IMU data logger brain storm - Page 1
Forum section: electronics / projects

author: pmd
author_rank: Newbie
timestamp: May 30, 2017, 05:37:05 pm
content: Hello,This is my first post hereI would like to have a little brain storm with you about a new product that I'm currently designing.This is an IMU data logger that has to record IMU data to flash memory - 9 axis (16 bit x 10) at 100Hz rate.The device has to record for 3 hours minimum, it has to be battery powered, very small and data download has to be very easy.My first brain storm -What MCU do i choose, STM, Atmel, NXP, Cypress? The parameters are - cost, performance, development environment, size, battery life8 bit or 32 bit MCU?Part 2:I have to download data from multiple (24) loggers, so I'm going to design some kind of docking station for 24 units that will charge the units and download the data (32MB each) to PCSecond brain storm -Should I add USB for each device and design the docking station as USB hub, this way each device will show up on the PC as USB driveorShould I use UART/SPI/I2C interface between unit and docking station and the docking station will connect to the PC as COM port?Any input will be appreciatedThanksMichael

author: krho
author_rank: Regular Contributor
timestamp: May 30, 2017, 07:58:59 pm
content: stm32l0 or stm32l4, qspi for datastorage and USB for communication/charging.

author: thm_w
author_rank: Super Contributor
timestamp: May 31, 2017, 11:23:58 pm
content: Quote from: pmd on May 30, 2017, 05:37:05 pmI would do this. If its not a problem for user to open 24 drives and cut and paste the data. Or you could automate this.Data rate about 2kB/s right? Thats easily done with microSD, 1-bit data.32MB is on the edge of serial flash (largest size), but IMO microSD is nice because you can swap it out easily and manually download if needed. If you are certain you would not need more than 32MB, a serial flash chip would be the smallest solution. You can see some data in my report under "4.7 External storage", it might be relevant (https://hackaday.io/project/21912-portable-air-quality-monitor#menu-detailsfile is portable_air_quality.pdf).I used STML476, but that would be too expensive. For sure you can get away with a lower cost chip. I didn't implement mounting FatFS over USB, but should be doable.

author: Kalvin
author_rank: Super Contributor
timestamp: June 01, 2017, 06:08:29 am
content: Quote from: blueskull on May 31, 2017, 09:43:27 pmIt might be worth taking a look at those patents as some of the patents regrading FAT has already been expired.

author: pmd
author_rank: Newbie
timestamp: June 01, 2017, 06:29:49 am
content: All, thank you for your replaysQuoteCan you explain more?I don't want to use SD card because it will be more expansive to add SD card holder and buy SD cards - I'm going to mass production. Also, the product is sealed and there wont be no access to remove SDI see that every body recommend STM32L (I also prefer STM), generally speaking why not Atmel or NXP?

author: thm_w
author_rank: Super Contributor
timestamp: June 01, 2017, 08:05:10 pm
content: Quote from: pmd on June 01, 2017, 06:29:49 amThen use the flash I mentioned, if there is space put a footprint for a second chip in case 32MB is not enough.

author: krho
author_rank: Regular Contributor
timestamp: June 01, 2017, 09:09:43 pm
content: QSPI flash in 8pin package goes up to 1Gbit => 128MiB