diff --git a/stm-firmware/calibration.c b/stm-firmware/calibration.c
index 489e8f4..1b00983 100644
--- a/stm-firmware/calibration.c
+++ b/stm-firmware/calibration.c
@@ -75,6 +75,71 @@ free_mem:
 	return NULL;
 }
 
+static float calculate_mean(float *values, uint32_t count)
+{
+	uint32_t loop_cnt = (count + 7) / 8;
+	uint32_t remainder = count % 8;
+	float sum = 0;
+
+	switch (remainder) {
+	case 0: do { sum += *values++; /* FALLTHRU */
+	case 7:      sum += *values++; /* FALLTHRU */
+	case 6:      sum += *values++; /* FALLTHRU */
+	case 5:      sum += *values++; /* FALLTHRU */
+	case 4:      sum += *values++; /* FALLTHRU */
+	case 3:      sum += *values++; /* FALLTHRU */
+	case 2:      sum += *values++; /* FALLTHRU */
+	case 1:      sum += *values++;
+		} while (--loop_cnt > 0);
+	}
+
+	return sum/(float)count;
+}
+
+static float calculate_standard_deviation(float *values, uint32_t count, float mean)
+{
+	uint32_t loop_cnt = (count + 7) / 8;
+	uint32_t remainder = count % 8;
+	float sum = 0;
+	float res;
+
+	switch (remainder) {
+	case 0: do { sum += (*values - mean) * (*values - mean);
+			values++;
+			/* FALLTHRU */
+	case 7:      sum += (*values - mean) * (*values - mean);
+			values++;
+			     /* FALLTHRU */
+	case 6:      sum += (*values - mean) * (*values - mean);
+			     values++;
+			     /* FALLTHRU */
+	case 5:      sum += (*values - mean) * (*values - mean);
+			     values++;
+			     /* FALLTHRU */
+	case 4:      sum += (*values - mean) * (*values - mean);
+			     values++;
+			     /* FALLTHRU */
+	case 3:      sum += (*values - mean) * (*values - mean);
+			     values++;
+			     /* FALLTHRU */
+	case 2:      sum += (*values - mean) * (*values - mean);
+			     values++;
+			     /* FALLTHRU */
+	case 1:      sum += (*values - mean) * (*values - mean);
+			     values++;
+			     /* FALLTHRU */
+		} while (--loop_cnt > 0);
+	}
+
+	sum /= (float)count;
+	/* Compute the square roor using the FPU.
+	 * The constraint 't' tells GCC to use a floating point register
+	 */
+	__asm__ __volatile__("vsqrt.f32 %0, %1" : "=t"(res) : "t"(sum));
+
+	return res;
+}
+
 static int calibration_poll_data_acquisition(float *mem_array, uint32_t count, volatile int *flag, float *mu, float *max_dev)
 {
 	int ret_val = 0;
@@ -99,10 +164,9 @@ static int calibration_poll_data_acquisition(float *mem_array, uint32_t count, v
 	/* Convert the stream memory to Ohm readings */
 	adc_pt1000_convert_raw_value_array_to_resistance(NULL, mem_array, count);
 
-	/* Do not compute std-deviation. Too imprecise
-	 * arm_std_f32(stream_mem, count, sigma);
-	 */
-	arm_mean_f32(mem_array, count, mu);
+	/* Do not compute std-deviation. Too imprecise */
+	*mu = calculate_mean(mem_array, count);
+	*max_dev = calculate_standard_deviation(mem_array, count, *mu);
 
 	/* Find min and max values of array */
 	for (i = 0U; i < count; i++) {
@@ -111,7 +175,7 @@ static int calibration_poll_data_acquisition(float *mem_array, uint32_t count, v
 	}
 
 	/* Compute maximum deviation range */
-	*max_dev = max_val - min_val;
+	//*max_dev = max_val - min_val;
 
 ret_free_mem:
 	free(mem_array);