Huge thanks to Stefan for his valuable contribution to the upstream of KMK! If you own Macro Pad 10, Knobs 3, and Knob 1, please consider upgrading the KMK firmware on your mini mechanical keyboard to get his fix.
In other news: the GitHub pull request that adds support for ANAVI Knobs 3 was finally merged in QMK! QMK stands for Quantum Mechanical Keyboard. It is probably the most popular firmware for mechanical keyboards and supports literally hundreds of devices, including ANAVI Macro Pad 8 and our other mechanical keyboards. The source code is available under GPLv2 license and written in C. Initial support for the Raspberry Pi RP2040 microcontroller in QMK was added in September 2022. We started the porting efforts in October, and shortly after that, patches for ANAVI Macro Pad 10 and Knob 1 were merged. However, it took almost 6 months to merge the GitHub pull request for ANAVI Knobs 3. The long wait is over: now all of our mini mechanical keyboards are supported by QMK!
The community is very important and makes all the difference in any open source project. Thank you for supporting and improving our open source hardware mechanical keyboards!
As part of the certification program, OSHWA ensures that the definition of “open source hardware” used by a specific project (in our case in these 3 mini mechanical keyboards) matches the community’s definition of open source hardware. They provide a unique identification number (UID) for each version of the certified open hardware device based on the country code and a number. So now we have:
The prefix BG is the country code for Bulgaria, because all these mini mechanical keyboards are made in my hometown of Plovdiv, Bulgaria. As truly and entirely open source projects, we also go one step further. Only free and open source software has been used to design the printed circuit board, the stickers, the firmware, and the documentation. In previous updates we explained how we use KiCad for designing the printed circuit boards and the open source firmware QMK and KMK written in CircuitPython.
Happy New Year and best wishes for 2023! January starts with good news. All Macro Pad and Knobs kits were shipped to Crowd Supply’s warehouse for distribution.
In the coming weeks, all orders placed during the crowdfunding period will enter into Crowd Supply’s fulfillment system and will be processed soon. Shipping to all backers should begin shortly. After that ANAVI Macro Pad 10, ANAVI Knobs 3 and ANAVI Knob 1 will be in stock at Mouser and Crowd Supply.
Thank you for supporting open source hardware products like ANAVI Macro Pad 10, Knobs 3 and Knob 1! W’ll keep posting updates with technical information and we hope you will have a lot of fun with your new gear!
1991 was a remarkable year for computer science and the open source movement. On February 20th, Guido van Rossum released the first version of Python and then, several months later on August 25th, then 21-year old Linus Torvalds announced the first version of what would become Linux. Now, 31 years later, both projects are more popular than ever!
Python is a general-purpose programming language. It supports both object-oriented programming and structured programming which makes Python suitable for a broad range of tasks. MicroPython and CircuitPython are Python 3 variants optimized for constrained devices, primarily microcontrollers. MicroPython appeared in 2014. Three years later, in July 2017, MicroPython was forked into another open source project called CircuitPython. There are some differences, most notably that each of them supports a different set of hardware devices.
A classical mechanical keyboard consists of keys (mechanical switches with keycaps) wired to a microcontoller. There are a huge variety of models, variants, and manufacturers of mechanical switches. For example, the ANAVI Macro Pad 10 comes with Gateron red mechanical switches, but the hot-swap sockets allow you to actually use any other kind of Cherry MX compatible switch. Firmware on the microcontroller maps the keys to specific characters.
In general, a microcontoller has a limited number of GPIO (general-purpose input/output) pins, so the keys are most commonly organized in a matrix. For example, ANAVI Macro Pad 10 is designed with a three-by-three matrix which only requires six GPIO pins instead of nine. The role of the firmware is to detect when a key is pressed and then send a specific character or sequence of characters (i.e., a macro) to the computer.
Ease of use combined with the power of the RP2040 makes CircuitPython a very good programming framework for implementing mechanical keyboard firmware. Of course CircuitPython is not as fast as C. However this is not a problem for the RP2040 because it is a dual-core Arm Cortex-M0+ processor with a clock running up to 133 MHz. Furthermore RP2040 has 264kB on-chip SRAM – more than enough for keyboard firmware. Thanks to the powerful microcontoller, it is easy to get started and customize keyboard behavior directly by altering the CircuitPython source code. There is no need to install complex toolchains or to cross-compile the source code. With KMK, it is easy to edit the source code in CircuitPython on pretty much any operating system, no matter if you are a Microsoft Windows, MacOS or a GNU/Linux user.
