• [T] Inbuilt A4 Document Scanner

    kelvinA05/23/2023 at 22:01 0 comments

    Since I'm unbound by the generic requirements of "the masses" and have complete idea freedom until "the rubber hits the road", as they say, I was wondering about any additional features I could install into Leti. The requirement was that:

    1. it had to actually be useful, and
    2. it needed to fit inside the space available, as well as not being possible to do in a smaller form factor by using a phone.

    Those 2 points eliminated the first round of ideas, such as a high FPS camera, 360 degree camera or infared camera. The first point stopped me from considering a pico projector, which happens have existed in quite a handful of phones actually:

    I thought there was only 1 .

    Anyway, I then thought back to when someone made a reddit post in r/framework about "dumb" expansion bays, where I suggested an A4 doc scanner. This is the humble pocket scanner I owned way back in 2018 or 2017:

    It broke almost a year after I bought it, but it allowed me to get nice images of flat surfaces, however due to the design flaw that I'd like to address, it wasn't all that great at scanning books. Essentially, I need to get the scanner as close to the longest edge so that I can scan right up to the middle of the book. Still, it was quite fun to use, though a bit tedious since it was a seperate device that needed to be charged and you had to use a micro SD card to transfer the files to the PC and it cost something like £80 for the WiFi edition. With that WiFi edition, you'd actually need to connect to the network that the handheld scanner generated, so it's not like the workflow was all that much smaller.

    The idea would be to try and use the sensors I've found for the #SecSavr Suspense [gd0105], which is MUCH cheaper than the £50 I spent on that handheld scanner.

  • [E1][R] Monitor Splitting Strategy

    kelvinA05/23/2023 at 19:12 0 comments

    I think it's time I started researching how I'm going to get the side screens to act like 2 seperate screens. The main idea is to drive 2 screens from one TB-chip, just like below:

    In the image below, I show what any device will automatically display on the top, and how I actually want it to display on the bottom:

    I'm not yet sure if I want the side screens aligned to the top or to the bottom (as shown). I think the latter looks a bit like a 3D carousel.

    So I'm thinking that my options are:

    1. Give up on 90Hz OLED and go dual 60Hz Mini-LED 6.3's, even if Leti would probably be as long as a 16" laptop is wide (360mm). 
      1. Use the extra length to fit in a 148Wh battery (up from 111Wh). I'm not planning on flying, but apparently you can take up to 160Wh inside carry-on luggage. The 100Wh limit is for suitcases.
      2. The issue with this one is that 360mm might be hard to use one-handed and it may be uncomfortable to look at one screen or the other since I'd likely have to turn my head.
    2. Find software that can configure the screens.
      1. I found "DisplayFusion", but at this time it doesn't support fullscreen windows.
    3. Try and find a USB3.0 -> HDMI that supports 1200*1080px 90Hz.
      1. This would allow Leti to drive 3 external monitors instead of 2, since both Intel and AMD have a cap of 4 monitors on the iGPU.
    4. Run each monitor directly, and just turn off the side monitors if I want to use external monitors.
      1. I'd also need a second I2C bus since the TB-chip only supports 2 different addresses.
    5. Wait. What if I flip the script entirely and do 4, but the OLED is the center screen?

    Here me out here:

    Am I really going to pick this device up to skim though 25 research papers while I run computational fluid dynamics on a CAD model most of the time? 


    Why run dual QHD panels all the time when I probably could use less-than-HD real-estate more than 50% of the time? This would be similar to a laptop + 2 desktop monitors arrangement. This solution seems to get more of the benefits and less of the drawbacks:

    • Benefits
      • Higher utilisation of the TB-chips.
      • 2 QHD sunlight readable displays instead of one.
      • No bezel in the neutral neck angle (looking straight ahead) and I can hide the bezels of the QHD monitors behind the OLED panel.
      • Excuse for an even larger battery.
      • Main screen is the right orientation by default, and is 90Hz.
      • If I had 2 screens of slightly different PPI's, I'd prefer the center one to have the lower PPI since objects would be slightly larger than the ones on the secondary screen. 
    • Drawbacks
      • Still probably 360mm long. On the bright side, that gives Leti a body ratio of 3:1.
      • The center screen is a barely-passing 75PPD resolution, and I worry that websites will have display issues with 1080px horizontal.

