i2c_write_cb(uint8_t dat)
+// master writing to addon
+__HIGH_CODE
+int8_t addon_i2c_write_cb(uint8_t dat)
 {
-    switch (gat_state) {
+    int8_t ret = I2CSS_OK;
 
-        case GAT_MODE_STARTING: {
+    switch (i2c_state) {
+        case I2C_STATE_STARTING: {
             // master wrote our address
-            gat_data_idx = dat;
-            gat_state = GAT_MODE_WRITE;
+            gat_page = dat;
+            i2c_state = I2C_STATE_OFFSET;
             break;
         }
-        case GAT_MODE_WRITE: {
-            if (gat_data_idx >= GAT_DATA_SIZE) {
-                return I2CSS_NACK;
-            } else {
-                gat_data[gat_data_idx++] = dat;
+
+        case I2C_STATE_OFFSET: {
+            gat_offset = dat;
+            i2c_state = I2C_STATE_WRITE;
+
+            if (gat_offset > GAT_DATA_SIZE) {
+                gat_offset = GAT_DATA_SIZE;
+                ret = I2CSS_NACK;
             }
-            return I2CSS_OK;
+
+            break;
         }
+
+        case I2C_STATE_WRITE: {
+            if (gat_offset >= GAT_DATA_SIZE) {
+                ret = I2CSS_NACK;
+                break;
+            }
+
+            switch (gat_page) {
+                case GAT_PAGE_GENERAL: {
+                    ret = gat_page_general_set(gat_offset, dat);
+                    break;
+                }
+                case GAT_PAGE_NAMETAG_TEXT: {
+                    // to implement
+                    ret = I2CSS_NACK;
+                    break;
+                }
+                case GAT_PAGE_RAW1:
+                case GAT_PAGE_RAW2:
+                case GAT_PAGE_RAW3:
+                case GAT_PAGE_RAW4: {
+                    // to implement
+                    ret = I2CSS_NACK;
+                    break;
+                }
+            }
+
+            gat_offset++;
+        }
+
         default: {
             return I2CSS_NACK;
         }
     }
+
+    return ret;
 }
 
-void gat_i2c_start_cb()
+void addon_i2c_err_cb(uint8_t error)
 {
-    gat_state = GAT_MODE_STARTING;
+
 }
 
 
-
-void gat_i2c_init()
+void addon_i2c_init()
 {
     // determine I2C address from GP pin identification
-    gat_slave.addr = gat_id + GAT_ADDR_BASE;
+    addon_i2c.addr = gat_id + GAT_ADDR_BASE;
 
     // roughly guess bit time length for expected speed
-    gat_slave.bit_time = GetSysClock() / GAT_I2C_SPEED / 4;
+    addon_i2c.bit_time = GetSysClock() / GAT_I2C_SPEED / 2;
 
     // set up callbacks
-    gat_slave.start_cb = gat_i2c_start_cb;
-    gat_slave.rd_cb = gat_i2c_read_cb;
-    gat_slave.wr_cb = gat_i2c_write_cb;
+    addon_i2c.start_cb = addon_i2c_start_cb;
+    addon_i2c.rd_cb = addon_i2c_read_cb;
+    addon_i2c.wr_cb = addon_i2c_write_cb;
+    addon_i2c.err_cb = addon_i2c_err_cb;
 
-    // enable interrupt on SDA pin to detect start condition
-    // this assumes GPIO has already been configured
+    // configure i2c pins and pin interrupt
+    i2css_init();
 }
 
-void gat_i2c_irq_cb()
+void addon_i2c_irq_cb()
 {
-    i2css_start(&gat_slave);
+    SetSysClock(SYSCLK_FREQ_USEI2C);
+    i2css_start(&addon_i2c);
+    SetSysClock(SYSCLK_FREQ_IDLE);
 }
diff --git a/nametag8_CH592/user/hw/gat/gat_i2c.h b/nametag8_CH592/user/hw/gat/gat_i2c.h
index 6f3b95a..bb89257 100644
--- a/nametag8_CH592/user/hw/gat/gat_i2c.h
+++ b/nametag8_CH592/user/hw/gat/gat_i2c.h
@@ -10,4 +10,13 @@
 
 
 