As part of the covered stretch goals, each kit will include stickers from ANAVI Technology and KiCad, the free and open source CAD software used for designing the printed circuit boards of the keyboards. Furthermore, ANAVI Macro Pad 10 kits will include 32 super-cool emoji stickers. You can stick them on the top or sides of the translucent keycaps. Last but not least, we’ll be publishing various video tutorials to ensure getting started is easy.
The printed circuit board of ANAVI Info uHAT has a green solder mask and a gold surface finish. There are a few steps more to complete the manufacturing process. An EEPROM has to be flashed and soldered on each board. It will contain software description of the add-on board following Raspberry Pi Foundation’s HAT (Hardware Attached on Top) specifications. After that each board will go through a quality assurance, and finally each kit will be packaged in a recyclable cardboard box.
Low-volume manufacturing is not an easy task nowadays, especially during a global chip shortage. As usual we will keep you updated. Thank you again for supporting ANAVI Info uHAT!
I2C stands for Inter-Integrated Circuit, pronounced eye-squared-C, and alternatively known as IIC. It is a synchronous, multi-controller/multi-target (controller/target), packet switched, single-ended, serial communication bus. This protocol is suitable for devices wired at short distances, no more than 2-3m. We use I2C in pretty much all our open source products: Internet of Things, mechanical keyboards and Raspberry Pi HATs.
I2C was originally developed in 1982 by Philips. While that makes it 40 years old, it is still a very convenient and widely used bus. There are many I2C sensors and peripherals. It is in pretty much every smartphone, embedded electronics, microcontroller, personal computer and of course Raspberry Pi.
Actually, since the introduction of the famous 40-pin header in 2014, Raspberry Pi single board computers have not one but two I2C buses! We use them both on ANAVI Info uHAT and our other HATs. Th first I2C bus is on pins 3 and 5. On the ANAVI Info uHAT, it is used for the three I2C slots for sensors and the 4th dedicated slot for the mini OLED display.
The second I2C bus is on pins 27 and 28 of the Raspberry Pi and is reserved exclusively for attaching an ID EEPROM. The ID EEPROM contains a software description of the hardware so the operating system on your Raspberry Pi can automatically identify the add-on board.
The I2C bus consists of two signals: SDA (Serial Data) is a data signal, SCL (Serial Clock) is a clock signal. I2C modules also need power, so the dedicated I2C connectors on the ANAVI Info uHAT and our other open source hardware provide two additional pins for VCC and GND. Typically, the VCC for the I2C connectors on our add-on boards for Raspberry Pi are 3.3V.
The I2C bus drivers are “open drain”, which means they can only pull the corresponding signal line at low level. They cannot drive it high. To restore the signal to high when no device is asserting it low, a pull-up resistor has to be added to each signal line. For example, on the ANAVI Info uHAT, we have 4.7K pull-up resistors R4 and R5 connected to SDA and SCL.
Resistor selection varies depending on the devices attached to the bus. In some specific use cases, further adjustment of the resistance value might be required. For systems with lots of devices or longer wires, smaller resistors are better.
How to Enable I2C on Raspberry Pi OS
Raspberry Pi OS, previously known as Raspbian, is the default and recommended Linux distribution for all models and versions of the Raspberry Pi single board computer. By default, I2C is not enabled. There are several ways to enable it, but probably the easiest is using the command-line tool raspi-config to perform few basic commands:
Open a terminal or login remotely via SSH to your Raspberry Pi and type in the following command: sudo raspi-config
Each I2C device must have a unique address. The I2C reference design has a 7-bit address space, although rarely it might be used with a 10-bit extension. The 7-bit addresses range from 0 to 127 (0 to 0x7F hexadecimal). This is a limitation because it is not possible to have two I2C devices with the same address on the same I2C bus. For example, the I2C address on the mini OLED display included in all ANAVI Info uHAT kits is 0x3C. From the software side, this address is used in the example Python 3 script to access the display.
For Linux distributions, including Raspberry Pi OS, there is a package with a heterogeneous set of I2C tools called i2c-tools. To install it on Raspberry Pi OS, open a terminal and execute: sudo apt install -y i2c-tools. Once you have it installed, you can list attached I2C devices by their addresses with i2cdetect. For example, if the HTU21 temperature and humidity sensor module is attached to the Raspberry Pi, the output will be:
Thanks to early backers ANAVI Info uHAT was successfully funded and hit its first stretch goal in a just a couple of days. So we’ll be adding some awesome KiCad and ANAVI Technology stickers. KiCad is the free and open source software we used to design this and other Anavi printed circuit boards.
As a small open source project, ANAVI Info uHAT relies on the community of passionate open source makers. We are near our second stretch goal of $1,000. If we hit it, we will make more video tutorials for all supported sensors.
There is still more than a month until the end of the crowdfunding campaign and we hope more people will jump in and order ANAVI Info uHAT!