Project Logs

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• Week 6. Getting ready to put the hardware together.

  Igor Shturma • 6 days ago • 0 comments

  Everything has now arrived: PCBs, displays, compute modules, components. Time to get hands dirty with the solder paste.

• Week 5. PCBs ordered.

  Igor Shturma • 01/05/2021 at 19:36 • 1 comment

  An exciting milestone in the project was achieved right before New Year's Eve: the design is finished for the first PCB revision, time to order the boards.

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• Week 4. The board architecture is finalized.

  Igor Shturma • 12/29/2020 at 03:21 • 2 comments

  We are now done with the architecture, BOM, and most of the schematic.

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• Week 3. Ordering the display samples.

  Igor Shturma • 12/25/2020 at 01:24 • 1 comment

  Last week we got in touch with nearly 20 display suppliers from China listed on Alibaba. A few of them could offer us our display panel bound with a capacitive touch digitizer. If we order 100 pcs shortly, they are going to cost us around $35 each. We will get five samples in a few weeks. Those are going to be complete modules, with optically clear adhesive bound. No need to buy touch sensors separately anymore. We are also getting an HDMI-MIPI board that we can use to test the displays initially and as a reference, if something doesn't work right.

• ​Week 2.2 Applied for Seeed sponsorship program

  Sasha Shturma • 12/11/2020 at 20:30 • 0 comments

  In October Seeed announced sponsorship of projects that use Raspberry Pi CM4. For those approved, they give $500 towards PCB assembly services. More details on their blog. 
  
  

  We haven’t worked with Seeed before, but this seems like a good opportunity to try manufacturing with them.

• Week 2.1 Choice of the touchscreen.

  Sasha Shturma • 12/08/2020 at 02:57 • 0 comments

  We further narrowed down specs for the touchscreen:

  1. Should use capacitive, multi-point touch technology.
  2. The touchscreen driver IC should be cost-effective, widely available, and have good software support. A GT911 IC from Goodix Technology is a popular touchscreen driver found in many consumer electronic products. It connects over I2C and is supported by mainline Linux. 

  Most display panels are sold without touchscreen because touchscreen glass and framing are customized for specific products. There are plenty of suppliers in China that offer customization and assembly of screen parts together. However, they usually prefer to work with high volume orders. We'll most likely buy a touchscreen for initial testing and glue it with a display panel ourselves. Ideally, this should be done in a cleanroom at a factory, but our simplified approach works for fast evaluation.

• Week1. Choice of the display.

  Sasha Shturma • 12/03/2020 at 23:25 • 0 comments

  Criteria:

  • High-resolution, 
  • 7" diagonal,
  • Bright - 400+ cd/m2,
  • MIPI interface,
  • Costs less than $50,
  • Available off-the-shelf from multiple suppliers.

  We found display panel LT070ME05000 used in Asus Google Nexus 7". Specs look great, so we need to find a supplier with this panel available in a final assembly with hardened glass and touch input.

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