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Status Updates
Firmware is now in the repository, along with libraries. Note that the project still uses the Arduino build system, which means that the libraries must be copied/linked into your Arduino libraries directory.
The prototype was taken to the Connecticut River, and worked without a problem for 5 days of field work. So far, all the data coming back looks good. The RTC has proven itself accurate to 0.1 s/day.
battery pack: PCBs from SeeedStudio seem fine, and the one that has been soldered up with 6 CR123 holders is solid. Remaining issues are
- low-voltage protection? is it unsafe to drain lithium cells all the way to 0V?
- The original plan was to have the same hole layout as the Arduino Due. While the hole pattern for the Due isn't quite symmetric, it's close enough that it's difficult to have the battery pack holes not too close to the Due mounting holes. Ideally, move the existing four holes to clearly avoid the Due mounting holes, and add another pair of mounting holes near the middle since there will be some force inserting/removing batteries.
- choose a style of jack or header connector for the power cable joining the battery pack and the logger.
logger: the ADS1115 external ADC appears to work fine alongside SPI. The 3rd party I2C library for the Teensy works well, but out of the box it can only background a single operation at a time. Reading from the ADC requires several steps,
- write to the address register for the conversion result
- request 2 bytes from that register
- write to the config register to begin the next conversion.
- Wait a while.
With a few modifications, the I2C library can now call a user function when an operation completes, so steps 1-3 are chained together.
Running the ADC conversions off of a 500Hz timer interrupt, and logging to SD in the main "thread" appears to work without issue. So far only a DC 2.5V signal (from a discrete shunt reference) has been used, but over