These are
finished calculator projects I have worked on. For projects I'm working on now, see
Current Projects.
Programmable RPN Calculator
This calculator is based directly off of my RPN Scientific Calculator (see below). Rather than two MSP430 microcontrollers with 128k parallel SRAM and shift registers, this calculator uses an LPC1114 with a 128k SPI SRAM for a much more compact design. It uses the same strategy of referring to memory in the 128k external ram with variable names and converting those references to function calls at compile time that I used on the RPN Scientific Calculator. The ARM core running at 48MHz in this calculator offers much faster performance than the MSP430s of the last project. There was also extra room in the flash of this chip, so I added a simple keystroke programming mode. The display is a noritake VFD which looks really great. It consumer around 250ma, so I power the calculator with two 18650 rechargeable batteries. The only thing missing is labels for the keys.
Posts about this project:
Programmable RPN Calculator
RPN Scientific Calculator
This calculator has two MSP430s working in tandem to control the memory, screen, and keyboard. The main memory is 128k of parallel SRAM, which the MSP430 cannot address directly as memory since it lacks an external bus. Instead, I designed a converter program that would let me refer to memory stored externally using arrays then convert those array accesses at compile time to function calls that use the GPIO to read and write data to the chip. The software supports basic math functions, exponents, logarithms, roots, and trig functions. The accuracy of calculation can be set from 12 to 32 decimal places in the settings screen. With 32 decimal places, the calculator produces extremely accurate results. The display is a simple 4x20 HD44780 compatible LCD. While the systems runs at around 3.6v, the LCD expects 5v and sets the contrast relative to the voltage difference between the supply voltage and contrast pin. Luckily, the logic of the LCD will run at 3.5v, so I use a 555 timer to supply around -2v on the contrast pin to make the display visible. The keypad is soldered from 42 tactile switches, and the button labels were cut on a laser printer into stamp rubber and then painted. The case was cut out of a large single sheet of copper clad circuit board material and soldered together into a box. This project was part of
Hacklet 70 on Hackaday and won first place at the
Project of the Month Contest on 43oh in 2014.
 |
Result of asin(acos(atan(tan(cos(sin(9)))))) used
in one calculator forensic to gauge accuracy. |
 |
| Inside view of case soldered out of copper clad. |
 |
Calculator circuit board showing two MSP430 microcontrollers, 128k parallel SRAM,
three shift registers to control SRAM, and 555 timer to generate negative contrast voltage. |
 |
| Schematic of circuit. |
Posts about this project:
RPN Scientific Calculator
Binary LED Calculator
This is the first calculator I built when I got interested in electronics. It shows numbers in binary format using eight LEDS rather than using a screen. In addition to an MSP430 microcontroller, it has two shift registers to drive the LEDs and read buttons presses. As well as addition and subtraction, it has a few simple operations like push and pop. It runs from a 2032 coin cell battery.
Posts about this project:
Binary LED Calculator
This calculator is based directly off of my RPN Scientific Calculator (see below). Rather than two MSP430 microcontrollers with 128k parallel SRAM and shift registers, this calculator uses an LPC1114 with a 128k SPI SRAM for a much more compact design. It uses the same strategy of referring to memory in the 128k external ram with variable names and converting those references to function calls at compile time that I used on the RPN Scientific Calculator. The ARM core running at 48MHz in this calculator offers much faster performance than the MSP430s of the last project. There was also extra room in the flash of this chip, so I added a simple keystroke programming mode. The display is a noritake VFD which looks really great. It consumer around 250ma, so I power the calculator with two 18650 rechargeable batteries. The only thing missing is labels for the keys.
This calculator has two MSP430s working in tandem to control the memory, screen, and keyboard. The main memory is 128k of parallel SRAM, which the MSP430 cannot address directly as memory since it lacks an external bus. Instead, I designed a converter program that would let me refer to memory stored externally using arrays then convert those array accesses at compile time to function calls that use the GPIO to read and write data to the chip. The software supports basic math functions, exponents, logarithms, roots, and trig functions. The accuracy of calculation can be set from 12 to 32 decimal places in the settings screen. With 32 decimal places, the calculator produces extremely accurate results. The display is a simple 4x20 HD44780 compatible LCD. While the systems runs at around 3.6v, the LCD expects 5v and sets the contrast relative to the voltage difference between the supply voltage and contrast pin. Luckily, the logic of the LCD will run at 3.5v, so I use a 555 timer to supply around -2v on the contrast pin to make the display visible. The keypad is soldered from 42 tactile switches, and the button labels were cut on a laser printer into stamp rubber and then painted. The case was cut out of a large single sheet of copper clad circuit board material and soldered together into a box. This project was part of Hacklet 70 on Hackaday and won first place at the Project of the Month Contest on 43oh in 2014.
This is the first calculator I built when I got interested in electronics. It shows numbers in binary format using eight LEDS rather than using a screen. In addition to an MSP430 microcontroller, it has two shift registers to drive the LEDs and read buttons presses. As well as addition and subtraction, it has a few simple operations like push and pop. It runs from a 2032 coin cell battery.
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