diff --git a/src/libboard_artiq/src/cxp_downconn.rs b/src/libboard_artiq/src/cxp_downconn.rs
index 778b2f8..e8211b7 100644
--- a/src/libboard_artiq/src/cxp_downconn.rs
+++ b/src/libboard_artiq/src/cxp_downconn.rs
@@ -3,7 +3,7 @@ use libboard_zynq::{println, timer::GlobalTimer};
 use log::info;
 
 // use log::info;
-use crate::pl::csr;
+use crate::{cxp_proto, pl::csr};
 
 #[derive(Clone, Copy, Debug)]
 #[allow(non_camel_case_types)]
@@ -37,71 +37,36 @@ pub fn loopback_testing(timer: &mut GlobalTimer, speed: CXP_SPEED) {
         while csr::cxp::downconn_phy_rx_ready_read() != 1 {}
         info!("rx ready!");
 
-        loop {
-            // for _ in 0..20 {
-            // NOTE: raw bits
-            // let data0 = csr::cxp::downconn_phy_rxdata_0_read();
-            // let data1 = csr::cxp::downconn_phy_rxdata_1_read();
-            // let data2 = csr::cxp::downconn_phy_rxdata_2_read();
-            // let data3 = csr::cxp::downconn_phy_rxdata_3_read();
-            // let rxready = csr::cxp::downconn_phy_rx_ready_read();
-            // timer.delay_us(100);
-            // if data0 == 0b0101111100 || data0 == 0b1010000011 {
-            //     println!(
-            //         "data[0] = {:#012b} comma = {} | rx ready = {}",
-            //         data0,
-            //         data0 == 0b0101111100 || data0 == 0b1010000011,
-            //         rxready,
-            //     );
-            //     timer.delay_us(1_000_000);
-            // } else if data0 == 0b1001111100 || data0 == 0b0110000011 {
-            //     println!(
-            //         "data[0] = {:#012b} K28.1 | rx ready = {}",
-            //         data0,
-            //         rxready,
-            //     );
-            //     timer.delay_us(1_000_000);
-            // } else {
-            //     println!(
-            //         "data[0] = {:#012b} | rx ready = {}",
-            //         data0,
-            //         rxready,
-            //     );
-            //     timer.delay_us(1_000_000);
-            // }
+        cxp_proto::downconn_debug_send(&cxp_proto::Packet::CtrlRead {
+            addr: 0x00,
+            length: 0x04,
+        });
 
-            timer.delay_us(1_000_000);
-            // NOTE: raw bits
-            // let data0 = csr::cxp::downconn_phy_rxdata_0_read();
-            // let data1 = csr::cxp::downconn_phy_rxdata_1_read();
-            // let data2 = csr::cxp::downconn_phy_rxdata_2_read();
-            // let data3 = csr::cxp::downconn_phy_rxdata_3_read();
-            // println!(
-            //     "0b{:010b} {:010b} {:010b} {:010b}",
-            //     data0, data1, data2, data3
-            // );
-
-            // NOTE:decode data
-            // let data0_k = csr::cxp::downconn_phy_decoded_k_0_read();
-            // let data1_k = csr::cxp::downconn_phy_decoded_k_1_read();
-            // let data2_k = csr::cxp::downconn_phy_decoded_k_2_read();
-            // let data3_k = csr::cxp::downconn_phy_decoded_k_3_read();
-            let data0_decoded = csr::cxp::downconn_phy_decoded_data_0_read();
-            let data1_decoded = csr::cxp::downconn_phy_decoded_data_1_read();
-            let data2_decoded = csr::cxp::downconn_phy_decoded_data_2_read();
-            let data3_decoded = csr::cxp::downconn_phy_decoded_data_3_read();
-            println!(
-                "{:#04x} {:#04x} {:#04x} {:#04x}",
-                data0_decoded, data1_decoded, data2_decoded, data3_decoded,
-            );
-            // println!(
-            //     "decoded_data[0] = {:#04x} decoded_k[0] = {:#b} decoded_data[1] = {:#04x} decoded_k[1] = {:#b}",
-            //     data0_decoded,
-            //     data0_k,
-            //     data1_decoded,
-            //     data1_k,
-            // );
+        timer.delay_us(200); // wait packet has arrive at async fifo in
+        unsafe {
+            csr::cxp::downconn_phy_tx_stb_write(1);
+            timer.delay_us(200);
+            csr::cxp::downconn_phy_tx_stb_write(0);
         }
+
+        // TODO: investigate how to make my packet appear
+        // TODO: discard idle word
+
+        const LEN: usize = 20;
+        let mut pak_arr: [u32; LEN] = [0; LEN];
+        let mut i: usize = 0;
+        unsafe {
+            while csr::cxp::downconn_debug_out_dout_valid_read() == 1 {
+                pak_arr[i] = csr::cxp::downconn_debug_out_dout_pak_read();
+                // println!("received {:#04X}", pak_arr[i]);
+                csr::cxp::downconn_debug_out_inc_write(1);
+                i += 1;
+                if i == LEN {
+                    break;
+                }
+            }
+        }
+        cxp_proto::print_packetu32(&pak_arr)
     }
 }