1 files changed, 38 insertions, 0 deletions
diff --git a/center_fw/volt_div.py b/center_fw/volt_div.py
new file mode 100644
index 0000000..85b511a
--- /dev/null
+++ b/center_fw/volt_div.py
@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+
+
+def calc_output(v_c1, v_c2):
+    vref = 3.3 / 2 # [V]
+    rref = 1/(1/10e3 + 1/10e3) # [Ohm]
+
+    vpos = vref + (v_c1 - vref) * rref / (rref + 220e3)
+
+    # vneg = vdiff + (v_c2 - vdiff) * 10e3 / (220e3 + 10e3)
+    # vneg =!= vpos
+    k1 = rref / (rref + 220e3)
+    k2 = 10e3 / (220e3 + 10e3)
+    # vdiff + (v_c2 - vdiff) * k2 = vref + (v_c1 - vref) * k1
+    # vdiff + v_c2*k2 - vdiff*k2 = vref + (v_c1 - vref) * k1
+    # vdiff * (1-k2) = vref + (v_c1 - vref)*k1 - v_c2*k2
+    vdiff = (vref + (v_c1 - vref)*k1 - v_c2*k2) / (1-k2)
+    adc_counts = vdiff / 3.3 * 0xffff
+    print(f'{vdiff:.3f} V ^= {round(adc_counts)} counts')
+    return adc_counts
+
+print('Results for 18 V')
+a = calc_output(18, 0)
+b = calc_output(0, 18)
+print(f'middle = {round((b+a)/2)} counts')
+
+print()
+print('Results for 24 V')
+a = calc_output(24, 0)
+b = calc_output(0, 24)
+print(f'middle = {round((b+a)/2)} counts')
+
+for v in range(11, 25):
+    print()
+    print(f'Results for {v} V with 0.7 V diode drop on GND')
+    a = calc_output(v-0.7, -0.7)
+    b = calc_output(-0.7, v-0.7)
+    print(f'middle = {round((b+a)/2)} counts')