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by Fat D
Sat Apr 18, 2015 11:44 am
Forum: HATs and other add-ons
Topic: How to connect a TFT screen to the pi?
Replies: 2
Views: 950

Re: How to connect a TFT screen to the pi?

A 40-pin FPC interface with those two lines cut and lots of parallel data lines on the driver board? You might be lucky and have a DPI screen, which you can get to work with the same interface used for Gert's VGA adapter. If you are lucky, the pinout is close to the screens sold by Adafruit, which m...
by Fat D
Thu Mar 05, 2015 7:00 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

Hey guys, I wrote up my experience working with DPI on my blog in the hopes that others will have an easier time than I did. A great deal of the technical information was found here so I credited you all as best as I could. If you feel left out let me know: http://blog.reasonablycorrect.com/raw-dpi...
by Fat D
Sun Mar 01, 2015 8:52 am
Forum: HATs and other add-ons
Topic: HAT Mechanical Spec
Replies: 2
Views: 1030

Re: HAT Mechanical Spec

The cutouts for the FPC cables (CSI and DSI) are an optional recommendation, you could do away with them completely if you wanted.
Source: second-to-last FAQ point on https://github.com/raspberrypi/hats
by Fat D
Sun Feb 22, 2015 9:11 am
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

The picture looks more like you mixed up the bits of the green channel. And the Logic Analyzer trace looks like you mixed HSync and VSync as well. On my display (Adafruit 40-pin one) I just ditched the two lines altogether, as DEN and DCLK were doing just fine on their own and I got a free I2C port ...
by Fat D
Tue Feb 17, 2015 6:47 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: DPI Documentation ?
Replies: 3
Views: 1245

Re: DPI Documentation ?

I already pointed you to the thread ceteras mentioned on YouTube. Currently, that is the best DPI documentation we have. But to summarize a bit: How to enable the lines not used for VGA Advanced options for the DPI interface Set custom resolution | Note: It is always hdmi_cvt, even on DPI/VGA. My su...
by Fat D
Tue Feb 10, 2015 10:39 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

CVT only specifies a handful of resolutions, and 50 Hz is the slowest one.
My screen gets by just fine in terms of wrapping without forcing a certain framebuffer resolution. I did use console-setup for a smaller font, though.
by Fat D
Fri Feb 06, 2015 11:17 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

Actually, most standard probes expect 1 Megaohm at the scope input.
by Fat D
Fri Feb 06, 2015 10:57 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

The resolution is small already. We are talking about a DPI LCD that should have a dot clock in the 7-8 MHz range based on its resolution and refresh rate. The 30 MHz clock is a symptom of the problem at hand, it should not be the cause.
by Fat D
Fri Feb 06, 2015 10:52 pm
Forum: Advanced users
Topic: Overclocking success over 1GHz?
Replies: 39
Views: 20691

Re: Overclocking success over 1GHz?

Zanith wrote:You was saying???? If you overvolt something with no cooling it would burn out (depending on voltage+current) seriously where do you get the idea that heat is good for overclocking?
But until that happens, it will manage one heck of an overclock.
by Fat D
Fri Feb 06, 2015 10:29 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

Only the Pi? As in "nothing connected at all"? You are probing ID_SD, right? With nothing connected, and it still gives off weird traces? Try changing the pin mux to I2C and tossing something out there. It should happen on bootup as the Pi probes for an extension EEPROM, set your DSO to single-shot ...
by Fat D
Thu Feb 05, 2015 9:23 pm
Forum: General discussion
Topic: pi 2 what software changes to get fsf approval?
Replies: 25
Views: 3994

Re: pi 2 what software changes to get fsf approval?

I guess the FSF would never bless as PC and it's BIOS as totally Free software no matter if the OS booted is itself all Free according to their criteria. Quite rightly so. I read once that rms used a special niche Netbook which was distinguished by having all-free firmwares. http://richard.stallman...
by Fat D
Thu Feb 05, 2015 6:54 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

That trace looks awful. Again, I wish I knew what my working trace looked like. I see nothing wrong with config and pin mux. One more idea: What kind and length of cables are there between the Pi and the screen. I am running lots of 10 cm jumper wires to a breadboard to a breakout to a 30 cm FPC ext...
by Fat D
Wed Feb 04, 2015 8:05 pm
Forum: General discussion
Topic: PoE
Replies: 16
Views: 3660

Re: PoE

There are multiple ways to realize POE. All use comparatively high voltages for microelectronics. Additional regulators would be required. Price would go up significantly.
by Fat D
Wed Feb 04, 2015 7:50 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