    This not-a-notch design likely would be better as I'd more easily fit a webcam:

    [25 May: Edit 1] I'm also thinking of virtually splitting the 6.3" panels in half. The center screen has an aspect ratio of 0.9:1 and these virtual side monitors would have a very similar aspect ratio of 0.889:1. The fullscreen bug becomes a feature in this way too.

  • [E2][R] DIY Mini-LED 1440p LCD

    kelvinA05/20/2023 at 00:26 0 comments

    So, as I mentioned in the initial research log I've edetid a few times now, the 6.3" LCD can be bought with or without a backlight.

    So, as a person of many long winded projects and projects within projects, I thought "You know... maybe it's possible to get most of the OLED benefits without the OLED drawbacks and DIY a mini-led-style local dimming zone array like the iPads."

    So, since I know about the world of LED matricies because of the T^2 Tiles, I knew that it was possible to build a 2mm pitch matrix. The 6.3" has an active area of 79 x 140mm so that's essentially 39 x 70 = 2730 dimming zones. 40 x 70 = 2800 zones would probably be better as it'll cover every milimeter of the active area. I've heard that there's 2500 diming zones in the 12.9" iPad Pro, so if Apple thinks 2.5K zones is a good amount, I'll belive them.

    Now I was wondering how I'd even get so many LEDs on a single PCB. I thought I'd just use an off the shelf P2 64 x 64px matrix as a development solution and figure it out at a later date. I also considered white 1.9mm matrix modules, but it would likely be too thick and too expensive.

    But, as it turns out, if I'm fine with 2.5mm pitch, I can get a 160 x 80mm LED matrix!

    On the surface, they all seem similar, but the achievable brightness levels vary. So far, the lowest I've seen is 1000 nits and the highest is 1800. Remember that, due to the polerisation of the LCD, I'm losing at least 50% of the brightness. 40% efficiency is probably a decent estimate.

    Thus, I'd expect to be getting 720 nits from the 1800 panel. Not quite HDR1000 but still brighter than all other screen options. Speaking of options:

    It seems that the second option is overall better since it's got a higher viewing angle, though the first one has a calculated max power of 15.36W. 14 bits per colour seems a bit excessive though... no? At least that means that there can be very granular white levels. I also wonder what "LED Display Voltage" is all about; surely they're not driving LEDs with AC power. Anyway, as you might be able to guess, the first panel is slightly cheaper, though only by £3.

    Moving on, the matrix that would actually need to be driven is 32 x 56 = 1792 local dimming zones, which is probably fine for a DIY run. Max wattage therefore is 13.1W and 17.5W respectively, though I will assume that both screens are 17.5W. Still though, a completely white screen at max brightness is rather rare.

    There's also, conviniently enough, documentation on how to wire up the panel:

    [21 May: Edit 1]

    So I did some searching, and most high end monitors are essentially around 2000-2400 dimming zones. Now, that sounds like a lot more than 1792 zones that I'm planning to use here, but remember that doubling the zones would only change the backlight resolution from 32x56 to 45x80, so blooming is only marginally reduced.

    Ideally, I'd use a P1.25 to really get a resolution increase, but AliExpress doesn't have a compatible size. The best I could find was P1.875 240 x 120mm, where the excess 240 x 40mm would act similar to the LED module on the Framework 16 laptop.

    As I was wrapping up my search, I did see a panel that specifically claimed "high brightness":

    And it's totally true! 3.5K nits! HDR1000 is actually a possibility, potentially even Liquid Retina XDR*?

    *1600nits peak brightness

    [25 May: Edit 2]

    There's almost no information about how I'd actualy go from an input video signal to a mini-LED LCD, but I just found this paper from 2009: https://sid.onlinelibrary.wiley.com/doi/epdf/10.1002/j.2637-496X.2009.tb00174.x

    • The paper mentions everything from DCR (0D dimming) to 2D colour dimming (RGB LED matrix).
    • RGB has a higher colour gamut and slightly lower power consumption than a white matrix.
    • I need to modify the image...
    Read more »

  • [E2][R] 5G Celluar Connectivity

    kelvinA05/17/2023 at 12:45 1 comment

    Due to the fact that there hasn't been a device productive enough to use outside, I've never looked into celluar data plans. Now that I'm thinking about Leti, I thought I'd look into the inital and running costs of 4G and 5G connectivity.

