update readme with some basics

README.md

@@ -1,3 +1,32 @@
 # STM32-DS2482-HAL
 
-A DS2482-100 HAL for the STM32F3 series
+A DS2482-100 HAL for the STM32F3/F4/H7 series
+
+## Usage
+
+Be sure to have the target chip defined:
+
+`gcc [...] -DSTM32[F3/F4/H7]`
+
+or
+```yaml
+# (in STM32-for-VSCode.config.yaml)
+# Compiler definitions. The -D prefix for the compiler will be automatically added.
+cDefinitions:
+  - STM32[F3/F4/H7]
+  - USE_HAL_DRIVER
+```
+
+Then, configure the HAL:
+
+```c
+// (in DS2482_HAL.h)
+#define DS2482_I2C_ADDR 0x30  //change to desired values
+#define DS2482_TIMEOUT_1W 100 //how long we wait for 1-Wire operations to complete
+#define DS2482_TIMEOUT_I2C 100
+```
+
+Call `ds2482_init()` with the I2C handle, and the HAL is ready.
+
+Be sure to check the return values for error handling.
+