Allwinner A13 Android Tablet Usb Driver Download
Lutero Chaloux
I recently acquired an Allwinner A13 unbranded tablet in order to port Replicant to it: this platform is well supported by free software (the Linux kenrel and the u-boot bootloader) and there is an active community of developers working on free software for the Allwinner A1x platforms: linux-sunxi.
The tablet I ended up with contains an Elan EKTF2000 touchscreen, but I couldn't find any touchscreen driver for it in the linux-sunxi kernel tree: the source code was just not released, even though it's marked as being GPL-licensed. Moreover, since the tablet is unbranded, there was no one I could contact to request source code. So I asked around, and it turned out that nobody knew about source code that would have been released for that touchscreen. However, the tablet came with Android preinstalled and there was an ektf2k.ko module.
Allwinner A13 Android Tablet Usb Driver Download
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After some research, I finally found a driver for elan ktf2000 touchscreens written by HTC. It seemed to match mine (both use I2C) and preliminary tests revealed that the same protocol (on top of I2C) was used by my touchscreen. However, it was not quite enough to write an usable implementation for my device: as a matter of fact, the returned coordinates from my touchscreen did not match the screen size: it reported values up to 896x576 while the screen size is 800x640. So the whole issue was about figuring out these values (896 and 576) at run time in order to scale down to the actual screen size.
I quickly understood how the touchscreen protocol works by reading the HTC driver, and it turned out that requests were arrays of 4 bytes, with the first one set to 0x53 (indicating a request) and the second one set to a particular command (indicating what we request). Now considering that requests are usually static tables that are defined in code (that's the way it's done in the HTC driver), declared at the beginning of the function, I knew that the static array of 4 bytes corresponding to the request for the size I needed to find out was held somewhere in the ektf2k.ko module.
Looks very much like static arrays of data with the first byte set to 0x53! So I tried issuing requests with the commands 0x00, 0x60, 0x63 and 0xf0 and received the height with 0x60 and the width with 0x63! It was not in the most obvious format but 576 is 0x240 and 896 is 0x380, so it was easy to see that the responses were containing these values.
In the end, I completed my implementation, and I now have a fully working touchscreen (with up to 5 contact points) with the free software kernel!
The patch is: input: Elan KTF2K touchscreen driver with CTP bindings
Most of what I could find focused on A10 chipsets, but A13 is close enough that it might work (of course, you'll have to find A13 specific ROMs). The second link also shows how to manually install drivers. Since you didn't specify your exact model, you may have to modify the directions somewhat to work with your device.
The easiest solution, of course, is to get access to a Windows box. A year ago, Linux support wasn't so good, so I had to borrow someone's computer for a bit to flash my Allwinner A13 tablet. Even more restrictive is the ability to generate your own ROM images. I couldn't find anything that would work on Linux, so I was stuck using Windows to upgrade my tablet* to Android 4.1.
Just like my microcontroller article, the parts I picked range from the well-worn horses that have pulled along products for the better part of this decade, to fresh-faced ICs with intriguing capabilities that you can keep up your sleeve.
Network security is about limiting software vulnerabilities and creating a trusted execution environment (TEE) where cryptographic operations can safely take place. The classic example is using client certificates to authenticate our client device to a server. If we perform the cryptographic hashing operation in a secure environment, even an attacker who has gained total control over our normal execution environment would be unable to read our private key.
Processor vendors vigorously encourage reference design modification and reuse for customer designs. I think most professional engineers are most concerned with getting Rev A hardware that boots up than playing around with optimization, so many custom Linux boards I see are spitting images of off-the-shelf EVKs.
The standard 0.8mm-pitch BGAs that mostly make up this review have a coarse-enough pitch to allow a single trace to pass between two adjacent balls, as well as allowing a via to be placed in the middle of a 4-ball grid with enough room between adjacent vias to allow a track to go between them. This is illustrated in the image above on the left: notice that the inner-most signals on the blue (bottom) layer escape the BGA package by traveling between the vias used to escape the outer-most signals on the blue layer.
While many entry-level parts can be powered by a few discrete LDOs or DC/DC converters, some parts have stringent power-sequencing requirements. Also, to minimize power consumption, many parts recommend using dynamic voltage scaling, where the core voltage is automatically lowered when the CPU idles and lowers its clock frequency.
