Where Can I Buy A Serial Cable?

[Klepto]

I know you used to be able to buy them, but that site is offline now. I really really want one, but I don't personally possess the skills or tools to build one. Is there anywhere else I can buy a serial cable for my GP2X?

 

[Squidge]

art103 is selling them with his usb host cables. It's basically a lead from the gp2x with both usb host and serial -> http://www.artaylor.co.uk/~richard/gp2x/

If you only want it for program debugging however, why not try gfoots usb method?

 

[Klepto]

Thanks Squidge, that's just what I was looking for.

If you only want it for program debugging however, why not try gfoots usb method?

​

I'm using the USB serial stuff ATM, but at some point I will be wanting to run/debug stuff in raw mode (no OS), and I imagine writing a serial driver is gonna be a lot easier than the equivalent USB method.

 

[Squidge]

Ah, well in that case, if your programs runs from uboot or later in the sequence, it's a simple matter of writing to a single register to output bytes via the serial lead. uboot sets it up at 115200 8/n/1 for you. To do it properly, you need two registers (one which says when the byte has actually been sent), but it's still a lot less work than usb.

 

[Klepto]

Using uboot is the way I want to go. It's still early days, but basically it's related to this post. At some point I'll probably start another thread related to this, but right now it's just ideas.

 

[Squidge]

Well in that case, I'd download Rob Brown's SDK2x, which works really nice in uboot as that's what it was designed for.

Unfortunately, there are currently only two ways of running non-OS code on a retail system:

1) [Safest, Slowest] Use a trampoline. Rob has one in his SDK. This is basically a Linux application that kills the OS by resetting the processor, and then takes over after initialisation. The downside to this is the 20+ seconds to wait for the OS to bootup every time you want to try your code.

2) [More dangerous, but faster] Upload code via serial lead and let uboot execute it for you. Much quicker turn around, and no sd card required. Downside being that on a retail system, you have trash the linux kernel at least once (ie. flash a known bad kernel to force a crc failure), otherwise it'll pass control to the kernel and you don't get a look in. Once you've done it once however, you can add a small delay before it looks for the kernel - so you can put the good kernel back after the patch is done.

Oh, and from your post you say the ARM doesn't have a stack. Well, it doesn't have a hardware stack, sure, but then again it doesn't need one. Just reserve a small amount of ram somewhere, and you can use any register you want as a stack pointer. R13 is the preferred register however. Look at the LDM/STM instructions.

 

[Klepto]

Well in that case, I'd download Rob Brown's SDK2x, which works really nice in uboot as that's what it was designed for.

Unfortunately, there are currently only two ways of running non-OS code on a retail system:

Cool, I'll have to have a look. I'm not at that stage yet tho... right now I'm still learning ARM assembly and working an a Forth compiler that's hosted under Linux. The idea is to then port the assembler/disassembler here to the hosted forth and use it to write a bootable image of a native version of the same Forth.

Option 1 is fine for me, but if this thing was ever to produce mainstream s/w then something like option 2 would really be a must IMO. I have yet to read up on uboot and the gp2x boot sequence though.

Oh, and from your post you say the ARM doesn't have a stack. Well, it doesn't have a hardware stack, sure, but then again it doesn't need one. Just reserve a small amount of ram somewhere, and you can use any register you want as a stack pointer. R13 is the preferred register however. Look at the LDM/STM instructions.

​

Yeah, I think I made that post a couple of hours after starting to read up on it. One of the first things I read said (in big scary letters): "THE ARM HAS NO STACK!". I have since learned that this isn't a problem, Forth uses 2 stacks so the ARM architecture is probably better than a machine with a single hardware stack.

 

[nubie]

I go to axshop.com and get the Samsung e810 serial data cable,

see my thread about the serial cable, I will be making a set of instructions on how to build it into GP2X compatible.

The cable has a built in serial line-level chip in a PCB under the shell on the PC side.

Only 4 cables to connect, simpler than a mod chip, I can also build one if you really need it, I have another one coming, I sold my last one on ebay with my GP2X.

they are $5.24 from axshop.com, really really cheap.

I could probably make you one for $10-$15 if you needed it.

 

[slygamer]

Well in that case, I'd download Rob Brown's SDK2x, which works really nice in uboot as that's what it was designed for.

​

SDK2x is available? When did this happen? There is no information on his website. Where do we download it from?

 

[Squidge]

Its available (and already has been available) to people who want to test it via asking him in the dev channel on irc. There's no public release as of yet as its still not complete.

 

[slygamer]

Its available (and already has been available) to people who want to test it via asking him in the dev channel on irc. There's no public release as of yet as its still not complete.

​

I tried, but no-one responded. Then again, no-one was talking at all. Lots of people, but nobody home.

I guess I'll wait for a public release.

 

[Squidge]

I don't know what time zone your in, but in the UK, Rob seems to come online between 7pm - 8pm, and falls asleep sometime after 10am.