My name is UNO. UNO R4

There have been many attempts to modernize the UNO family boards. And I think this one is finally fully successful. Why?

The microcontroller from RA4M1 series (from Rensans) was chosen as the board heart. It is a 32-bit unit, with a 48 MHz clock in the popular Arm Cortex M4 architecture. It has an FPU, which means that slightly more complicated floating-point calculations should not be a problem.

The board still maintains compatibility with extensions - it has connectors and a size compatible with R3. But there have already been many such, what distinguishes the UNO R4 Minima is the fact that although the architecture is modern Cortex M4 (modern compared to ATMega328 in previous UNOs), it still works “on 5V”. And we are not talking about power supply here, but about all IO pins! So you can use it with (almost) all shields that were for the old UNO.

The only difference to the detriment of R4 is the fact that while the IO operating voltage could be set to 5V, the newer architecture causes the maximum IO pin current to be 8 mA (the old UNO could 40 mA). So as long as the shield does not draw more than 8 mA anywhere on IO - you can use it.

What for those megahertz, who need that?

Well, yes, there are people who cannot be convinced by anything. But, changing to R4 is not change for the sake of change. Many people working on UNO at some point, when the project grows, encounter a barrier of possibilities. Sometimes it can be bypassed with smarter code (this applies especially to memory problems), but this is not the rule.

R4 Minima has 256 kB Flash memory, 32 kB RAM memory and 8 kB EEPROM. There’s already a big difference here. But, the aforementioned FPU - for floating-point calculations R4 is in a different league. Also additional systems - RTC (clock), DAC - digital analog converter, CAN bus, ADC converter has 14 bits of resolution (and not just the modest 10 bits of ATMega). USB 2.0 and the ability to detect touch (capacitive touch sensing unit)

• RA4M1 processor
• Native USB
• Operating voltage: 5V
• External supply voltage: 6-24V
• Digital I/O outputs: 14
• Number of digital outputs with PWM support: 6
• Number of analog inputs: 6
• Current efficiency per I/O pin: 8 mA
• Flash memory: 256 kB
• RAM memory: 32 KB
• EEPROM memory: 8 KB
• Operating frequency: 48 MHz