This is a little tamagotchi-like toy I've created for my wife. I used to think that this is how a modern Tamagotchi could look like initially. However, it can also be used as a battery-powered DIY platform to experiment with FreeRTOS and graphics.
Monochrome OLED 128x64px
Low energy consumption (~20mA @ active, 0.75mA @ sleep)
Hand-soldering friendly (TQFP-44 0.8mm pitch, smallest is 0603)
Open Source Hardware/Firmware
ATmega1284P 8-bit AVR MCU with 128 KiB flash and 16 KiB SRAM
I'm going to include a review for PCBWay service as a part of this update because they supported me with the current iteration of Xling v3.2 and manufactured black PCBs for free.
However, I'd like to keep it as fair as possible because everyone should benefit in this case. On one hand, everyone who's reading it will be able to understand what PCBWay is capable of. On the other hand, PCBWay will be able to see what they might improve in their service.
Personally, I'd like to thank DI HALT and his blog, easyelectronics.ru. I read it from time to time with pleasure. Besides, an article about PCBWay helped me a lot.
Let me show you how Xling looks like in its current iteration fully assembled and in a 3D-printed case. Just as I imagined!
How to configure PCB
There are many parameters to tweak in order to quote a PCB production, and some of them might not be obvious enough. I'll try to describe them briefly and spend more time for obscure ones.
Board type parameter means a way to prepare PCBs. You'll receive boards in single pieces in case of the first option which is suitable for prototypes or a small batch production. The second and third options which start with Panel by... might be useful in case of an automatic assembling and a mass production and allow you to select your own size of a panel (Panel by Customer) and let PCBWay populate it with your boards, or let PCBWay to do all of these steps (Panel by PCBWay).
Please, note that in case of a single board it's necessary to select Size of a single board only, but in case of a panel, these are dimensions of the whole panel which might contain several boards. The same rules are applicable for Quantity which means a number of single boards or a number of panels accordingly.
Generally speaking, it's not obvious why somebody would let PCBWay to decide how to panel her boards because dimensions of a panel depend on a specific assembly equipment. However, PCBWay offers an assembly service also and the third option is useful in this specific case.
There are several ways how boards will be connected within a panel. In case of V-ScoringPCB material will be cut for a half of its height to simplify a break off. In case of Tab Route boards will be attached to a panel and among each other by narrow bridges.
It might also be necessary to include different designs into a single panel, but it'll increase its price.
Another option called X-out Allowance in Panel gives an incredible ability to reduce an overall cost of the panel by about 30%. It's useful if you can tolerate a PCB in the panel to fail electrical testing. It'll be marked by a cross in this case.
You shouldn't usually worry about number of Layers because it can be obtained automatically from Gerber files provided within an archive.
Material is what PCB is manufactured from, where FR-4 is epoxy glass cloth (the most widely used material for PCB, probably) and the rest.
Personally, I'd like to mention FR4-TG which stands for a glass transition temperature and defines some thermal and chemical properties of the material. One of the most important things which is affected by this temperature is board geometry which is critical in case of really narrow routes and precision PCBs. The higher the temperature, the better PCBs can be manufactured, but overall cost will be increased also.
Another important option is HDI (Buried/blind vias) which stands for High Density Interconnect PCBs. In this case RCC (Resin Coated Copper) is applied to epoxy glass cloth which leads to fine circuits.
These are limits for tracks/spaces and size of the holes. Please, be careful and select them according to your design.
It's interesting how minimal these options are. For example, you cannot select a limit for annular ring, but a diameter only. Personally, I'd recommend to read about PCBWay capabilities first in order to stay within limits and reduce amount of money to be spent on PCB production.
Almost a month and a half passed since the previous update (not so much comparing to v0.3, eh?) and I'm here to share some details regarding the overall progress.
First of all, I've finally got rid of the leading zero in the Xling PCB version because there are no chances that I'll be brave enough to change it in future. So, v0.3.1 became v3.1 and it means that the most recent changes of the Xling PCB will find their way into current/3.0 branch of the repository.
Note that it has nothing in common with the firmware version of Xling. The most recent changes in code find their way into current/0.4 branch of the Xling-firmware repository
Anyway, I'd like to show you a walking animation demo at 24 FPS. There are only 4 images of the animation where each one stays on a screen during two frames.
The whole summer has passed and I've finally finished the next version of the toy according to my plan. There are several significant changes which you've probably noticed:
The first one doesn't carry any technical function, but provides a unique look and feel of the PCB (many thanks to SierraSaura for this picture).
The second change is a new ATmega1284P MCU which replaces the previous ATmega328P one.
It is the most important improvement over the previous versions because of the 32 KiB -> 128 KiB flash memory (the only memory on the board to carry a lot of the graphic sprites, for example). An amount of RAM has also been increased from 2 KiB on ATmega328P to 16 KiB on ATmega1284P.
The third change is almost the same OLED display which color is white now instead of the yellow on the previous prototypes and connected using SPI.
All of the previous displays with SH1106 controller were connected via two-wire interface (TWI, another name for I2C) which is relatively slow comparing to the SPI.
However, a driver for the SH1106-based displays I'm working on doesn't support SPI yet. This is the next step on my way and this new Xling v0.3 will help me testing it.
Anyway, if you have any questions and ideas on your mind, feel free to tell me then.