Sending data from Phone to arduino via BLE

Can data be sent from a smart phone to nano 33 BLE via BLE? Are there any forums/tutorials I could follow for such a sketch?

Depends how much data you want to send.
My paid pfodApp will send numbers/text from sliders/text input screens.
The free pfodDesigner will generate the Arduino sketch for you to display the menu you design, all the code is in the Arduino sketch.
See Arduino NANO 33 Made Easy for example sketches. might be another alternative.

So, for my specific use case, the data will consist of a TinyML model. Swift/ios has apis for connecting to BLE devices, and I'm certain android does too. If I setup an mobile application on either platform to communicate with a nano 33 BLE, can I transmit the model to the peripheral device and if it provides, can I transfer the model back to a mobile phone?

In that case neither of my suggestions are appropiate :frowning:

That doesn't mean it is infeasible, yea?

out of my experience.

Did you try the examples that come with the ArduinoBLE library?
They have all you need to get started. You will need to do some packaging and error handling on the application layer. The typical use case for BLE does not require every packet to be received. If a packet is lost for a temperature sensor the data will not update for one interval and no harm will be done in most cases.
By creating smart characteristics this robustness can be applied to many other use cases but not in your case. If part of the model is missing it will not work.
By adding a byte or two to your characteristic you can include a packet counter. This will allow you to detect if any packets are missing. You can then re-transmit the missing data.

Yea I thought of that too, As a second layer of protection against packet loss, I decided to transmit an "Acknowledging" packet when a packet is received. I'm assuming this will slow down the process?