SI5351 Micropython library

This repo contains another of my adaptations of the Adafruit SI5351 library at https://github.com/adafruit/Adafruit_Si5351_Library. This time it is for Micropython.

Simple Example

Import the library into your Micropython code to gain access to the SI5351 over I2C.

The below example sets the SI5351 clock output 0 to 13.703704 MHz.

from machine import Pin, I2C
import si5351

PIN_SCL = 5
PIN_SDA = 4

i2c = I2C(-1, Pin(PIN_SCL), Pin(PIN_SDA))

si = si5351.SI5351_I2C(i2c)

# vco = 25 MHz * (24 + 2 / 3) = 616.67 MHz
si.setupPLL(si.PLL_A, 24, 2, 3)

# out = 616.67 MHz / 45 = 13.703704 MHz 
si.setupMultisynth(0, si.PLL_A, 45)

# uncomment to divide 13.703704 by 64
# si.setupRdiv(0, si.R_DIV_64)

si.enableOutputs(True)

The set_freq() method

I also added a method called set_freq. This function calculates and sets the multisynth and R dividers based on the current VCO frequency of the PLL in use. It only works for frequencies below about 100Mhz.

Here is an example:

...
# vco = 25 MHz * 32 = 800 MHz
si.setupPLL(si.PLL_A, 32)

# set clk 0 to 7 Mhz based on the above vco
si.set_freq(clk, si.PLL_A, 7000000)

si.enableOutputs(True)

ESP8266 VFO Example

The next example is an implementation of a VFO using the SI5351. It was designed for the Heltec ESP8266 WIFIKIT Version A and it is provided in the repo as example.py.

To use the VFO, attach a rotary knob to GPIO pins 12 and 13 of the WIFIKIT. Next connect GPIO pins 4 and 5 for SDA and SCL to the same I2C pins on the SI5351. When the code first starts clk 0 will output 7Mhz. Turning the knob will change the clk 0 frequency in 10 Hz steps.

from machine import Pin, I2C
from si5351 import SI5351_I2C
from ssd1306 import SSD1306_I2C
import time

def latch2(p0, p1):
    a, b = p0.value(), p1.value()
    while True:
        a_last, b_last = a, b
        time.sleep_us(10)
        a, b = p0.value(), p1.value()
        if a == a_last and b == b_last: return a, b

class Encoder:
    """
      ---     ---     ---            ---     ---     ---
     |   |   |   |   |   |     A    |   |   |   |   |   |  
    -     ---     ---     -        -     ---     ---     --
    ---     ---     ---                ---     ---     ---
       |   |   |   |   |       B      |   |   |   |   |   | 
        ---     ---     ---        ---     ---    ---  
          Turn Left                       Turn right
          A 1 1 0 0 1                     A 1 1 0 0 1
          B 1 0 0 1 1                     B 0 1 1 0 0
    """

    def __init__(self, pina, pinb, handler):
        self.pina = pina
        self.pinb = pinb
        self.handler = handler
        self.position = 0
        self.last_a = latch2(self.pina, self.pinb)[0]
        self.pina.irq(trigger=Pin.IRQ_RISING | Pin.IRQ_FALLING, handler=self.ontrigger)

    def ontrigger(self, *args):
        a, b = latch2(self.pina, self.pinb)
        if a == 1 and self.last_a == 0:
            self.position += 1 if a == b else -1
            self.handler(self.position)
        self.last_a = a

# gpio pins

PIN_SCL = 5
PIN_SDA = 4
PIN_A   = 13
PIN_B   = 12
PIN_C   = 14

# constants

center = 7000000
mult = 32
clk = 0

# functions

def onchange(value):
    freq = center + value * 10
    oled.fill(0)
    oled.text('{:d} Hz'.format(freq), 0, 0)
    oled.show()
    si.set_freq(clk, si.PLL_A, freq)

# i2c bus

i2c = I2C(-1, Pin(PIN_SCL), Pin(PIN_SDA))

# oled

oled = SSD1306_I2C(128, 32, i2c)

# si5351 frequency generator

si = SI5351_I2C(i2c)
si.setupPLL(si.PLL_A, mult)
onchange(0)
si.enableOutputs(True)

# rotary encoder

Encoder(Pin(PIN_A, Pin.IN, Pin.PULL_UP), 
        Pin(PIN_B, Pin.IN, Pin.PULL_UP),
        onchange)

while True:
   pass

ESP32 BLE VFO Example

Script example32.py does the same thing as the prior example but the frequency can also be set and read using bluetooth. Connect to the bluefo device using the nRF Connect app.