=== Formula ===
* calculation of resistance R_LED_R :
<codemath>$R_{LEDR} = \sum_{n=0}^\infty a_n x^n</math> <math>\sum_{n=1}^{+\infty}\frac{1}{n^2}=\frac{\pi^2}{6}.</math> = \frac{U_r}{I} = \frac{VDD - U_{LR}}{I} = \frac{3.3V - 1.8V}{10mA} <math>0</math> = ''' 150 ohm '''$</code>
* power dispersed by the resistance P_R_LED_R :
<code>$<math>\frac{R_LED_R^{2}}{I} = \frac{150 o ^{2}}{10mA}</math> = ''' 15 mW ''' $</code>