diff --git a/embassy-stm32/build.rs b/embassy-stm32/build.rs
index a6434a7e..ed2b4c50 100644
--- a/embassy-stm32/build.rs
+++ b/embassy-stm32/build.rs
@@ -1,6 +1,6 @@
 use std::env;
+use std::fs;
 use std::path::PathBuf;
-use std::process::Command;
 
 fn main() {
     let chip_name = env::vars_os()
@@ -11,17 +11,72 @@ fn main() {
         .unwrap()
         .to_ascii_lowercase();
 
+    struct Peripheral {
+        kind: String,
+        name: String,
+    }
+
+    let mut peripherals: Vec<Peripheral> = Vec::new();
+    stm32_metapac::peripherals!(
+        ($kind:ident, $name:ident) => {
+            peripherals.push(Peripheral{
+                kind: stringify!($kind).to_string(),
+                name: stringify!($name).to_string(),
+            });
+        };
+    );
+
+    let mut singletons: Vec<String> = Vec::new();
+    for p in peripherals {
+        match p.kind.as_str() {
+            // Generate singletons per pin, not per port
+            "gpio" => {
+                println!("{}", p.name);
+                let port_letter = p.name.strip_prefix("GPIO").unwrap();
+                for pin_num in 0..16 {
+                    singletons.push(format!("P{}{}", port_letter, pin_num));
+                }
+            }
+
+            // No singleton for these, the HAL handles them specially.
+            "exti" => {}
+
+            // We *shouldn't* have singletons for these, but the HAL currently requires
+            // singletons, for using with RccPeripheral to enable/disable clocks to them.
+            //"rcc" => {}
+            //"dbgmcu" => {}
+            //"syscfg" => {}
+            //"dma" => {}
+            //"bdma" => {}
+            //"dmamux" => {}
+
+            // For other peripherals, one singleton per peri
+            _ => singletons.push(p.name.clone()),
+        }
+    }
+
+    // One singleton per EXTI line
+    for pin_num in 0..16 {
+        singletons.push(format!("EXTI{}", pin_num));
+    }
+
+    // One singleton per DMA channel
+    stm32_metapac::dma_channels! {
+        ($channel_peri:ident, $dma_peri:ident, $version:ident, $channel_num:expr, $ignore:tt) => {
+            singletons.push(stringify!($channel_peri).to_string());
+        };
+    }
+
     let out_dir = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
     let out_file = out_dir.join("generated.rs").to_string_lossy().to_string();
-
-    let exit_code = Command::new("python3")
-        .args(&["gen.py", &chip_name, &out_file])
-        .status()
-        .expect("failed to execute gen.py");
-
-    if !exit_code.success() {
-        panic!("gen.py exited with {:?}", exit_code)
-    }
+    fs::write(
+        out_file,
+        format!(
+            "embassy_hal_common::peripherals!({});",
+            singletons.join(",")
+        ),
+    )
+    .unwrap();
 
     stm32_metapac::peripheral_versions!(
         ($peri:ident, $version:ident) => {
diff --git a/embassy-stm32/gen.py b/embassy-stm32/gen.py
deleted file mode 100644
index e589f2f0..00000000
--- a/embassy-stm32/gen.py
+++ /dev/null
@@ -1,88 +0,0 @@
-import sys
-import yaml
-import re
-import os
-import re
-
-try:
-    from yaml import CSafeLoader as SafeLoader
-except ImportError:
-    from yaml import SafeLoader
-
-
-abspath = os.path.abspath(__file__)
-dname = os.path.dirname(abspath)
-os.chdir(dname)
-
-data_path = '../stm32-data/data'
-
-try:
-    _, chip_name, output_file = sys.argv
-except:
-    raise Exception("Usage: gen.py STM32F429ZI_CM0 path/to/generated.rs")
-
-c = chip_name.split('_', 1)
-
-chip_name = c[0].upper()
-core_name = None
-
-if len(c) > 1:
-    core_name = c[1].lower()
-
-# ======= load chip
-with open(f'{data_path}/chips/{chip_name}.yaml', 'r') as f:
-    chip = yaml.load(f, Loader=SafeLoader)
-
-# ======= Generate!
-with open(output_file, 'w') as f:
-    singletons = []  # USART1, PA5, EXTI8
-    exti_interrupts = []  # EXTI IRQs, EXTI0, EXTI4_15 etc.
-    pins = set()  # set of all present pins. PA4, PA5...
-
-    # ========= peripherals
-
-    singletons.extend((f'EXTI{x}' for x in range(16)))
-    num_dmas = 0
-
-    core = chip['cores'][0]
-    if core_name != None:
-        for c in chip['cores']:
-            if core_name == c['name']:
-                core = c
-
-    for (name, peri) in core['peripherals'].items():
-        if 'block' not in peri:
-            continue
-
-        block = peri['block']
-        block_mod, block_name_unparsed = block.rsplit('/')
-        block_mod, block_version = block_mod.rsplit('_')
-        block_name = ''
-        for b in block_name_unparsed.split('_'):
-            block_name += b.capitalize()
-
-        custom_singletons = False
-
-        if block_mod == 'gpio':
-            custom_singletons = True
-            port = name[4:]
-            port_num = ord(port) - ord('A')
-
-            for pin_num in range(16):
-                pin = f'P{port}{pin_num}'
-                pins.add(pin)
-                singletons.append(pin)
-
-        # if block_mod == 'dma':
-        #     custom_singletons = True
-        #     for ch_num in range(8):
-        #         channel = f'{name}_CH{ch_num}'
-        #         singletons.append(channel)
-
-        if not custom_singletons:
-            singletons.append(name)
-
-    for (channel_id, defn) in core['dma_channels'].items():
-        singletons.append( channel_id )
-
-    f.write(f"embassy_hal_common::peripherals!({','.join(singletons)});")