I tend to use RS232 for debug but given the choice between I2C and SPI for peripherals I generally prefer I2C as you dont have to use seperate slave select lines. I also find that I2C is more standardised between devices whereas I have run into incompatibilities with SPI.
@garysxt: To reduce the firmware complexity. Instead of having to meld in the MAL USB driver firmware, I only have to key relatively simple RS-232 TX/RX routines that get translated to USB and back by the FTDI part.
@FredEady Thanks. Our application communicates with a cellular modem just using the PIC's UART--don't even need to use RS232 level translation. I think the main issue is getting the modem into a mode to stream the hex data to a buffer, then programming the FLASH and dealing with any communication errors. I'm here as a first step on my journey to understanding and implementing this.
@JeffM the interface IS strange. You get used to it after a while and almost anything can be done from the keyboard. And you can setup whatever keyboard shortcuts you want in it's ini file. And the newest version stores the schematics and boards as xml files you can edit outside eagle. I've used that to easily globally change things like line sizes.
@aefelgate: I have seen this done. It all depends on the I/O capabilities of your cell modem. I would imagine you would have to interface to the cell modem's serial interface, which could be RS-232 or Ethernet. Depends on the modem. There were some participants discussing that yesterday on this blog I think...
@gberman: That's assuming the embedded device has an Ethernet port. I can see your idea of sending code to be loaded onto the remote microSD card via internet/ethernet as a way to avoid shipping delays and costs.
@JeffM actually there is a free version of EAGLE, limited to 1 schematic sheet, 2 layers, and 4" square max pcb. They also have a "for home use only" version for around $100 that removes all those limitations.
@FredEady We would like to take advantage of our existing cellular connection to our device to remotely update the firmware. Have you experience with this? Or, can you point us to some additional info?
@miket: Instead of showing up at a customer location to "reprogram" the micro for a version update or bug fix, you simply put the new code on a microSD card and drop it in the mail. They get the microSD card, plug it in, push a button and WHAMO the version is upgraded or the bug is squashed. If you're a Florida company and the customer is in Oregon, it's either an airplane ride or a UPS/USPS/FEDEX package.
@BrokenRotor: I like ExpressPCB. You get CAD and schematic capture free. Plus, you can order Gerber files of your projects from ExpressPCB. I use the Gerbers to have stencils made for large production projects.
I've tried those services in the past, like them, but felt there was too much of a premium involved. I was thinking about using Kicad, though I don't know much about it, except it's free and open-source. I've been a bit suspect of RS Design Spark, though maybe that's unwarrented.
@MazianLab: A bit of trivia.. National Semiconductor helped name my company. They mispelled my last name ED instead of EADY in their database. So, I was Eady Technical Publications until that little miscue. Lots of suppliers made that same mistake. So, I decided to make it easy for everyone and dropped Eady in the company name to become EDTP.
@Kentj I have to have it cranked up 450/Toast on the Bake setting. Only takes about 2 minutes to reflow. Don't use the wax markers; I just watch the board through the glass until the paste turns to quicksilver.
@Jeff M: I use Express PCB for schematic capture and board layout but you're limited to four layers. I think you get more layers with PCB123 but it's harder to create your parts library. Both are free. PCB123 you're restricted to only one board fab house though.
This could come in handy to build an interface for legacy PLC applications that only support RS232 especially since the manufacturers can't seem to built a reliable interface. Will need to look at this more in detail later.
The FT232RL part is very easy to use, we use it a lot (we'll use it as as debug port rather than put in RS232 interface). Typically, we opto isolate it from the microprocessor because of the current limitation of the USB port.
Boot loader interfacing dependes on what's avaiable. If you already have a communications mechanism (RS-232/RS485/CAN/Ethernet/RF) use it to avoid additional costs unless the driver for it makes the boot loader too big.
In general, the cost and board area for an SD card is actually above our threshold. 3.3V Serial with a 3 pin header is about what we can tolerate (may even drop the 3 pin header and only use test points for connectivity). SWD is typically only used for factory programming and many devices are reprogrammed or tossed if they don't work.
Did any one see link to the source code for this project ? When I go to the EDTP site (www.edtp.com) all I see is a shopping cart page for buying EDTP AirPlane card . What link navigates to schematics or source code?
It used to be that a simple RS-232 bootloader was the cheapest way to go. These days, the FTDI parts are just as cheap or cheaper than the RS-232 drivers. To really get down and dirty, eliminate the RS-232 IC and replace it with a couple of transistors and resistors. The LCD would also have to go.
@Kentj - John Fluke, Bill & Dave and Howard were a breed that appreciated customers and employees and used that to drive their decisions. Dahaner just look at their acquisitions as something to fuel their next acquisition (lean out the costs in an organization to get profits).
John Fluke wanted to support equipment for seven years after obsolesence. When Danaher took over they got rid of support parts so they couldn't be maintained. I intercepted the parts from the dumpster and brought them in whenever needed as long as I worked there.
@uWave Hunter - Leviton Manufacturing (Melville NY) started out making gas mantles for indoor lamps and when Edison came along tehy recognized the shift in market and started pursuing electrical. Flat prong plug and pull chain light sockets were Leviton's inventions.
There is also a branch of BBQ that comes out of South Carolina (I believe) that uses a vinigar &/or mustard based (not tomatoe based) sauce that doesn't have as much sugar. that might also be an option.
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