Noob question about TI Stellaris Launchpad EK-LM4F120XL - Page 1
Forum section: electronics / general

author: BravoV
author_rank: Super Contributor
timestamp: November 10, 2012, 06:21:04 am
content: I realized upon unboxing this board, it has two identical LX4F120H ARM mcus, so the left one's purpose is solely for ICDI function only ?Just curious why need such powerful auxiliary chip for just the in circuit debug feature ? Again, this is a noob question here.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: November 10, 2012, 06:53:20 am
content: First I will make the assumption that this processor (the target processor) is an ARM cortex m4 that is using the standard ARM JTAG/SWD circuitry and not some proprietary interface (I haven't read the data sheet). It does not require anything like another cortex m4 to run the JTAG, all you need is a USB to serial like FTDI 2232, Dangerous prototype's Bus Blaster for example. Although I am almost certain the FTDI chip also has a common core processor (could be an 8051 derivative - don't quote me) onboard. All of the semi manufactures use one of their own chips to provide jtag for their development boards . NXP uses an LPC1343 in their LPCExpresso series, ST uses a STM32F103 in their ST-Link2 STM32 Discovery boards ect. Why wouldn't they use their own products?

author: Bored@Work
author_rank: Super Contributor
timestamp: November 10, 2012, 07:23:01 am
content: Of course, when a company does a demo board they want to use their own chips on it for as much stuff as possible. It is a prestige thing to not have competitor products on a demo board.Why they used the same chip? Maybe to reduce production cost. It is one feeder less for the pick and place machine. It makes logistics, procuring and storing the different parts for production a bit simpler.The hardware team, when designing the board, only has to deal with one kind of MCU. One datasheet less to study. The same basic connection for things like power and clock. Same footprint. Same for the software team doing the firmware and demo software. It only has to deal with one kind of MCU.We can also safely assume that TI's internal cost for the chip is fare less than it's official list price. In the end using the totally oversized MCU was maybe even cheaper than using something else.

author: mrflibble
author_rank: Super Contributor
timestamp: November 10, 2012, 02:09:32 pm
content: Quote from: BravoV on November 10, 2012, 06:21:04 amReflected sound as of underground spirits.

author: andersm
author_rank: Super Contributor
timestamp: November 10, 2012, 04:02:03 pm
content: JTAG and SWD are not very well suited to run over USB. By putting more smarts into the adapter, you can use better protocols over the (relatively) high latency bus, and translate into JTAG or SWD commands locally. Why TI chose an LX4F120H in particular is anyone's guess. Could have been a case of dogfooding on part of the Launchpad team, or making a point of the chips being so cheap you can put two of them on a single board or whatever.

author: BravoV
author_rank: Super Contributor
timestamp: November 10, 2012, 05:20:15 pm
content: Thanks for the responses and insights, yeah, I've thought about dogfooding or the prestige too.But I think the most reasonable is this Arm M4F is still new for TI, and putting both will be the best situation for their internal team and also "us" the early adopters to iron out the bugs.Cause after digging deeper at TI web site, also into the datasheet + the so called errata documentation, lo and behold, TI's Arm Cortex M4F families basically is not even at the production stage yet.Well, personally I can't complain too much since the price was dirt cheap at $4.99 during the promotional period, no wonder.I guess the new batch with the $13.99 price tag doesn't have the e"X"perimental chip and much-much less erratas and hopefully with workarounds for fatal ones.Just look what I've discovered, the chip shot + notes should be sufficiently explain what I mean.Edit : Btw, this board's batch code is on week 41, go figure.

author: BravoV
author_rank: Super Contributor
timestamp: November 10, 2012, 05:37:06 pm
content: Quote from: mrflibble on November 10, 2012, 02:09:32 pmHuh ?

author: rolycat
author_rank: Super Contributor
timestamp: November 10, 2012, 06:29:11 pm
content: Quote from: BravoV on November 10, 2012, 05:37:06 pmEcho-nomics.See The Colour of Magic by Terry Pratchett for further enlightenment.

author: TheDirty
author_rank: Frequent Contributor
timestamp: November 10, 2012, 10:06:55 pm
content: Quote from: chickenHeadKnob on November 10, 2012, 06:53:20 amFT2232 JTAG is relatively slow and FT2232 adapted to SWD is even slower.It is kinda annoying that we have all of these different proprietary standards. LPC wont even release the documentation on LPC-Link. At least Crossworks supports both ST-Link and ICDI.Quote from: BravoV on November 10, 2012, 05:20:15 pm41st week of the year, not 41st week of production. That wasn't that long ago. They are putting them on boards pretty quickly.

