example and basic readme

examples/counter.rs

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+//! Count how many times the device has been reset
+
+#![no_std]
+#![no_main]
+
+use xtensa_lx106_rt::entry;
+
+use core::fmt::Write;
+use core::panic::PanicInfo;
+use esp8266_flash::ESPFlash;
+use esp8266_hal::prelude::*;
+use esp8266_hal::target::Peripherals;
+use spi_memory::prelude::*;
+
+#[entry]
+fn main() -> ! {
+    // The default clock source is the onboard crystal
+    // In most cases 40mhz (but can be as low as 2mhz depending on the board)
+    // Clock speed is then doubled from the crystal frequency
+    let clock_frequency = 80.mhz();
+
+    let dp = unsafe { Peripherals::steal() };
+    let pins = dp.GPIO.split();
+    let mut led = pins.gpio2.into_push_pull_output();
+    let (mut timer1, _) = dp.TIMER.timers(clock_frequency);
+
+    let mut serial = dp
+        .UART0
+        .serial(pins.gpio1.into_uart(), pins.gpio3.into_uart());
+    let mut flash = ESPFlash::new(dp.SPI0);
+
+    const ADDR: u32 = 0x7E000;
+
+    timer1.delay_ms(1000);
+
+    led.set_high().unwrap();
+
+    let mut buff = [0u8; 8];
+
+    flash.read(ADDR, &mut buff).unwrap();
+
+    buff[0] += 1;
+
+    flash.erase_sectors(ADDR, 1).unwrap();
+
+    flash.write_bytes(ADDR, &mut buff).unwrap();
+
+    let _ = write!(&mut serial, "counter {}:\r\n", buff[0]);
+
+    loop {}
+}
+
+/// Basic panic handler - just loops
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    loop {}
+}