ADC conversion and DMA

Setup ADC conversions to happen automatically, transferring results to a buffer
using DMA, also set up channel injection, where instead the tip temperature is
read sinchronously

fw/lincal.h

@@ -0,0 +1,22 @@
+#ifndef _LINCAL_H
+#define _LINCAL_H
+
+#include <ch32fun.h>
+
+
+// Fixed-point number in 8.8 format
+typedef int16_t fp16_t;
+#define F32_TO_FP16(f) ((fp16_t)((f) * 256.0f))
+
+// Intger part of fp16_t
+#define I(f) ((f) >> 8)
+// Decimal part of fp16_t
+#define D(f) ((f) & 0xFF)
+
+// v * a + b for signed 16-bit
+#define I16_LINCAL(v, a, b) ((int16_t)((((int32_t)(v) * (a)) >> 8) + (b)))
+// v * a + b for unsigned 16-bit
+#define U16_LINCAL(v, a, b) ((uint16_t)((((uint32_t)(v) * (a)) >> 8) + (b)))
+
+
+#endif