diff --git a/nametag8_V003/user/ch32v00x_it.c b/nametag8_V003/user/ch32v00x_it.c
index 8b29546..d3b2240 100644
--- a/nametag8_V003/user/ch32v00x_it.c
+++ b/nametag8_V003/user/ch32v00x_it.c
@@ -31,6 +31,7 @@ void HardFault_Handler(void)
     while (1);
 }
 
+__attribute__((interrupt("WCH-Interrupt-fast")))
 void SysTick_Handler(void)
 {
     // ---- PROCESS UI AND COMMS
diff --git a/nametag8_V003/user/i2c_slave.c b/nametag8_V003/user/i2c_slave.c
index 8ff8b59..8a05747 100644
--- a/nametag8_V003/user/i2c_slave.c
+++ b/nametag8_V003/user/i2c_slave.c
@@ -9,7 +9,8 @@
  * some notes:
  * - writing does not loop; if writing to the end then new writes will cause an error interrupt.
  * - added write protection for first 16 bytes.
- * - many registers will only commit to action upon valid I2C stop received.
+ * - the code don't send NACKs on invalid writes.
+ * - write registers will only commit to action upon valid I2C stop received.
  *
  *
  * register map:
@@ -129,8 +130,8 @@ void i2cs_write_cb(uint16_t initial_reg, uint16_t last_reg)
 // error - see i2c_slave.h for error types
 void i2cs_werr_cb(uint16_t reg, uint8_t data, uint8_t error)
 {
-    i2cs_reg[0x0d]++;
-    if (!i2cs_reg[0x0d]) i2cs_reg[0x0c]++;
+    i2cs_reg[REG_WERR_LO]++;
+    if (!i2cs_reg[REG_WERR_LO]) i2cs_reg[REG_WERR_HI]++;
 }
 
 // called upon every register read
@@ -208,7 +209,7 @@ void I2C1_EV_IRQHandler(void)
         i2cs_state.position = i2cs_state.offset; // Reset position
     }
 
-    if (STAR1 & I2C_STAR1_RXNE) { // Write event
+    if (STAR1 & I2C_STAR1_RXNE) { // Write from master event
         if (i2cs_state.first_write == 2) { // low address byte written; set the offset
             i2cs_state.offset = i2cs_state.offset | I2C1->DATAR;
             i2cs_state.position = i2cs_state.offset;
@@ -240,7 +241,7 @@ void I2C1_EV_IRQHandler(void)
         }
     }
 
-    if (STAR1 & I2C_STAR1_TXE) { // Read event
+    if (STAR1 & I2C_STAR1_TXE) { // Read to master event
         i2cs_state.writing = 0;
         if (i2cs_state.position < i2cs_state.reg_len) {
             I2C1->DATAR = i2cs_state.reg_file[i2cs_state.position];
@@ -262,6 +263,7 @@ void I2C1_EV_IRQHandler(void)
     }
 }
 
+__attribute__((interrupt("WCH-Interrupt-fast")))
 void I2C1_ER_IRQHandler(void)
 {
     uint16_t STAR1 = I2C1->STAR1;
diff --git a/nametag8_V003/user/main.c b/nametag8_V003/user/main.c
index 84f62ef..3f3a7b8 100644
--- a/nametag8_V003/user/main.c
+++ b/nametag8_V003/user/main.c
@@ -140,6 +140,7 @@ int main(void)
     exti_nvic_init();
 
     // configure systick
+    systick_init();
 
     while (1) {
         __WFI();