I've an embedded system (ARM cortex M0) which runs firmware and has USB mass storage with size 79kB. So when you plug in the device to any computer(MAC/Windows), it pops as a 79kB flash drive. The firmware creates files which has transaction records. The objective is to display these transactions (tables and simple graphs) to the user. I've narrowed down to a web browser. So the user (with MAC/Windows PC) can plug in the USB device mass storage and open an HTML file in the mass storage drive and view all the transactions in the form of tables and simple bar graphs. The tricky part comes here: the device(firmware) needs to update it's clock, and this time input has to be sourced from the MAC/Windows PC. How can this be achieved? This is the minimum requirement. Further, through the web browser the user wants to write some configuration parameters for e.g. through a text box and a submit button in the HTML page. NOTE: The USB mass storage class and the web browser approach were selected so that there is no prerequisites for the user. You can suggest alternatives if this can be done using another approach for e.g. a different class of USB or some other application locally available on MAC/Windows desktop/laptop.
Have them edit or create a text file on the drive.