fw: refactor timer stuff into its own module

firmware/src/main.rs

@@ -7,7 +7,6 @@ extern crate panic_halt;
 
 use core::fmt::Write;
 use core::{
-    arch::asm,
     ptr::{read_volatile, write_volatile},
 };
 
@@ -33,11 +32,12 @@ mod mcp4726;
 mod proto;
 mod uart;
 mod sampler;
+mod timer;
+
+use timer::millis;
 
 const MAC: [u8; 6] = [0xA0, 0xBB, 0xCC, 0xDD, 0xEE, 0xF0];
 
-static mut SECONDS: u32 = 0;
-
 // use `main` as the entry point of this application
 // `main` is not allowed to return
 #[entry]
@@ -111,13 +111,7 @@ fn main() -> ! {
     //defmt::info!("Done setup");
 
     // Set up timer for polling events
-    unsafe {
+    timer::init();
-        // Timer stuff
-        write_reg(0xf000_3808, 0u32); // Disable timer
-        write_reg(0xf000_3800, 0u32); // Set LOAD value
-        write_reg(0xf000_3804, 60_000_000u32); // Set RELOAD value
-        write_reg(0xf000_3808, 1u32); // Enable timer
-    }
 
     let mut cmd = command_interface::CommandInterface::new();
 
@@ -156,33 +150,11 @@ fn main() -> ! {
 
         // TODO I think the timer might actually stop until the event is cleared? this may pose
         // problems, might explain why moving this above the smoltcp stuff "broke" things
-        handle_timer_event();
+        timer::poll();
 
     }
 }
 
-fn handle_timer_event() {
-    unsafe {
-        if read_reg::<u32>(0xf000_3818) == 0 {
-            // No event yet, continue
-            return;
-        }
-
-        // Clear TIMER0 event status, and update time
-        write_reg(0xf000_3818, 1u32);
-        SECONDS += 1;
-    }
-}
-
-fn busy_wait(ms: u32) {
-    let start = millis();
-    while millis() - start < ms {
-        unsafe {
-            asm!("nop");
-        }
-    }
-}
-
 fn write_led(val: u32) {
     unsafe {
         write_reg(0xf000_2000, val);
@@ -196,16 +168,3 @@ unsafe fn write_reg<T>(addr: u32, value: T) {
 unsafe fn read_reg<T>(addr: u32) -> T {
     return read_volatile(addr as *mut T);
 }
-
-fn millis() -> u32 {
-    riscv::interrupt::free(|| {
-        unsafe {
-            // Latch timer value
-            write_reg(0xf000_380c, 1u32);
-            // Read timer value
-            let val: u32 = read_reg(0xf000_3810);
-            let val = 60_000_000 - val;
-            (SECONDS * 1000) + val / 60_000
-        }
-    })
-}

firmware/src/timer.rs

@@ -0,0 +1,79 @@
+//! Simple module to use LiteX TIMER0 for simple timekeeping
+
+use crate::{read_reg, write_reg};
+use core::arch::asm;
+
+/// Initializes the timer to use for polling events as a wall clock.
+///
+/// Timer is running at system frequency (60MHz)
+pub fn init() {
+    unsafe {
+        write_reg(0xf000_3808, 0u32); // Disable timer
+        write_reg(0xf000_3800, 0u32); // Set LOAD value
+        write_reg(0xf000_3804, 60_000_000u32); // Set RELOAD value
+        write_reg(0xf000_3808, 1u32); // Enable timer
+    }
+}
+
+// Storage for overflow time
+static mut SECONDS: u32 = 0;
+
+/// Processes potential timer events. Must be polled regularly
+pub fn poll() {
+    unsafe {
+        if read_reg::<u32>(0xf000_3818) == 0 {
+            // No event yet, continue
+            return;
+        }
+
+        // Clear TIMER0 event status, and update time
+        write_reg(0xf000_3818, 1u32);
+        SECONDS += 1;
+    }
+}
+
+/// Gets system time in milliseconds
+pub fn millis() -> u32 {
+    riscv::interrupt::free(|| {
+        unsafe {
+            // Latch timer value
+            write_reg(0xf000_380c, 1u32);
+            // Read timer value
+            let val: u32 = read_reg(0xf000_3810);
+            let val = 60_000_000 - val;
+            (SECONDS * 1000) + val / 60_000
+        }
+    })
+}
+
+/// Gets system time in microseconds
+pub fn micros() -> u64 {
+    riscv::interrupt::free(|| {
+        unsafe {
+            // Latch timer value
+            write_reg(0xf000_380c, 1u32);
+            // Read timer value
+            let val: u32 = read_reg(0xf000_3810);
+            let val = 60_000_000 - val;
+            (SECONDS as u64 * 1_000_000) + (val as u64 / 60)
+        }
+    })
+}
+
+pub fn busy_wait_ms(ms: u32) {
+    let start = millis();
+    while millis() - start < ms {
+        unsafe {
+            asm!("nop");
+        }
+    }
+}
+
+pub fn busy_wait_us(us: u64) {
+    let start = micros();
+    while micros() -  start < us {
+        unsafe {
+            asm!("nop");
+        }
+    }
+}