diff --git a/src/libboard_artiq/src/cxp_upconn.rs b/src/libboard_artiq/src/cxp_upconn.rs
index 06f8be3..baf96e6 100644
--- a/src/libboard_artiq/src/cxp_upconn.rs
+++ b/src/libboard_artiq/src/cxp_upconn.rs
@@ -28,10 +28,10 @@ pub fn tx_test(timer: &mut GlobalTimer) {
     // the 8bit shift is k symbol
     // const K28_1: u16 = 0x3C | (1 << 8);
     // const K28_5: u16 = 0xBC | (1 << 8);
-    const D31_1: u16 = 0x3F;
     const D01_1: u16 = 0x21;
+    const D31_1: u16 = 0x3F;
 
-    const LEN: usize = 100;
+    const LEN: usize = 200;
     let mut arr: [u16; LEN] = [0; LEN];
 
     unsafe {
@@ -40,40 +40,47 @@ pub fn tx_test(timer: &mut GlobalTimer) {
         csr::cxp::upconn_clk_reset_write(0);
         loop {
             // TODO: verify the char & word boundary thingy
-            for _ in 0..8 {
-                csr::cxp::upconn_symbol1_write(D01_1);
-            }
-
-            for _ in 0..4 {
+            for _ in 0..12 {
                 csr::cxp::upconn_symbol2_write(D31_1);
             }
 
-            timer.delay_us(1);
             csr::cxp::upconn_tx_enable_write(1);
+            timer.delay_us(1);
+
+            for _ in 0..3 {
+                csr::cxp::upconn_symbol0_write(D01_1);
+            }
 
             for i in 0..LEN {
                 arr[i] = get_encoded();
             }
+            let mut last_encoded: u16 = 0;
             for i in 0..LEN {
-                match arr[i] {
-                    0b1010111001 | 0b0101001001 => {
-                        println!("encoded = {:#012b} D31.1", arr[i])
-                    }
-                    0b0111011001 | 0b1000101001 => {
-                        println!("encoded = {:#012b} D01.1", arr[i])
-                    }
-                    0b0011111010 | 0b1100000101 => {
-                        println!("encoded = {:#012b} K28.5 start idling....", arr[i])
-                    }
-                    0b0011111001 | 0b1100000110 => {
-                        println!("encoded = {:#012b} K28.1 idling...", arr[i])
-                    }
-                    0b0011101010 => {
-                        println!("encoded = {:#012b} D28.5 END idle", arr[i])
-                    }
-                    _ => {
-                        println!("encoded = {:#012b}", arr[i])
+                if last_encoded != arr[i] {
+                    match arr[i] {
+                        0b1010111001 | 0b0101001001 => {
+                            println!("D31.1")
+                        }
+                        0b0111011001 | 0b1000101001 => {
+                            println!("D01.1")
+                        }
+                        0b1101010010 | 0b0010101101 => {
+                            println!("D04.4")
+                        }
+                        0b0011111010 | 0b1100000101 => {
+                            println!("K28.5 start idling....")
+                        }
+                        0b0011111001 | 0b1100000110 => {
+                            println!("K28.1 idling...")
+                        }
+                        0b0011101010 => {
+                            println!("D28.5 END idle")
+                        }
+                        _ => {
+                            println!("encoded = {:#012b}", arr[i])
+                        }
                     }
+                    last_encoded = arr[i]
                 }
             }
             println!("-------------------------------------");