Working with SD cards and others

[Sceadwian]

Dirtylude, I had no idea what the OPs level of expertise was when I responded. He asked for input, I gave it. Why am I being picked on for sharing what I think are very real possibilities? Even if it's over the posters head god forbid they're exposed to something outside of their skill level =) As far as Nigel post goes I'm sorry but that's not a technicality, 0-5 volts triggering the inputs of a PCs RS232 is an accident of the PCs construction and it does violate the RS232 specification.

Ozirock, As far as doing it in ASM, yeah that's pretty much shooting yourself in the foot =) You could relatively easily access an SD card in ASM but the file system would be difficult. It is possible to do it using a known offset for the file on the SD card then you can bypass the filesystem as long as the file is exactly where the MCU expects it to be and not fragmented at all, but that requires comfort in using a hex editor on a PC to determine the exact location of the file and it can never be moved. I honestly wouldn't try it without using C unless you're just doing it for kicks.

 

[ozirock]

Thanks for the advice Sceadwian, I'll look into getting a C compiler to work. I lost patience with it the first time I tried and decided I might as well learn assembly language so when I complete the tutorials I was doing and feel happy enough with it, I'll try get the C compiler working and see how I get on from there

 

[Sceadwian]

If you're programming micro controllers some ASM is a really a good idea if not really required, because even when you program in C you're still using a lot of the same syntax as you were in ASM because the hardware and the way you code is so much different than say C code for a computer. Once you complete your tutorials play around with ASM some more until you're comfortable with how things work, C is actually easier in the long run for more complicated code, but if you can't deal with ASM for basic stuff C isn't gonna be any easier, even if it CAN be more powerful.

 

[ozirock]

Grand I'll try do as much as I can in ASM before I go near C. I did a module on C programming in first year which should help with the basics but it had nothing to do with micro controllers so I'll just have to give it a go and see how I get on.

 

[Nigel Goodwin]

Because Nigel, technically all PC's are supposed to require those voltage levels to be actually called RS232, the fact that a single resistor to protect the PIC and 0-5 volts from the PIC can trigger a PCs RS232 port is an accident of construction only and is technically a violation of the standard.

And why would that be any concern whatsoever? - many PC's didn't meet the RS232 standards, which (as I said) was based on antique mechanical teletypes - and has little or no relevence for almost all modern uses.

 

[Sceadwian]

I've responded to Nigel's post in a private message because it doesn't relate to this thread as serial communication was not the topic.

 

[Mr RB]

And why would that be any concern whatsoever? - many PC's didn't meet the RS232 standards, which (as I said) was based on antique mechanical teletypes - and has little or no relevence for almost all modern uses.

I'm with Nigel on this one, the whole RS232 standard was based on making long distance serial comms over poor cabling reliable. For a 4 foot wire to plug a PIC into a PC its quite a ridiculous amount of overkill.

But of course it became a standard so we are condemned to putting up with its silly overkill even though we are not communicating down 500 yards of crappy old coax through the middle of a factory.