Commit 19426850 authored by Per's avatar Per

bare6

parent ccddbada
......@@ -10,26 +10,56 @@ extern crate stm32f40x;
#[macro_use]
extern crate cortex_m_debug;
use stm32f40x::{DWT, GPIOA, RCC};
use stm32f40x::{DWT, GPIOA, GPIOC, RCC};
fn main() {
ipln!("init");
let dwt = unsafe { &mut *DWT.get() }; // get the reference to DWD in memory
let rcc = unsafe { &mut *RCC.get() }; // get the reference to RCC in memory
let gpioa = unsafe { &mut *GPIOA.get() }; // get the reference to GPIOA in memory
let gpioc = unsafe { &mut *GPIOC.get() }; // get the reference to GPIOC in memory
dwt.enable_cycle_counter();
clock_out(rcc, gpioc);
idle(dwt, rcc, gpioa);
}
// uses the DWT.CYCNT
// doc: ARM trm_100166_0001_00_en.pdf, chapter 9.2
// we use the `cortex-m` abstraction
// we use the `cortex-m` abstraction, as re-exported by the stm32f40x
fn wait_cycles(dwt: &mut DWT, nr_cycles: u32) {
let t = dwt.cyccnt.read().wrapping_add(nr_cycles);
while (dwt.cyccnt.read().wrapping_sub(t) as i32) < 0 {}
}
// see the Reference Manual RM0368 (www.st.com/resource/en/reference_manual/dm00096844.pdf)
// rcc, chapter 6
// gpio, chapter 8
fn clock_out(rcc: &mut RCC, gpioc: &mut GPIOC) {
// output MCO2 to pin PC9
// mco2 : SYSCLK = 0b00
// mcopre : divide by 4 = 0b110
rcc.cfgr
.modify(|_, w| unsafe { w.mco2().bits(0b00).mco2pre().bits(0b110) });
// power on GPIOC, RM0368 6.3.11
rcc.ahb1enr.modify(|_, w| w.gpiocen().set_bit());
// MCO_2 alternate function AF0, STM32F401xD STM32F401xE data sheet
// table 9
// AF0, gpioc reset value = AF0
// configure PC9 as alternate function 0b10, RM0368 6.2.10
gpioc.moder.modify(|_, w| unsafe { w.moder9().bits(0b10) });
// otyper reset state push/pull, in reset state (don't need to change)
// ospeedr 0b11 = high speed
gpioc
.ospeedr
.modify(|_, w| unsafe { w.ospeedr9().bits(0b11) });
}
// user application
fn idle(dwt: &mut DWT, rcc: &mut RCC, gpioa: &mut GPIOA) {
ipln!("idle");
......@@ -53,3 +83,80 @@ fn idle(dwt: &mut DWT, rcc: &mut RCC, gpioa: &mut GPIOA) {
wait_cycles(dwt, 8000_000);
}
}
// 1. compile and run the example, in 16Mhz
// the processor SYSCLK defaults to HCI 16Mhz
// (this is what you get after a `monitor reset halt`)
//
// confirm that your ITM dump traces the init, idle and led on/off
// make sure your TPIU is set to a system clock at 16Mhz
//
// you may use either ITM tracing using ITM dump or internally in
// vscode using the new "cortex debug" plugin
//
// what is the frequency of blinking
// ** your answer here **
//
// commit your answers (bare6_1)
//
// 2. now connect an oscilloscope to PC9, which is set to
// output the MCO2
//
// what is the frequency of MCO2 read by the oscilloscope
// ** your answer here **
//
// compute the value of SYSCLK based on the oscilloscope reading
// ** your answer here **
//
// what is the peak to peak reading of the signal
// ** your answer here **
//
// make a folder called "pictures" in your git project
// make a screen dump or photo of the oscilloscope output
// sove the the picture as "bare_6_16mhz_high_speed"
//
// commit your answaaasers (bare6_2)
//
// 3. now run the example in 64Mz
// you can do that by issuing a `monitor reset init`
// which reprograms SYSCLK to 4*HCI
// (make sure you have the latest openocd v 0.10)
//
// confirm that your ITM dump traces the init, idle and led on/off
// (make sure your TPIU is set to a system clock at 64Mhz)
//
// what is the frequency of blinking
// ** your answer here **
//
// commit your answers (bare6_3)
//
// 4. repeat the experiment 2
// what is the frequency of MCO2 read by the oscilloscope
// ** your answer here **
//
// compute the value of SYSCLK based on the oscilloscope reading
// ** your answer here **
// what is the peak to peak reading of the signal
//
// ** your answer here **
//
// make a screen dump or photo of the oscilloscope output
// sove the the picture as "bare_6_64mhz_high_speed"
//
// commit your answers (bare6_4)
//
// 5. now reprogram the PC9 to be "Low Speed", and re-run at 64Mz
//
// did the frequency change in comparison to assignment 4.
// ** your answer here **
//
// what is the peak to peak reading of the signal
// ** your answer here **
//
// why does it differ?
// ** your answer here **
//
// make a screen dump or photo of the oscilloscope output
// sove the the picture as "bare_6_64mhz_low_speed"
//
// commit your answers (bare6_24)
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