    Initial Cost

    For an integrated system, the modules designed for the Raspbery Pi CM4 seem to be the most ideal due to its small size and internal USB header.

    As you can see, the 5G price is around 5X the price of the 4G module. It seems that the price is porportinal in some way to the maximum bandwidth supported. For both, the max 3G speeds are 42 download and 5.7 Mbps upload.

    • 4G Modem (CAT4-EU)
      • Fixed (i.e. you have to replace the entire module if you want a new celluar modem)
      • LTE-TDD and LTE-FDD: 150 Download, Upload 50 (Mbps)
      • GPS options are £37.35 and LTE-FDD drops to 130 / 30ish
      • Bands: 
        • B1/3/5/8/34/38/39/40/41
    • 5G Modem (FM160-EAU)
      • Adjustable, but the USB 2.0 connection limits speeds to 310Mbps symmetrical
      • 5G has a standalone (SA) and non-standalone (NSA) version, where it sounds like the latter doesn't support the lower latency improvement of 5G as it uses a mix of 5G and 4G.
      • 5G SA: 2500 Download, 900 Upload 
      • 5G NSA: 3500 Download, 555 Upload
      • LTE: 1600 Download, 211 Upload
      • The Rm500U-CN is cheaper (£104), but support much fewer bands.
      • Bands: 
        • B1/3/5/7/8/20/28/32/38/40/41/42/43
        • n1/3/5/7/8/20/28/38/40/41/75/76/77/78

    Now, I watched this video:

    My takeaways are two things:

    • You pay the same amount for the service, whether you get 30Mbps downloads of 300Mbps downloads, so you might as well try and maximise the reception.
      • This is unlike traditional broadband, where a 200:20 link would cost notably more per month than a 100:10 or 54:5 link.
    • Semidirectional antennas can achieve faster speeds than omnidirectional ones, such as in smartphones.

    Assuming that Leti doesn't fall in a puddle or something, it's probably safe to assume that the celluar modem could be used for 10 years. With that in mind, it sounds like it's better to spend the higher initial cost for 5G and then swap out the board for a USB 3.0 capable one if and when it becomes available. Right now, the averages of all but Three-powered networks are well under the 300Mbps cap:

    It'll be higher in specific areas obviously, but those areas are usually city centres and I'm not going to spend all this dev time to (only) stay inside in someone elses building. I'd assume that the large antennas bundled with the 5G modem will get a notably better signal than from a smartphone, due to the laws of physics. Also remember that the 5G modem allows for much faster 4G connection speeds too, which has very high coverage in the UK these days. 100:10 is the best interet I've used daily, so if I could get 300:200 on Celluar, that'll be immense and could help justify the service contract that I talk about below.

    Another thing is that the listing is actually the cheapest one for a europe-band module that supported USB3.0 that I could find anyway.

    [22 May: Edit 2] I've just found the WS15, a £16.66 USB3.0 module which is probably as small as such a device could ever get. 

    The PCB is 67.5 x 30mm and the USB3.0 port sticks out by another 15mm. It also, suprisingly enough, has the schematics in the listing:

    From this schematic, I can confirm that I can power the thing from 5V. The listing made that a bit confusing, mentioning that it could run on 3.7 or 4.2 volts.

    Moving onto module research, it seems that the RM520N-GL is a suitable alternative to the FM160-EAU. If anything, it's better since it's a global 5G module.

    • 5G SA: 2400 Download, 900 Upload
    • 5G NSA: Download 3400 Download, 550 Upload
    • LTE: Download 1600 Download, 200 Upload
    • Bands:
      • B1/2/3/4/5/7/8/12/13/14/17/18/19/20/25/26/28/29/30/32/34/38/39/40/41/42/43/46/48/66/71
      • n1/2/3/5/7/8/12/13/14/18/20/25/26/28/29/30/38/40/41/48/66/70/71/75/76/77/78/79...
    Read more »

  • [E6][R] Initial Project Research

    kelvinA05/17/2023 at 11:19 0 comments