Back when parallel-interfaced flash memory was the only game in town, there was no need for boot ROMs: unlike SPI or MMC, these devices have address and data pins, so they are easily memory-mapped; indeed, older processors would simply start executing code straight out of parallel flash on reset.
Consequently, I recommend users skip over all the newfangled tech until it matures a bit more, and instead just spin up an old-school VMWare virtual machine and install Linux on it. In VMWare you can pass through your MicroSD card reader, debug probe, and even the device itself (which usually has a USB bootloader).
The old way of doing this was manually adding C structs to a platform_data C file for the board, but the modern way is with a Device Tree, which is a configuration file that describes every piece of hardware on the board in a weird quasi-C/JSONish syntax. Each logical piece of hardware is represented as a node that is nested under its parent bus/device; its node is adorned with any configuration parameters needed by the driver.
Rather than compiling all of these separately, BusyBox collects small, light-weight versions of these programs (plus hundreds more) into a single source tree that we can compile and link into a single binary executable. We then create symbolic links to BusyBox named after all these separate tools, then when we call them on the command line to start up, BusyBox determines how it was invoked and runs the appropriate command. Genius!
Even more importantly, these build systems contain default configurations for the vendor- and community-developed dev boards that we use to test out these CPUs and base our hardware from. These default configurations are a real life-saver.
Yes, on their own, both U-Boot and Linux have defconfigs that do the heavy lifting: For example, by using a U-Boot defconfig, someone has already done the work for you in configuring U-Boot to initialize a specific boot media and boot off it (including setting up the SPL code, activating the activating the appropriate peripherals, and writing a reasonable U-Boot environment and boot script).
The Microchip, NXP, ST, and TI parts are what I would consider general-purpose MPUs: designed to drop into a wide variety of industrial and consumer connectivity, control, and graphical applications. They have 10/100 ethernet MACs (obviously requiring external PHYs to use), a parallel RGB LCD interface, a parallel camera sensor interface, two SDIO interfaces (typically one used for storage and the other for WiFi), and up to a dozen each of UARTs, SPI, I2C, and I2S interfaces. They often have extensive timers and a dozen or so ADC channels. These parts are also packaged in large BGAs that ball-out 100 or more I/O pins that enable you to build larger, more complicated systems.
The Nuvoton NUC980 is a new 300 MHz ARM9-based SIP with 64 or 128 MB of SDRAM memory built-in. The entry-level chip in this family is $4.80 in quantities of 100, making it one of the cheapest SIPs available. Plus, Nuvoton does 90% discounts on the first five pieces you buy when purchased through TechDesign, so you can get a set of chips for your prototype for a couple of bucks.
Speaking of that 64-pin chip, I wanted to try out that version for myself, just for the sake of novelty (and to see how the low-pin-count limitations affected things). Nuvoton provides excellent hardware documentation for the NUC980 series, including schematics for their reference designs, as well as a NUC980 Series Hardware Design Guide that contains both guidelines and snippets to help you out.
There may or may not be official dev boards from Allwinner, but most people use the $7.90 Lichee Pi Nano as a reference design. This is set up to boot from SPI NOR flash and directly attach to a TFT via the standard 40-pin FPC pinouts used by low-cost parallel RGB LCDs.
The chip needs a 3.3V, 2.5V and 1.1V supply. I used linear regulators to simplify the BOM, and ended up using a dual-output regulator for the 3.3V and 2.5V rails. 15 BOM lines total (including the MicroSD card breakout).
All told, the SAM9X60 has 13 UARTs, 6 SPI, 13 I2C, plus I2s, parallel camera and LCD interfaces. It also features three proper high-speed USB ports (the only chip in this round-up that had that feature). Unlike the F1C100s and NUC980, this part has Secure Boot capability, complete with secure OTP key storage, tamper pins, and a true random number generator (TRNG). Like the NUC980, it also has a crypto accelerator. It does not have a trusted execution environment, though, which only exists in Cortex-A offerings.
Microchip selectively-depopulated the chip in such a way that you can escape almost all I/O signals on the top layer. There are also large voids in the interior area which gives ample room for capacitor placement without worrying about bumping into vias. I had a student begging me to let him lay out a BGA-based embedded Linux board, and this processor provided a gentle introduction.
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