diff --git a/Cargo.toml b/Cargo.toml
index 1c3de80..8602951 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,8 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
-postcard-rpc = { version = "0.11.12" }
+postcard-rpc = { version = "0.11.15" }
+heapless = { version = "0.9.0", features = ["serde"] }
 
 [dependencies.serde]
 version = "1.0.219"
@@ -12,8 +13,8 @@ features = ["derive"]
 default-features = false
 
 [dependencies.postcard-schema]
-version = "0.2.4"
-features = ["derive"]
+version = "0.2.5"
+features = ["derive", "heapless-v0_9"]
 
 [features]
 use-std = []
diff --git a/src/lib.rs b/src/lib.rs
index 6875422..dba4d4a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,19 +3,29 @@
 use postcard_rpc::{endpoints, topics, TopicDirection};
 use postcard_schema::Schema;
 use serde::{Deserialize, Serialize};
+use heapless::Vec;
 
 // ---
 
+#[derive(Serialize, Deserialize, Schema, Debug, PartialEq)]
+pub enum InitImpedanceError {
+    DSPNotSet,
+}
+
+pub type InitImpedanceResult = Result<f32, InitImpedanceError>;
+
 endpoints! {
     list = ENDPOINT_LIST;
     omit_std = true;
-    | EndpointTy                | RequestTy      | ResponseTy            | Path              |
-    | ----------                | ---------      | ----------            | ----              |
-    | PingEndpoint              | u32            | u32                   | "ping"            |
-    | GetUniqueIdEndpoint       | ()             | [u8; 12]              | "get_id"          |
-    | SetGreenLedEndpoint       | f32            | ()                    | "led/green"      |
-    | StartImpedanceEndpoint    | StartImpedance | ()                    | "imp/start"     |
-    | StopImpedanceEndpoint     | ()             | bool                  | "imp/stop"      |
+    | EndpointTy                    | RequestTy            | ResponseTy      | Path                |
+    | ----------                    | ---------            | ----------      | ----                |
+    | PingEndpoint                  | u32                  | u32             | "ping"              |
+    | GetUniqueIdEndpoint           | ()                   | [u8; 12]        | "get_id"            |
+    | SetGreenLedEndpoint           | f32                  | ()              | "led/green"         |
+    | StartSingleImpedanceEndpoint  | StartSingleImpedance | InitImpedanceResult | "imp/start_single"  |
+    | StopSingleImpedanceEndpoint   | ()                   | bool            | "imp/stop_single"   |
+    | StartMultiImpedanceEndpoint   | StartMultiImpedance  | ()              | "imp/start_multi"   |
+    | StopMultiImpedanceEndpoint    | ()                   | bool            | "imp/stop_multi"    |
 }
 
 topics! {
@@ -28,17 +38,24 @@ topics! {
 topics! {
     list = TOPICS_OUT_LIST;
     direction = TopicDirection::ToClient;
-    | TopicTy                   | MessageTy       | Path              | Cfg                           |
-    | -------                   | ---------       | ----              | ---                           |
-    | ImpedanceOutputTopic      | ImpedanceOutput | "imp/data"        |                               |
+    | TopicTy                         | MessageTy                   | Path              | Cfg                   |
+    | -------                         | ---------                   | ----              | ---                   |
+    | SingleImpedanceOutputTopic      | SingleImpedanceOutput       | "imp/single"      |                       |
+    | MultiImpedanceOutputTopic28     | MultiImpedanceOutput28      | "imp/multi"       |                       |
 }
 
 #[derive(Serialize, Deserialize, Schema, Debug, PartialEq)]
-pub struct ImpedanceOutput {
+pub struct SingleImpedanceOutput {
     pub magnitude: f32,
     pub phase: f32,
 }
 
+#[derive(Serialize, Deserialize, Schema, Debug, PartialEq)]
+pub struct MultiImpedanceOutput28 {
+    pub magnitudes: Vec<f32, 28>,
+    pub phases: Vec<f32, 28>,
+}
+
 #[derive(Clone, Copy, Serialize, Deserialize, Schema, Debug, PartialEq)]
 pub enum IcdDftNum {
     Num4,
@@ -57,8 +74,34 @@ pub enum IcdDftNum {
 }
 
 #[derive(Serialize, Deserialize, Schema, Debug, PartialEq)]
-pub struct StartImpedance {
+pub struct StartSingleImpedance {
     pub update_frequency: u32,
     pub sinus_frequency: u32,
     pub dft_number: IcdDftNum,
 }
+
+#[derive(Clone, Copy, Serialize, Deserialize, Schema, Debug, PartialEq)]
+pub enum NumberOfPoints {
+    TwentyEight,
+}
+
+impl NumberOfPoints {
+    pub fn values(&self) -> &'static [f32] {
+        match self {
+            NumberOfPoints::TwentyEight => {
+                &[1.0, 1.6, 2.5, 4.0, 6.3, 
+                10.0, 16.0, 25.0, 40.0, 63.0, 
+                100.0, 160.0, 250.0, 400.0, 630.0, 
+                1000.0, 1600.0, 2500.0, 4000.0, 6300.0, 
+                10000.0, 16000.0, 25000.0, 40000.0, 63000.0, 
+                100000.0, 160000.0, 200000.0]
+            }
+        }
+    }
+}
+
+#[derive(Serialize, Deserialize, Schema, Debug, PartialEq)]
+pub struct StartMultiImpedance {
+    pub dft_number: IcdDftNum,
+    pub number_of_points: NumberOfPoints,
+}