diff --git a/advanced/firmware/Cargo.toml b/advanced/firmware/Cargo.toml
index 6e72cfd..cc7c147 100644
--- a/advanced/firmware/Cargo.toml
+++ b/advanced/firmware/Cargo.toml
@@ -16,7 +16,7 @@ cortex-m = "0.7.6"
 cortex-m-rt = "0.7.2"
 cortex-m-rtic = "1.1.3"
 defmt = "0.3.2"
-defmt-rtt = "0.3.2"
+defmt-rtt = "0.4.1"
 dk = { path = "../../boards/dk", features = ["advanced"] }
 panic-probe = { version = "0.3.0", features = ["print-defmt"] }
 usb = { path = "../common/usb" }
@@ -33,7 +33,7 @@ debug = 2
 debug-assertions = true # !
 incremental = false
 lto = "fat"
-opt-level = 'z' # !
+opt-level = 'z'         # !
 overflow-checks = false
 
 [profile.release]
@@ -44,4 +44,3 @@ incremental = false
 lto = "fat"
 opt-level = 3
 overflow-checks = false
-
diff --git a/beginner/apps/Cargo.toml b/beginner/apps/Cargo.toml
index 61ee794..682712e 100644
--- a/beginner/apps/Cargo.toml
+++ b/beginner/apps/Cargo.toml
@@ -6,13 +6,13 @@ name = "apps"
 version = "0.0.0"
 
 [dependencies]
-cortex-m = {version = "0.7.6", features = ["critical-section-single-core"]}
+cortex-m = { version = "0.7.6", features = ["critical-section-single-core"] }
 cortex-m-rt = "0.7.2"
 dk = { path = "../../boards/dk", features = ["beginner"] }
 heapless = "0.7.16"
 panic-probe = { version = "0.3.0", features = ["print-defmt"] }
 defmt = "0.3.2"
-defmt-rtt = "0.3.2"
+defmt-rtt = "0.4.1"
 
 # optimize code in both profiles
 [profile.dev]
@@ -21,7 +21,7 @@ debug = 2
 debug-assertions = true # !
 incremental = false
 lto = "fat"
-opt-level = 'z' # !
+opt-level = 'z'         # !
 overflow-checks = false
 
 [profile.release]
@@ -35,9 +35,7 @@ overflow-checks = false
 
 [features]
 
-default = [
-  "other-feature"
-]
+default = ["other-feature"]
 other-feature = []
 # do NOT modify these features
 defmt-default = []
@@ -45,4 +43,4 @@ defmt-trace = []
 defmt-debug = []
 defmt-info = []
 defmt-warn = []
-defmt-error = []
\ No newline at end of file
+defmt-error = []
diff --git a/boards/dk/Cargo.toml b/boards/dk/Cargo.toml
index aebbd62..024e1c8 100644
--- a/boards/dk/Cargo.toml
+++ b/boards/dk/Cargo.toml
@@ -6,21 +6,19 @@ name = "dk"
 version = "0.0.0"
 
 [dependencies]
-cortex-m = {version = "0.7.6", features = ["critical-section-single-core"]}
+cortex-m = { version = "0.7.6", features = ["critical-section-single-core"] }
 cortex-m-rt = "0.7.2"
 embedded-hal = "0.2.7"
 hal = { package = "nrf52840-hal", version = "0.14.0" }
 panic-probe = { version = "0.3.0", features = ["print-defmt"] }
 defmt = "0.3.2"
-defmt-rtt = "0.3.2"
+defmt-rtt = "0.4.1"
 
 [features]
 advanced = []
 beginner = []
 
-default = [
-  "other-feature"
-]
+default = ["other-feature"]
 other-feature = []
 
 # do NOT modify these features
diff --git a/boards/dk/src/lib.rs b/boards/dk/src/lib.rs
index 477fd6f..e3f0d6d 100644
--- a/boards/dk/src/lib.rs
+++ b/boards/dk/src/lib.rs
@@ -3,6 +3,7 @@
 #![deny(missing_docs)]
 #![deny(warnings)]
 #![no_std]
+#![allow(static_mut_refs)]
 
 use core::{
     ops,