I am considering a simple, low cost logging dongle for use in harsh environments:
HW
- Cygnal C8051F320 uProc with UART
- Marcell recommends AT91SAM7A3
- RS-232 transceiver (RS-232 level shifter, max232)
- DSUB9 Serial connector
- USB connector
- Vreg (Sot23)
- 1Mbyte SPI flash Sflash (or MMC)
- 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.
- MMC/SD wholesale price starts from under $10. Marcell's source only sells in Hungary, but we can relay for you (even send you a few for free). Please confirm that SD card (SD must support SPI mode, while it is an option for MMC - though we heard that almost all MMC does support it too). I did a quick search for MMCs and found 32Mbyte cards for $15 discounted retail so wholesale volume pricing should be under $10. Also Silicon Systems (Cygnal) 8051 app note code written in C and thus might be portable enough to have someone with experience do it in the uproc of choice.
- attaching the card is very easy when it's potted and not removable anyway. Simply can be soldered (even pick-n-place would work, although that requires significant PCB space reserved compared to angled attach).
- If jumpered, it can reside on "solder side".
- Cygnal has app note with code for USB A/D logger using MMC. Good news is all the MMC stuff is done. The Serial stuff, if kept simple, is easy.
- Emil also votes for a MMC / SD card, even if 1Mbyte is a lot of logging, 64 meg would sell better.
- 320 short for F8051C320... I know you guys understand shorthand as I am constantly trying to figure out what you are talking about on the wiki (Ha Ha).
- There will be a few caps thrown in for the level shifter and regulator.
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)
- some sort of realtime clock, We need to be able to relate logging packets in time. Megatune adds realtime clock to it's logs on the pc.
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.
Bill's choice
- currently no C skills and do not have the tools to contribute to the above (schematic or layout).
- Note that anyone who programs assembly, C is very easy and fun, and a good investment (takes little time anyway). The tools are easy to install (eg. winavr is just a 1-click installer)
- I can do schematics and layout in Orcad in my sleep (I am not good, it is just too easy).
- It is less time for me to generate it in assembler and Orcad.
- uC: 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.
- No need for others to support software or hardware design.
- 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). Bill will probably have to do this anyway for my work.
- PCB+PNP production is actually not that hard/costly given that we'll have several PNP-d 2-layer boards soon to merge with (doing the PCB+PNP together saves costs).