From c994c3323ee1b0d19faa86ebe26a01d566b86eaa Mon Sep 17 00:00:00 2001
From: root <root@ka-ata-killa.ourano.james.local>
Date: Wed, 17 Feb 2021 18:33:49 +0000
Subject: stm8 humidity sensor

---
 humidity_sensors/app/awu.c   | 58 ++++++++++++++++++++------------------------
 humidity_sensors/app/main.c  |  8 +++---
 humidity_sensors/app/sht20.c | 31 +++++++++++++++++++++++
 3 files changed, 62 insertions(+), 35 deletions(-)

diff --git a/humidity_sensors/app/awu.c b/humidity_sensors/app/awu.c
index 18cf1f8..dc7ea9f 100644
--- a/humidity_sensors/app/awu.c
+++ b/humidity_sensors/app/awu.c
@@ -1,21 +1,19 @@
 #include "project.h"
 
 /** Contains the different values to write in the APR register (used by AWU_Init function) */
-CONST uint8_t APR_Array[17] =
-    {
-        0, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 61, 23, 23, 62
-    };
+CONST uint8_t APR_Array[17] = {
+  0, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 61, 23, 23, 62
+};
 
 /** Contains the different values to write in the TBR register (used by AWU_Init function) */
-CONST uint8_t TBR_Array[17] =
-    {
-        0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 12, 14, 15, 15
-    };
+CONST uint8_t TBR_Array[17] = {
+  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 12, 14, 15, 15
+};
 
 
-FlagStatus AWU_GetFlagStatus(void)
+FlagStatus AWU_GetFlagStatus (void)
 {
-  return((FlagStatus)(((uint8_t)(AWU->CSR & AWU_CSR_AWUF) == (uint8_t)0x00) ? RESET : SET));
+  return ((FlagStatus) (((uint8_t) (AWU->CSR & AWU_CSR_AWUF) == (uint8_t)0x00) ? RESET : SET));
 }
 
 
@@ -25,46 +23,42 @@ INTERRUPT_HANDLER (AWU_IRQHandler, 1)
 }
 
 
-void AWU_Init(AWU_Timebase_TypeDef AWU_TimeBase)
+void AWU_Init (AWU_Timebase_TypeDef AWU_TimeBase)
 {
   /* Enable the AWU peripheral */
   AWU->CSR |= AWU_CSR_AWUEN;
-  
+
   /* Set the TimeBase */
-  AWU->TBR &= (uint8_t)(~AWU_TBR_AWUTB);
-  AWU->TBR |= TBR_Array[(uint8_t)AWU_TimeBase];
-  
+  AWU->TBR &= (uint8_t) (~AWU_TBR_AWUTB);
+  AWU->TBR |= TBR_Array[ (uint8_t)AWU_TimeBase];
+
   /* Set the APR divider */
-  AWU->APR &= (uint8_t)(~AWU_APR_APR);
-  AWU->APR |= APR_Array[(uint8_t)AWU_TimeBase];
+  AWU->APR &= (uint8_t) (~AWU_APR_APR);
+  AWU->APR |= APR_Array[ (uint8_t)AWU_TimeBase];
 }
 
 
-void AWU_LSICalibrationConfig(uint16_t lsifreqkhz)
+void AWU_LSICalibrationConfig (uint16_t lsifreqkhz)
 {
   uint16_t A = 0x0;
-  
-  
+
+
   /* Calculation of AWU calibration value */
-  
-  A = (uint16_t)(lsifreqkhz >> 2U); /* Division by 4, keep integer part only */
-  
+
+  A = (uint16_t) (lsifreqkhz >> 2U); /* Division by 4, keep integer part only */
+
   if ((4U * A) >= ((lsifreqkhz - (4U * A)) * (1U + (2U * A))))
-  {
-    AWU->APR = (uint8_t)(A - 2U);
-  }
+    AWU->APR = (uint8_t) (A - 2U);
   else
-  {
-    AWU->APR = (uint8_t)(A - 1U);
-  }
+    AWU->APR = (uint8_t) (A - 1U);
 }
 
 
-void awu_init(void)
+void awu_init (void)
 {
 
-    AWU_LSICalibrationConfig(128);
-    AWU_Init(AWU_TIMEBASE_1S);
+  AWU_LSICalibrationConfig (128);
+  AWU_Init (AWU_TIMEBASE_1S);
 }
 
 
diff --git a/humidity_sensors/app/main.c b/humidity_sensors/app/main.c
index 6f15cdf..6c9e602 100644
--- a/humidity_sensors/app/main.c
+++ b/humidity_sensors/app/main.c
@@ -15,9 +15,11 @@ main (void)
   sht20_reset();
 
 
-  enableInterrupts ();
+  enableInterrupts();
 
   for (;;) {
+    sht20_setup();
+
     printf ("$SNTHD,%s,%s\n", sht20_temp_s(), sht20_humid_s());
 
     while (!uart_rx (&c)) {
@@ -25,8 +27,8 @@ main (void)
         sht20_reset();
     }
 
-    delay_ms(10);
+    delay_ms (10);
     halt();
-    delay_ms(10);
+    delay_ms (10);
   }
 }
diff --git a/humidity_sensors/app/sht20.c b/humidity_sensors/app/sht20.c
index d6d648b..5d6acb7 100644
--- a/humidity_sensors/app/sht20.c
+++ b/humidity_sensors/app/sht20.c
@@ -11,6 +11,13 @@
 #define SOFT_RESET                            0xFE
 
 
+#define MAX_RESOLUTION            ((u8) 0x00)
+#define BATTERY_LOW               ((u8) 0x40)
+#define RESERVED_MASK             ((u8) 0x38)
+#define ENABLE_HEATER             ((u8) 0x04)
+#define DISABLE_OTP_RELOAD        ((u8) 0x02)
+
+
 void
 sht20_reset (void)
 {
@@ -119,3 +126,27 @@ sht20_humid_s (void)
   return ret;
 
 }
+
+void sht20_setup (void)
+{
+  uint8_t u;
+
+  i2cb_start_transaction (SHT20_ADDRESS, I2C_WRITE);
+  i2cb_send_data (READ_USER_REG);
+  i2cb_start_transaction (SHT20_ADDRESS, I2C_READ);
+  u = i2cb_read (0);
+  i2cb_stop();
+
+
+  u &= RESERVED_MASK;
+  u |= MAX_RESOLUTION | DISABLE_OTP_RELOAD;
+
+  // FWIW - it appears to be impossible to turn off the heater
+  // with either a reset or write, perhaps a fake chip?
+  u &= ~ ENABLE_HEATER;
+
+  i2cb_start_transaction (SHT20_ADDRESS, I2C_WRITE);
+  i2cb_send_data (WRITE_USER_REG);
+  i2cb_send_data (u);
+  i2cb_stop();
+}
-- 
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