+void addon_i2c_init();
+
+void addon_i2c_irq_cb();
+
+uint8_t gat_page_general_get(uint8_t idx);
+void gat_page_general_set(uint8_t idx, uint8_t dat);
+
+
+
 #endif /* USER_GAT_GAT_I2C_H_ */
diff --git a/nametag8_CH592/user/main.c b/nametag8_CH592/user/main.c
index 161adbc..5edadcf 100644
--- a/nametag8_CH592/user/main.c
+++ b/nametag8_CH592/user/main.c
@@ -30,6 +30,7 @@
 #include "comm/i2c.h"
 
 #include "hw/gat/gat_gpio.h"
+#include "hw/gat/gat_i2c.h"
 
 #include "led/rgbled.h"
 
@@ -133,7 +134,7 @@ void rtcisr_init()
 
     rtc_reset_trig();
 
-    PFIC_SetPriority(RTC_IRQn, 0x10);       // rtc is second highest priority interrupt
+    PFIC_SetPriority(RTC_IRQn, 0x00);       // rtc is highest priority interrupt
     PFIC_EnableIRQ(RTC_IRQn);
 }
 
@@ -403,7 +404,7 @@ int main()
     rgbled_init();                      // initialize RGBLED controller
 
     gat_gpio_init();                    // configure GAT aux GPIOs, get gat ID
-    // todo: implement                  // configure GAT i2c slave
+    addon_i2c_init();                   // configure GAT i2c slave
 
     ssd1306fb_set_target(&oled);        // start up the OLED and menu system
     ssd1306_init(1);                    // we'll try to init later too, since sometimes OLED fails to init
diff --git a/nametag8_CH592/user/port_intr.c b/nametag8_CH592/user/port_intr.c
index 26ed606..f0b5c16 100644
--- a/nametag8_CH592/user/port_intr.c
+++ b/nametag8_CH592/user/port_intr.c
@@ -14,10 +14,8 @@
 #include "CH59x_common.h"
 #include "port_intr.h"
 
-#include "comm/soft_i2c_slave.h"
-#include "comm/soft_i2c_slave_handler.h"
-
 #include "hw/ch32sub.h"
+#include "hw/gat/gat_i2c.h"
 
 
 #include <stdint.h>
@@ -50,7 +48,7 @@ void port_intr_init()
     // clear state
     R16_PB_INT_IF = 0xff;
 
-    PFIC_SetPriority(GPIO_A_IRQn, 0x00);       // high priority
+    PFIC_SetPriority(GPIO_A_IRQn, 0x10);       // high priority
     PFIC_EnableIRQ(GPIO_A_IRQn);
 
     // then enable interrupt
@@ -72,9 +70,7 @@ void GPIOA_IRQHandler(void)
 
     // addon header i2c data pin
     if (flag & (1 << 13)) {
-        SetSysClock(SYSCLK_FREQ_USEI2C);
-        i2css_start(&addon_i2c);
-        SetSysClock(SYSCLK_FREQ_IDLE);
+        addon_i2c_irq_cb();
     }
 }
 
diff --git a/nametag8_CH592/user/user_config.c b/nametag8_CH592/user/user_config.c
index c6edc29..2b19333 100644
--- a/nametag8_CH592/user/user_config.c
+++ b/nametag8_CH592/user/user_config.c
@@ -62,6 +62,8 @@ void uconf_defaults()
 
     uconf.ledprog_rgb_idx   = 4;
 
+    uconf.addon_i2c_addr    = 0;
+
     for (i = 0; i < 8; i++) {
         uconf.ledprog_rgb[i] = 0;
     }
diff --git a/nametag8_CH592/user/user_config.h b/nametag8_CH592/user/user_config.h
index d6e8a33..ad588de 100644
--- a/nametag8_CH592/user/user_config.h
+++ b/nametag8_CH592/user/user_config.h
@@ -81,7 +81,7 @@ typedef struct UserConf {
     uint8_t  altcolor_sat;
     uint8_t  altcolor_val;                      // 50
     uint8_t  ledprog_rgb_idx;
-    uint8_t  padding0;                          // 52
+    uint8_t  addon_i2c_addr;                    // 52
     uint8_t  ledprog_rgb[16];                   // 68
     uint8_t  ledprog_rgb_data[16][8];           // 196
     uint8_t  padding1[48];                      // 244