Summary of OPENRPNCALC: CUSTOM SCIENTIFIC RPN CALCULATOR BASED ON STM32
Anton Poluektov released an open-source scientific Reverse Polish Notation (RPN) calculator built from scratch around an STM32 microcontroller. It targets efficient, everyday scientific use with unique preprogrammed functions, ultra-low power consumption from a single 3V CR2032 battery (about one year runtime), and a Sharp 400×240 monochrome Memory LCD. The design uses an STM32L476RG (Cortex-M4, up to 80 MHz, 1 MB flash, 128 KB SRAM), Panasonic light-touch tactile switches for the keyboard, and is inspired by SwissMicros DM42 hardware but with original firmware and hardware.
Parts used in the RPN calculator:
- STM32L476RG microcontroller (ARM Cortex-M4, up to 80 MHz, 1 MB flash, 128 KB SRAM)
- Sharp LS027B7DH01 400×240 pixel monochrome Memory LCD
- Panasonic light-touch tactile switches (keyboard)
- 3V CR2032 lithium coin cell battery
- Supporting PCB and passive components (resistors, capacitors, connectors) as typical for the custom board
Reverse Polish Notation (RPN) is a popular method for representing mathematical expressions. In this notation, the operator symbol comes after the operands in contrast to the Polish notation, where the operators are placed preceding the operands. For example, the Polish notation for the addition of 2 and 5 is 2+5, while in reverse Polish notation, it is represented as 2 5 +. RPN is suited for lengthy calculations, and this notation leads to faster calculations. This is because the RPN calculators do not need expressions to be parenthesized. Therefore, to perform a typical calculation, fewer operations need to be performed. In addition, the RPN calculator users make fewer mistakes than the other type of calculator users.
Anton Poluektov, a Physicist from France, recently posted his custom open-source scientific RPN calculator. It is based on an STM32 microcontroller and can operate on a 3V CR2032 lithium battery for around a year. Anton says that the hardware is inspired by the SwissMicros DM42 calculator, but it has been designed from scratch. He further adds to it,
Firmware-wise, however, there is no intention to simulate programmable HP series. Instead, I aim to create a device that fits my everyday needs at work, with a preprogrammed set of functions that are, possibly, rarely or never available in the commercial calculators.
The device has an STM32L476RG ultra-low-power microcontroller. The microcontroller consists of a high-performance ARM Cortex-M4 32-bit RISC core operating at a frequency of up to 80 MHz. The STM32 microcontroller features high-speed memories (1MB flash memory and 128kB of SRAM) and an integrated LCD driver making it suitable for usage in calculators. The display is the Sharp 400×240 pixel monochrome LS027B7DH01 Memory LCD module. It is a TFT-type display with high longevity. The keyboard uses light-touch tactile switches from Panasonic, and the device runs from the 3V CR2032 lithium battery like most modern calculators. Anton mentions that it is sufficient to provide power to the calculator for around one year of operation.
Read more: OPENRPNCALC: CUSTOM SCIENTIFIC RPN CALCULATOR BASED ON STM32
- What microcontroller is used in the calculator?
The calculator uses an STM32L476RG ultra-low-power microcontroller with an ARM Cortex-M4 core. - How long does the calculator run on a CR2032 battery?
Anton states the 3V CR2032 lithium battery is sufficient to power the calculator for around one year of operation. - What kind of display does the device use?
It uses a Sharp 400×240 pixel monochrome LS027B7DH01 Memory LCD module. - Are the keyboard switches mechanical or light-touch?
The keyboard uses Panasonic light-touch tactile switches. - Is the design copied from SwissMicros DM42?
The hardware is inspired by the SwissMicros DM42, but it has been designed from scratch. - Does the firmware aim to simulate programmable HP series calculators?
No, there is no intention to simulate programmable HP series; the firmware aims to provide a preprogrammed set of functions for everyday work. - What are key memory specifications of the microcontroller?
The STM32L476RG includes 1 MB of flash memory and 128 KB of SRAM.
