Good afternoon, and thank you for the opportunity to bid on your project!
I'm an experienced embedded systems designer with over 20 years' experience, although I've only just started on the Freelancer platform. Your project has some very aggressive constraints that I'd like to discuss with you.
I usually approach these projects with a milestone based approach, with the first milestone being the development of a comprehensive specifications document. With such a document in place we can both proceed more easily, as the development is very accurately described and we each understand and agree to them.
To that end, my primary concern is with the overall size of the board. The necessity of an external 16-bit codec (since you also want an analog output) and TCXO means that it's very unlikely that these three components along with their support circuitry will be a tight fit in a 3.5cm square. The routing may necessitate a 6 or even 8 layer board to meet this size requirement.
Please note that my proposal does not include the physical board, parts, nor assembly costs. I can recommend companies for these tasks or work with you in selecting companies to perform these tasks.
Thank you again for the opportunity. I look forward to discussing this project with you!
Regards,
Andrew