Digital potentiometer X9C104P with a Raspberry Pi 5

Question

I've tried using a Raspberry Pi 5 to control a digital potentiometer X9C104P. I followed this wiring diagram:

Potentiometer (POT) - Raspberry Pi

1. INC: GPIO20
2. UD: GPIO21
3. Vh: 5V
4. Vss: GND
5. Vcc: 5V
6. CS: GPIO16
7. Vl: GND
8. Vw: LED

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Implemented the provided code:

import tkinter as tk
import spidev

# Configuration du SPI (bus série)
spi = spidev.SpiDev()
spi.open(1, 2)  # Bus SPI 1, périphérique 2 (CE2)
spi.max_speed_hz = 1000000  # Vitesse de communication (1 MHz)

# Fonction pour ajuster la position du curseur
def adjust_potentiometer(direction):
    current_position = spi.xfer2([0x00])[0]
    if direction == "up":
        new_position = min(current_position + 1, 127)
    elif direction == "down":
        new_position = max(current_position - 1, 0)
    else:
        return
    spi.xfer2([0x80 | new_position])

# Création de l'interface Tkinter
root = tk.Tk()
root.title("Contrôle du Potentiomètre X9C104P")

# Boutons pour ajuster le potentiomètre
btn_up = tk.Button(root, text="Augmenter", command=lambda: adjust_potentiometer("up"))
btn_down = tk.Button(root, text="Diminuer", command=lambda: adjust_potentiometer("down"))

# Placement des boutons dans la fenêtre
btn_up.pack()
btn_down.pack()

# Boucle principale Tkinter
root.mainloop()

# Fermeture du bus SPI
spi.close()

However, the obtained result is that both buttons have the same effect: they increase the resistance, which decreases the brightness. Unfortunately, I couldn't manage to decrease the resistance.

Thank you for your help, I'm really stuck.

Answer 1

Try adding this:

define the following variable:

alt_position = current_position + 1

replace new_position variable definition in the "up" if statement in the function adjust_potentiometer

if not alt_position > 127:
  alt_position += 1
elif alt_position > 127:
  alt_position -= 1

and for new_position's "down" if statement:

if not alt_position < 0:
  alt_position -= 1
elif alt_position < 0:
  alt_position +=1

Comment if you have questions. Hope this helps!