diff --git a/src/libboard_artiq/src/cxp_ctrl.rs b/src/libboard_artiq/src/cxp_ctrl.rs
index f634b7f..0265132 100644
--- a/src/libboard_artiq/src/cxp_ctrl.rs
+++ b/src/libboard_artiq/src/cxp_ctrl.rs
@@ -4,11 +4,10 @@ use byteorder::{ByteOrder, NetworkEndian};
 use io::Cursor;
 use libboard_zynq::{println, time::Milliseconds, timer::GlobalTimer};
 
-use crate::{cxp_proto::{print_packet, Error, RXPacket, TXPacket, DATA_MAXSIZE},
+use crate::{cxp_proto::{print_packet, Error, RXPacket, TXPacket, CTRL_PACKET_MAXSIZE, DATA_MAXSIZE},
             mem::mem::CXP_MEM,
             pl::csr::CXP};
 
-const BUF_LEN: usize = 0x800;
 const TRANSMISSION_TIMEOUT: u64 = 200;
 
 fn packet_pending(channel: u8) -> bool {
@@ -21,9 +20,10 @@ fn receive(channel: u8) -> Result<Option<RXPacket>, Error> {
         unsafe {
             let read_buffer_ptr = (CXP[channel].rx_read_ptr_read)() as usize;
             println!("buffer ptr = {}", read_buffer_ptr);
-            let ptr = (CXP_MEM[channel].base + CXP_MEM[channel].size / 2 + read_buffer_ptr * BUF_LEN) as *mut u32;
+            let ptr =
+                (CXP_MEM[channel].base + CXP_MEM[channel].size / 2 + read_buffer_ptr * CTRL_PACKET_MAXSIZE) as *mut u32;
 
-            let mut reader = Cursor::new(slice::from_raw_parts_mut(ptr as *mut u8, BUF_LEN));
+            let mut reader = Cursor::new(slice::from_raw_parts_mut(ptr as *mut u8, CTRL_PACKET_MAXSIZE));
             let packet_type = (CXP[channel].rx_packet_type_read)();
             println!("packet_type = {}", packet_type);
             // DEBUG:
@@ -60,14 +60,14 @@ fn send_data_packet(channel: u8, packet: &TXPacket) -> Result<(), Error> {
     unsafe {
         while (CXP[channel].tx_writer_busy_read)() == 1 {}
         let ptr = CXP_MEM[channel].base as *mut u32;
-        let mut writer = Cursor::new(slice::from_raw_parts_mut(ptr as *mut u8, BUF_LEN));
+        let mut writer = Cursor::new(slice::from_raw_parts_mut(ptr as *mut u8, CTRL_PACKET_MAXSIZE));
 
         packet.write_to(&mut writer)?;
         // DEBUG:
         // println!("TX MEM after writing");
         // print_packet(&writer.get_ref()[0..40]);
 
-        (CXP[channel].tx_writer_word_len_write)(writer.position() as u16 / 4);
+        (CXP[channel].tx_writer_word_len_write)((writer.position() / 4) as u8);
         (CXP[channel].tx_writer_stb_write)(1);
     }
 
@@ -92,7 +92,7 @@ pub fn send_test_packet(channel: u8) -> Result<(), Error> {
 pub fn rx_debug_mem_print(channel: u8) {
     unsafe {
         let ptr = CXP_MEM[channel as usize].base as *mut u32;
-        let arr = slice::from_raw_parts_mut(ptr as *mut u8, BUF_LEN * 4);
+        let arr = slice::from_raw_parts_mut(ptr as *mut u8, CTRL_PACKET_MAXSIZE * 4);
         print_packet(arr);
     }
 }