initial modem setup (pins, serial, power...)

src/main.rs

@@ -3,19 +3,63 @@
 
 use esp_backtrace as _;
 use esp_println::println;
-use hal::{clock::ClockControl, peripherals::Peripherals, prelude::*, Delay};
+use hal::{
+    clock::ClockControl,
+    gpio::{IO},
+    peripherals::Peripherals,
+    prelude::*,
+    prelude::nb::block,
+    Delay,
+    uart::{
+        TxRxPins,
+        config::{
+            Config,
+            Parity,
+            StopBits,
+            DataBits,
+        },
+        Uart,
+    }
+};
 
 #[entry]
 fn main() -> ! {
     let peripherals = Peripherals::take();
-    let system = peripherals.DPORT.split();
+    let mut system = peripherals.DPORT.split();
     let clocks = ClockControl::boot_defaults(system.clock_control).freeze();
     let mut delay = Delay::new(&clocks);
 
-    println!("Hello world!");
+    let io = IO::new(peripherals.GPIO, peripherals.IO_MUX);
 
+    // LilyGo A7670E serial pins.
+    // LilyGo TTGO T-Call sim800l board power / reset pins.
+    let modem_uart_pins = TxRxPins::new_tx_rx(
+        io.pins.gpio26.into_push_pull_output(),
+        io.pins.gpio27.into_floating_input(),
+    );
+
+    let config = Config {
+        baudrate: 115200,
+        data_bits: DataBits::DataBits8,
+        parity: Parity::ParityNone,
+        stop_bits: StopBits::STOP1,
+    };
+
+    // UART interface for the GSM modem
+    let mut serial = Uart::new_with_config(
+        peripherals.UART1,
+        Some(config),
+        Some(modem_uart_pins),
+        &clocks,
+        &mut system.peripheral_clock_control,
+    );
+
+    println!("Start");
     loop {
-        println!("Loop...");
-        delay.delay_ms(500u32);
+        serial.write(0x42).ok();
+        let read = block!(serial.read()).unwrap();
+        println!("{}", read);
+
+        delay.delay_ms(1000_u32);
     }
 }