author: rsjsouza
author_rank: Super Contributor
timestamp: November 10, 2012, 11:45:15 pm
content: Usually the parts that are eXperimental did not go through the full characterization process (mostly electrical specs) due to the length this takes even after perfectly functioning parts are already available internally. Therefore the idea is to put parts out so people interested in them can start software development while the complete characterized parts for production become available.This in general has little to do with the silicon Rev and its functional bugs usually listed in an errata - these take a lot longer to fix.

author: BravoV
author_rank: Super Contributor
timestamp: November 11, 2012, 06:24:19 am
content: Rafael, thanks, so this is common practice, especially for new product, guess I have to live with it.For me as a beginner, pretty sure those unsolveable erratas should not be a deal breaker for me.

author: westfw
author_rank: Super Contributor
timestamp: November 11, 2012, 07:43:08 am
content: Note that the stellaris launchpad does better than the MSP430 launchpad, which used THREE TI chips to implement the debugger interface.

author: vis1-0n
author_rank: Contributor
timestamp: November 11, 2012, 10:11:16 am
content: The STM32F0 discovery had the superior ST32MF103 to target the STM32F100. The LPCXpresso shipped with the LPC3154 which is a wet dream compared to the LPC1114 (or LPC1769) target. The LPC3154 is a so much more desirable chip, wish they had broke that out and allowed firmware updating.BTW anyone experiencing any serial comms issues with the Launchpads virtual serial port? I have not been able to get Hyperterminal/ Putty to work, although Putty works okay on fresh boot on the VM Host machine and fails (VM and host) when I attempt using the VM. The programmer/debugger has no issues in VM.

author: BravoV
author_rank: Super Contributor
timestamp: November 11, 2012, 11:55:07 am
content: Quote from: vis1-0n on November 11, 2012, 10:11:16 amNever experienced with ST's or NXP's Arm though, any comment how these two compare with TI's "especially for beginner" like me ?Quote from: vis1-0n on November 11, 2012, 10:11:16 amWeird, what host or client OS ?Don't have any problem at all, everything run smoothly and it worked straight from the 1st time I hooked it up at the VM, host OS is Win 7-x64 with XP as the VM client OS.Screen shot attached below with my browser pointing at this page, and the VM (XP) running Hyperterminal connected to the stellaris launchpad.

author: andersm
author_rank: Super Contributor
timestamp: November 11, 2012, 07:08:24 pm
content: Quote from: BravoV on November 11, 2012, 11:55:07 amThe Cortex-M's are pretty much interchangeable. They all use the same core, and all manufacturers have peripherals that offer more or less the same functionality. There's differences in the implementation details, but it doesn't make one make inherently more difficult to use than the others. I haven't really used the manufacturer's software libraries, but NXP's seemed the most rudimentary and TI's the most developed.The LPC3154 that was mentioned is a low-end applications processor aimed at embedded Linux and the likes, and very different from the microcontroller lines.

author: andersm
author_rank: Super Contributor
timestamp: November 11, 2012, 09:42:49 pm
content: Quote from: T4P on November 11, 2012, 08:56:50 pmNot really relevant to the discussion, but the PICkit 3 uses a PIC24F.

author: BravoV
author_rank: Super Contributor
timestamp: November 12, 2012, 07:50:57 am
content: Quote from: andersm on November 11, 2012, 07:08:24 pmThanks for confirming, so far my own experience at TI's tools, documentations, tutorials and also their training videos, I would say it is good enough for noob like me to start into ths arm cortex platform. No big ambition though, just aiming for 'enthusiast' grade projects in the future.

author: vis1-0n
author_rank: Contributor
timestamp: November 12, 2012, 08:07:13 pm
content: Quote from: BravoV on November 11, 2012, 11:55:07 amWinXP sp2 on VMWare, host is Win7 32 bit. What VM software are you running? VirtualBox? This is pretty annoying as after many years I finally sat down to actually learn and I can't get this working. I guess I will have to install onto the host, I rather hate doing that as I don't connect to the internet with it at all. This will also be less portable than the VM, the last time I had a failing HD it was so easy to restore a backup of my applications.

author: BravoV
author_rank: Super Contributor
timestamp: November 12, 2012, 11:48:15 pm
content: Quote from: vis1-0n on November 12, 2012, 08:07:13 pmSame here using VMWare Workstation (see the screen shot) except my host is Win 7 64bit, and also it runs fine on VMPlayer as well.No extra tweaking applied at the VM, everything run on stock setting.Edit : Just verified it again by plug&unplugging the Launchpad board, no problem at all and running well at VMPlayer ver 4.0.4 build-744019.