Si5351 Clock Generator

[johnfheaton]

Hi: I have an Si5351 on order.
I simply want to generate 1MHz clock pulses.
Questions:
1. Do I need an Arduino to set up or remain connected to the Si5351?
2. If not, please advise how to set up the Si5351 to generate 1 MHz pulses.
Your help much appreciated.
Best regards
John H

[adafruit_support_carter]

In general, you need to talk to the SI5351 over I2C to tell it what to do. This will come down to setting various values in various registers to control the behavior and set the output frequency. All of the registers will reset to default values with a power cycle, so you would loose any configuration. So, I think the answers are:

1. Do I need an Arduino to set up or remain connected to the Si5351?

yes

2. If not, please advise how to set up the Si5351 to generate 1 MHz pulses.

see above

More info:
https://learn.adafruit.com/adafruit-si5 ... t/overview

[Level42]

I don't understand this.

I need a solution like this Adafruit clock generator for "stand alone" use. I would program it once and let it run in the "application".

On various threads here it is set the Si5351 will loose it's settings at power-cycle but the data sheet says this:

5. Configuring the Si5351
The Si5351 is a highly flexible clock generator which is entirely configurable through its I2C interface. The device’s default configuration is stored in non-volatile memory (NVM) as shown in Figure 11. The NVM is a one time programmable memory (OTP) which can store a custom user configuration at power-up. This is a useful feature for applications that need a clock present at power-up (e.g., for providing a clock to a processor).


Figure 11. Si5351 Memory Configuration
During a power cycle the contents of the NVM are copied into random access memory (RAM), which sets the device configuration that will be used during normal operation. Any changes to the device configuration after power-up are made by reading and writing to registers in the RAM space through the I2C interface. A detailed register map is shown in Section "8. Register Descriptions" on page 25.

This sounds like it _should_ run with the last programming after a power cycle ?

Also...what good is a clock generator that needs to be run with a Arduino or similar intelligent device ?

[Franklin97355]

Quotes from Si:

There is no way to modify the Si5351 NVM outside of the Silicon Labs manufacturing process, however you can create a custom NVM configuration using the Clock Builder software and Silicon Labs will manufacture custom Si5351 parts for you at no extra charge.
If production lead-times are a concern you should use a Si5351 device and program it with your custom configuration via I2C. This is the preferred option for fast prototyping, then locking down the configuration with burned OTP through Clock Builder for volume production.

You might check with Si to see how they recommend doing this.

[adafruit2]

yah thats not what we design/use it for - we have it so you need to configure it on boot each time.

[Level42]

.....which makes it a rather useless product..... a clock generator need to fire up as soon as you power up the device that it is supposed to clock.....weird.....

[Franklin97355]

A clock generator needs to output a precise clock frequency. If you need something different then this one is not for you but it is far from useless.

[Level42]

Excellent reply, reallly useful, thanks.