Specification questions

Alec posted Nov 10, 2020:

Hi. I have some questions about the notecard:

1- What is the memory size for the notes queues
2- What is the memory size of the host firmware
3- What is the accuracy of the onboard temperature sensor
4- What is the accuracy of the onboard voltage monitor


@bsatrom posted Nov 11, 2020:

Hey Alec thanks for the question! Let me dig up answers on these and I’ll get back to you.

@bsatrom posted Nov 12, 2020:

@Alec, a few answers for you:

  1. Memory Size for Notes - The Notecard provides approx. 900KB of non-volatile storage for Notefiles. This is cumulative across user Notefiles and the size of an individual file depends on the number of Notes, and whether those are raw JSON notes, or templated notes

  2. Memory Size of Host Firmware - If you are referring to the STM32 processor on the Notecard, that codespace is not developer-accessible, so we don’t disclose the size of the main firmware. If you’re referring to the size of a MCU Host binary that can be downloaded from Notehub to the Notecard, the limit is approx. 700KB.

  3. Accuracy of the onboard temp sensor - For the specifics on this one, I’ll refer you to the datasheet for the LIS2DW12 which we use as both an accelerometer and temperature sensor. And as an additional FYI, the card.wireless request includes a calibration value in the response that indicates the amount we’ve chosen to offset the raw reading based on real-world usage and testing. For example:


The value is the calibration-adjusted temperature, meaning that the sensor reads 3 degrees C higher

  1. Accuracy of onboard voltage monitor - We measure voltage using an ADC with 10-bit resolution. That said, the monitor is pre-calibrated under the assumption that between the supply and the V+ pin there is a single FSV1045V Ultra-Low VF Schottky diode, which we include on all Notecarriers. If you’re building a custom carrier board and need to use a different type of diode with a different forward voltage drop, you can adjust calibration by using the “calibration” argument on card.voltage.