diff --git a/main/CMakeLists.txt b/main/CMakeLists.txt
index 4d54565..8aea823 100644
--- a/main/CMakeLists.txt
+++ b/main/CMakeLists.txt
@@ -4,9 +4,11 @@ idf_component_register(SRCS "main.c"
 set(CARGO_BUILD_TYPE "release")
 set(CARGO_BUILD_ARG "--release")
 if(CONFIG_IDF_TARGET_ARCH_RISCV)
-    set(CARGO_TARGET "riscv32i-unknown-elf")
+    set(CARGO_TARGET "riscv32i-unknown-none-elf")
+    set(CARGO_FEATURES_ARG "")
 elseif(CONFIG_IDF_TARGET_ARCH_XTENSA)
-    set(CARGO_TARGET "xtensa-${CONFIG_IDF_TARGET}-none-elf")
+    set(CARGO_TARGET "xtensa-esp32-none-elf")
+    set(CARGO_FEATURES_ARG "--features=std")
 endif()
 
 set(RUST_PROJECT_DIR "${CMAKE_CURRENT_LIST_DIR}/../rustlib")
@@ -19,7 +21,7 @@ ExternalProject_Add(
     BUILD_COMMAND ${CMAKE_COMMAND} -E env
         CARGO_BUILD_TARGET=${CARGO_TARGET}
         CARGO_BUILD_TARGET_DIR=${RUST_BUILD_DIR}
-        cargo build ${CARGO_BUILD_ARG}
+        cargo build ${CARGO_BUILD_ARG} ${CARGO_FEATURES_ARG}
     DOWNLOAD_COMMAND ""
     CONFIGURE_COMMAND ""
     INSTALL_COMMAND ""
diff --git a/rustlib/Cargo.toml b/rustlib/Cargo.toml
index 822363e..ddf3f35 100644
--- a/rustlib/Cargo.toml
+++ b/rustlib/Cargo.toml
@@ -8,10 +8,12 @@ edition = "2018"
 crate-type = ["staticlib"]
 #crate-type = ["rlib", "staticlib"]
 
-
 [build-dependencies]
 bindgen = "0.58"
 
+[features]
+std = []
+
 [profile.dev]
 # Optimization level 1 is similar to "g" in gcc/clang, although for some reason
 # Cargo doesn't support that flag.
diff --git a/rustlib/bindings.rs b/rustlib/bindings.rs
deleted file mode 100644
index 995247a..0000000
--- a/rustlib/bindings.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-/* automatically generated by rust-bindgen 0.58.1 */
-
-pub const true_ : u32 = 1 ; pub const false_ : u32 = 0 ; pub const __bool_true_false_are_defined : u32 = 1 ; extern "C" { pub fn validate_param_in_c (param : :: std :: os :: raw :: c_int , value : :: std :: os :: raw :: c_int) -> bool ; }
\ No newline at end of file
diff --git a/rustlib/build.rs b/rustlib/build.rs
index 541fc0e..af64de6 100644
--- a/rustlib/build.rs
+++ b/rustlib/build.rs
@@ -1,40 +1,32 @@
 use std::env;
-use std::fs;
 use std::path::{Path, PathBuf};
 
 fn main() {
     let target = env::var("TARGET").unwrap();
 
-    // let cargo_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
-
+    let cargo_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
     let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
-    // fs::remove_dir_all(&out_dir).unwrap();
-    // fs::create_dir_all(&out_dir).unwrap();
 
-    // run_cbindgen(&cargo_dir, &out_dir);
+    run_cbindgen(&cargo_dir, &out_dir);
     run_bindgen(&target, &out_dir);
 }
 
-// fn run_cbindgen(_cargo_dir: &Path, _out_dir: &Path) {
+fn run_cbindgen(_cargo_dir: &Path, _out_dir: &Path) {
     // TODO: Run cbindgen
-// }
+}
 
 fn run_bindgen(target: &str, out_dir: &Path) {
-    // if target == "xtensa-esp32-none-elf" {
-    //     env::set_var("LLVM_CONFIG_PATH", "/usr/local/xtensa/llvm/bin/llvm-config");
-    // }
-
     let mut builder = bindgen::Builder::default();
     builder = builder.header("../main/CApi.h");
-    builder = builder.use_core();
-    builder = builder.ctypes_prefix("ffi");
-
-    println!("Target: {}", target);
     match target {
         "riscv32i-unknown-none-elf" => {
             builder = builder.clang_arg("--target=riscv32");
+            builder = builder.use_core();
+            builder = builder.ctypes_prefix("crate::ffi");
         }
         "xtensa-esp32-none-elf" => {
+            // Make sure that LLVM_CONFIG_PATH has been set to point to the
+            // Xtensa build of llvm-config.
             builder = builder.clang_arg("--target=xtensa-esp32-elf");
         }
         _ => {
diff --git a/rustlib/src/lib.rs b/rustlib/src/lib.rs
index 3528519..952604e 100644
--- a/rustlib/src/lib.rs
+++ b/rustlib/src/lib.rs
@@ -1,8 +1,12 @@
-// #![no_std]
+#![cfg_attr(not(feature = "std"), no_std)]
 
+#[cfg(not(feature = "std"))]
 use core::panic::PanicInfo;
 
-pub mod ffi {
+/// Create aliases for FFI types for esp32c3, which doesn't have std.
+#[cfg(not(feature = "std"))]
+mod ffi {
+    #![allow(dead_code)]
     #![allow(non_upper_case_globals)]
     #![allow(non_camel_case_types)]
     #![allow(non_snake_case)]
@@ -15,28 +19,20 @@ pub mod sys {
     #![allow(non_upper_case_globals)]
     #![allow(non_camel_case_types)]
     #![allow(non_snake_case)]
-
-    use crate::ffi;
     include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
 }
-use crate::sys::*;
-
-
-// #[panic_handler]
-// fn panic(_info: &PanicInfo) -> ! {
-//     loop {}
-// }
 
 #[no_mangle]
 pub extern "C" fn add_in_rust(x: i32, y: i32) -> i32 {
-
-    extern "C" {
-        fn validate_param_in_c(param: i32, value: i32) -> i32;
-    }
-
     unsafe {
-        validate_param_in_c(0, x);
-        validate_param_in_c(2, y);
+        sys::validate_param_in_c(0, x);
+        sys::validate_param_in_c(2, y);
     }
     x + y
 }
+
+#[cfg(not(feature = "std"))]
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    loop {}
+}