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1082 discussions

goodbye LM13700, hello CM108AH
by luke.leighton 29 Oct '13

29 Oct '13

it is with much sadness and regret that for parts in the flying squirrel i say goodbye to the LM13700M, a part with a huge and rich history, having seen its first emergence into the world around 1967 even predating the moon landing. the reason is simple: the bias for the diodes is 3x 0.7 volts and on rails of +/-2.5V it's simply not enough. i'm seeing silence at low volumes... and then huge clipping. i simply don't have time to resolve this. instead unless there's a good reason (e.g. conexant responds to enquiries) i'm going with the CM108AH and keeping the TDA2822 as a speaker amplifier. the reason for choosing the CM108AH: no good reason other than the datasheet contains an example schematic and there were no NDAs required to get hold of that datasheet. l.

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[flying squirrel] schematics review needed
by luke.leighton 29 Oct '13

29 Oct '13

hi folks i'm onto the 3rd revision of the flying squirrel, i need help: a systematic review of the schematic pages, to make sure i haven't missed anything. the schematic is partly copied from other drawings as well as application notes. the CM108AH is to be replaced with a Conexant USB-Audio IC. the pdf's here: http://hands.com/~lkcl/eoma/tablet2.pdf - any comments gratefully received. timescales are short but a careful review is essential. thank you everyone. l.

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car "infotainment" doesn't upgrade....
by luke.leighton 24 Oct '13

24 Oct '13

http://tech.slashdot.org/story/13/10/22/2211209/automakers-struggle-with-pa… funny that....

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[flying squirrel] revision 3 started
by luke.leighton 24 Oct '13

24 Oct '13

http://rhombus-tech.net/community_ideas/kde_tablet/news/revision_3_starts/ well... i've been quiet for the past few days because i've been incredibly busy. the experiments with the STM32F103 for use as a camera _would_ i think eventually have been fine... except that the speed simply wasn't up to scratch. so instead an extremely rapid bit of evaluation took place (thanks to a friend at atmel) and the SAM4S QFN64 was picked. the past two evenings have been spent doing a near-complete re-layout of the PCB. by shrinking the component sizes (0402) it's been possible to make just enough space to optionally fit a SATA, Ethernet, 4-pin header for USB and a 12-pin FPC as an expansion port. WIFI stacks on top via a 2nd 4-pin USB header with 3.3v power. there's going to be a bit of connector shuffling before this goes out, but it's basically doable. so, in effect, this PCB is one step away from being the Monster Engineering Board. it's also only 12cm x 10cm (under 5in x 4in) which is nice. l.

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One other thing -- emulation question...
by Christopher Havel 23 Oct '13

23 Oct '13

One more idea that just popped up (I promise I won't spam the list too much with this kind of junk). How much of a performance penalty/loss would be incurred by "pulling a Transmeta" -- by which I mean emulating x86 hardware with, in this case, ARM...? Say, convincing an A20 to emulate something like a P3 CPU? The idea comes from the Transmeta Crusoe CPU -- which is NOT x86 at all! It's something I'm really unfamiliar with called VLIW, and it has what amounts to a software emulation layer between it and the rest of the system, so that it can run x86 code. Of course that incurs an INSANE amount of overhead, because the CPU is basically doing its job twice -- translating the instructions and then executing them. It's a remarkable kludge if you ask me, but it works.

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Just a thought...
by Christopher Havel 23 Oct '13

23 Oct '13

It occurred to me, just now, that if the MEB (or any other EOMA-68 carrier board) is put in a housing with built-in guides for the CPU Card, then we don't necessarily need a proper PCMCIA slot -- just a 2x34 right-angle pin header with 1.27mm spacing. Have the bezel of the CPU card stick out just a touch from the housing, so that someone can get their fingernail (or a small slot screwdriver) under it and pry just enough so that they can yank it out. Seems to me that it'd be a cheaper option as well, because of the wonders of injection-molded plastic... even making the housing out of something fairly sturdy, say 2mm ABS, surely wouldn't cost too terribly much... plus, it's potentially possible to 3d print such a thing, which would make this stuff even more accessible to the (far richer than me) hobbyist. (Of course it'd also be possible to 'jerry-rig' it with scrap materials and lots of fussing.) I'd love to see a housing like that, with a small carrier board (perhaps a VGA-enabled version of the MEB?) and a VESA 75mm mounting option. It would enjoy a permanent placement on the back of my spare LCD for sure. (The carrier board would definitely have to support VGA through some means, though, to work with that screen.)

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lkcl: you jammy toe rag!
by joem 22 Oct '13

22 Oct '13

http://www.gplsquared.com/eoma_boot/video-2013-10-21-15-06-42.mp4

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Progress Report
by martin brook 22 Oct '13

22 Oct '13

Hi Guys, Just a quick note on my progress with EOMA and MEB EOMA Adaptation packages at http://repo.merproject.org/obs/home:/vgrade:/branches:/home:/mdfe:/hw:/sunx… Followed instructions at http://www.gplsquared.com/eoma_boot/eoma_boot.html to get eoma to boot from sdcard, please note use, http://www.gplsquared.com/eoma_boot/script.fex_2013_09_17 Mer image boots from sdcard, hdmi, serial, ethernet all working Pic of board running libhybris test_glesv2 https://twitter.com/vgrade/status/392416401790869504/photo/1 Thanks to all involved in bringing EOMA, MEB, linux-sunxi to the community. BR Martin

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stress! and working with libopencm3, stm32sprog and an STM32F103
by luke.leighton 21 Oct '13

21 Oct '13

well. there is a particular issue with stm32sprog which has massively hindered progress over the past few weeks. it's very simple: when uploading and running a program using stm32sprog, if it has interrupt service routines it is guaranteed to crash. however if you then set BOOT0 to 0 and do a RESET, the program will work absolutely fine [assuming it's coded correctly] this simple little thing has prevented progress over the past couple of weeks because it has been impossible to distinguish "code incorrectly written" from "code that crashed due to stm32sprog". dozens of examples and bits of code that _should_ have worked - DMA, ADC, DAC, Timers - will and can now all be revisited. patience, patience... ... anyway i'm currently tracking how to get timers to update from an external gpio pin, and from there to fire DMA. it _is_ possible... just.... requires a huge amount of careful reading and research just to come up with only 30 lines of code that connect all the dots together without connecting any of the thousands of other options. i think... to be absolutely honest, if i had known that the STM32F was so comprehensive / complex i would have said "sod it" and used a low-cost FPGA instead. but, hey, this is kinda hair-raisingly fun.... l.

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Allwinner A10 vs A20 power requirements
by Alexey Eromenko 20 Oct '13

20 Oct '13

Hi, I was unable to find the power requirements for A10 and A20 chips. (under near idle use and max. Performance scenarios) Do you know where that data is buried? (A20-based Cubietruck, according to documentation, can work with 0.5 amp x 5 volt = 2.5W total for the board, without SATA. ) What about Raspberry Pi's Broadcom chip? What it's power requirements? Alexey

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