I am considering a simple, low cost logging dongle for use in harsh environments:
HW
- uProc with UART
- RS-232 transceiver (max232)
- USB and Serial connectors
- regulator
- 1Mbyte SPI flash
- Marcell recommends MMC. In an epoxy-potted case it can be soldered without a socket. I only saw retail prices for larger MMCs. The 1M byte Sflash was melf or Sso8 package and $5 in 100 piece quantities and thus my interest. Does anyone have cost #s and sources for MMC? I figure a reasonable logging set at a good rate should yield 40 to 60 minutes at 1MByte of storage. Do we need more (as I think MMCs are much larger)?
Software
- Identify VEMS when attached and issue data dump requests - log resulting data stream
- Accepts commands when connected to host (PC or PDA) to dump data
- On board USB rechargable coin cell or host powered (5V on VEMS DB9 or USB on PC/PDA)
Conclusion
BoM, board, assembly and testing = cheap
Firmware = easy
Podded in epoxy = ruggedness
Anyone interested, please chime in. Cost for members should be kept in the $20 range.
Notes
- The group effort has (long-pending) plans on the following:
- firmware support for v3.x MMC logging GenBoard/LoggerIntegration is a bit confusing. See GenBoard/LoggerIntegration/MMC
- arm-boost is the codename of the low-cost (no fancy connectors) potted board (under development; 90 ARM uC-s are ordered for it and come in 2006 March) that is mostly sensing / networking / logging (but very restricted when it comes to power outputs). Useful for surprisingly many applications, logging is one. I suggest you join the development - first the MMC firmware _code_ than this.
- It's possible to roll an even smaller board (than arm-boost, perhaps with a different uC to save another $1 with only $900 of development task) but probably only justified if >500 can be sold.
I have no C skills and do not have the tools to contribute to the above (schematic or layout). It is less time for me to generate it in assembler and Orcad. My path will use Cygnal C8051F320 as I have the tools, can code the 8051 assembler, it has UART and USB on board as well as all the clock stuff. The BoM becomes USB connector, 320, Sflash, Vreg (Sot23), RS-232 level shifter and DB-9. There will be a few caps thrown in for the level shifter and regulator. No need for others to support software or hardware design. I can do schematics and layout in Orcad in my sleep (I am not good, it is just too easy). If interested, it can be for the group only as a development tool. There is no need to produce it (or have it meet production criteria). I will probably have to do this anyway for my work.