1 files changed, 93 insertions, 0 deletions
diff --git a/boiler-monster/stm32/app/ds1820.c b/boiler-monster/stm32/app/ds1820.c
new file mode 100644
index 0000000..200f4b7
--- /dev/null
+++ b/boiler-monster/stm32/app/ds1820.c
@@ -0,0 +1,93 @@
+#include "project.h"
+
+#define DS1820_READ_SCRATCHPAD 0xbe
+#define DS1820_CONVERT_T 0x44
+
+
+#define TIMEOUT 150
+
+
+
+static unsigned extract_leu16 (uint8_t *d)
+{
+  uint32_t u;
+
+  u = (uint32_t) d[0] | (((uint32_t) d[1]) << 8);
+  return u;
+}
+
+
+
+static int extract_les16 (uint8_t *d)
+{
+  uint32_t u;
+  u = extract_leu16 (d);
+
+  if (u & 0x8000) u |= 0xffff0000;
+
+  return (int) u;
+}
+
+
+
+
+
+static int
+ds1820_read_sp (const Onewire_addr *a, unsigned page, uint8_t *buf, unsigned len)
+{
+  if (onewire_reset_and_select (a))
+    return ~0U;
+
+  onewire_write_byte (DS1820_READ_SCRATCHPAD);
+  onewire_read_bytes (buf, len);
+
+  if ((len == 9) && onewire_check_crc (buf, 8, buf[8]))
+    return ~0U;
+
+  return 0;
+}
+
+
+
+static int ds1820_convert_t (const Onewire_addr *a)
+{
+
+  if (onewire_reset_and_select (a))
+    return ~0U;
+
+  onewire_write_byte (DS1820_CONVERT_T);
+
+  if (onewire_wait_complete (TIMEOUT))
+    return ~0U;
+
+  return 0;
+}
+
+int
+ds1820_read (const Onewire_addr *a, int *temp)
+{
+  uint8_t buf[9];
+  int t;
+
+  if (ds1820_read_sp (a, 0, buf, 9))
+    return 1;
+
+  if (ds1820_convert_t (a))
+    return 1;
+
+  if (ds1820_read_sp (a, 0, buf, 9))
+    return 1;
+
+  t = extract_les16 (&buf[0]);
+
+  t <<= 4 ;
+
+  if (temp)
+    *temp = t;
+
+
+  return 0;
+}
+
+
+