Stm32f303 target speed trivial check (#66)

* Check new I2C target_speed config setting

* Corrected incorrect doc comment

src/core/i2c.zig

@@ -148,8 +148,7 @@ pub const Pins = struct {
     sda: ?type = null,
 };
 
-/// A UART configuration. The config defaults to the *8N1* setting, so "8 data bits, no parity, 1 stop bit" which is the
+/// An I2C configuration.
-/// most common serial format.
 pub const Config = struct {
     /// The target speed in bit/s. Note that the actual speed can differ from this, due to prescaler rounding.
     target_speed: u32,

src/modules/chips/stm32f303/stm32f303.zig

@@ -274,8 +274,6 @@ pub fn I2CController(comptime index: usize, comptime pins: micro.i2c.Pins) type
         const Self = @This();
 
         pub fn init(config: micro.i2c.Config) !Self {
-            // TODO: use config
-            _ = config;
             // CONFIGURE I2C1
             // connected to APB1, MCU pins PB6 + PB7 = I2C1_SCL + I2C1_SDA,
             // if GPIO port B is configured for alternate function 4 for these PB pins.
@@ -307,6 +305,7 @@ pub fn I2CController(comptime index: usize, comptime pins: micro.i2c.Pins) type
             // 4-6. Configure I2C1 timing, based on 8 MHz I2C clock, run at 100 kHz
             // (Not using https://controllerstech.com/stm32-i2c-configuration-using-registers/
             // but copying an example from the reference manual, RM0316 section 28.4.9.)
+            if (config.target_speed != 100_000) @panic("TODO: Support speeds other than 100 kHz");
             regs.I2C1.TIMINGR.modify(.{
                 .PRESC = 1,
                 .SCLL = 0x13,