I am most interested in the first two or four GPIOs, because they are where the magic happens. The rest just colors things. A sinusoidal output on a Pi GPIO seems strange. Either you have way too much reactance on the bus, something resonant is connected there or there is a high impedance somewhere ...
by Fat D
Sun Feb 01, 2015 10:14 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Serial port flow control - need CTS
Replies: 10
Views: 2753

Re: Serial port flow control - need CTS

This topic went on back in 2012. These days, almost all Pi boards are either Rev2 or Plus, both of which break out CTS. And the initial project probably found a solution already or was given up.
by Fat D
Sun Feb 01, 2015 12:22 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Options for switching between multiple CSI-2 (MIPI) interfcs
Replies: 5
Views: 1750

Re: Options for switching between multiple CSI-2 (MIPI) inte

You are talking about a signal in the GHz frequency range. Adding a switch to it without proper RF design will degrade the signal significantly; you can be lucky if the circuit you are designing even works a little. Using two cameras at once is impractical without a compute module and a suitable IO ...
by Fat D
Fri Jan 30, 2015 11:20 pm
Forum: Advanced users
Topic: No /proc/device-tree on self-compiled kernel
Replies: 6
Views: 4509

Re: No /proc/device-tree on self-compiled kernel

I use this overlay for the Adafruit pitft: https://github.com/notro/fbtft/blob/master/dts/overlays/rpi/pitft-overlay.dts Thanks, that was just what I consulted to get the IRQ working. From a device tree perspective, the type of bus does not matter if the driver is the same, and the chip used by PiT...
by Fat D
Fri Jan 30, 2015 11:02 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

Do you have gpio_list installed? https://github.com/rewolff/bw_rpi_tools/tree/master/gpio If so, does it report ALT2 for the first 27 GPIOs when you execute it? How clear is the 31 MHz trace and what levels does it have? A photo might be nice if you can provide one. Also, the complete config.txt tha...
by Fat D
Fri Jan 30, 2015 2:35 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

@Gert, The RGB signals for the LCD are active high and sampled on the falling edge of the D_CLK. I have checked this with a CRO (do you still use this word or oscilloscope is the way to go?) and it appears to be OK. I was thinking of a D_CLK sync issue as the D_CLK seems faster than what the LCD ca...
by Fat D
Thu Jan 29, 2015 12:38 pm
Forum: Advanced users
Topic: No /proc/device-tree on self-compiled kernel
Replies: 6
Views: 4509

Re: No /proc/device-tree on self-compiled kernel

Copied linux/arch/arm/boot/zImage (and linux/arch/arm/boot/Image in a separate attempt) to /boot/kernel.img There appears to be an extra step in the middle that isn't necessarily obvious without careful reading of the device-tree documentation (it is easy to miss) https://github.com/raspberrypi/doc...
by Fat D
Thu Jan 29, 2015 9:52 am
Forum: Advanced users
Topic: No /proc/device-tree on self-compiled kernel
Replies: 6
Views: 4509

No /proc/device-tree on self-compiled kernel

I am running into a little trouble with the 3.18 kernel. When I install it via rpi-update, I get a nice working version with a /proc/device-tree folder structure. All fine so far. However, the version I want device tree support in the first place is that I have an STMPE610 breakout board from Adafru...
by Fat D
Sat Jan 24, 2015 8:54 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

I am still using a SD Card with RISC OS (I only have a 2GB micro SD available) but I would _assume_ that it makes no difference as the DPI is control and configured with the Bootloader.bin / Start.elf and not the Kernal.img. This may very well matter, I would recommend testing it. I could imagine t...
by Fat D
Sat Jan 17, 2015 10:32 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

Just for reference, these are my files with which I could get an Adafruit 5" DPI screen working: config.txt: enable_dpi_lcd=1 dpi_output_format=458759 hdmi_cvt=800 480 60 6 dpi_group=2 dpi_mode=87 #dpi_mode=4 #dpi_mode=9 #dpi_group=1 #dpi_mode=3 display_default_lcd=1 All below the stock Raspbian stu...
by Fat D
Sat Jan 17, 2015 7:50 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

I do not see anything that would go into the way of it. I also do not know what happens with multiple hdmi_cvt lines. I only know that the Pi refuses to boot with DPI mode DMT_87 and no hdmi_cvt.
by Fat D
Sat Jan 17, 2015 7:24 pm
Forum: HATs and other add-ons
Topic: Gert's VGA add-on for the B+
Replies: 240
Views: 118221

Re: Gert's VGA add-on for the B+

EDIT: Given the P_CLK and DE are with "no_termination" possibly I either need to externally terminate (with 100K pull up / down) or re-compile the DTS to set a termination type. This might explain the straight signals here. Question: If a GPIO is set to "no_termination" is the output structure a "s...

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