In this post, we’ll see how to make an SD card reader shield for the Arduino. It’s pretty simple as it’s just a matter of connecting the proper Arduino pins to the correct pads on the SD card adapter. Additionally, resistors need to be added for certain pins. These will form voltage dividers that will drop down the signal voltage for the SD card from 5V to around 3.3V.
In this post, I’ll show my DIY SMD vacuum pickup tool. I bought this vacuum pump SMD pickup but it had no way to be turned on/off. There is only a hole on the vacuum “pen” that you can cover with your finger to make or release the vacuum. I decided I would mod it and make it operable with a footswitch. When pressed the vacuum pump is turned on and when you let go the vacuum pump is turned off while the valve is opened at the same time to release the vacuum and instantly drop the SMD part from the nozzle.
In this post, I’ll show my DIY solder paste dispenser. It’s powered by a 12V adapter and can be operated by a footswitch(connected via banana connectors). It uses a small membrane air pump/compressor to dispense the solder paste/flux. Additionally, there is a solenoid air valve connected to the airline so the pressure can be released after you let go of the footswitch which prevents the solder paste or flux from oozing out. The pump and valve timing is controlled through a relay module by an attiny45 microcontroller.
In this post, we’ll take a look at the inputs and outputs of my 8-bit computer.
In this post, I will talk about the ALU and the flags register of my 8-bit computer. The arithmetical logical unit(ALU) is where all the computation happens in a computer. The ALU of this computer is very simple and only has the option to add or subtract numbers. So something like multiplication would have to be implemented in software. The flags register stores the Carry(a carry occurs) and Is Zero(the result is a zero) flags that it receieves from the ALU.
In this post, we’ll take a look at the button debounce module of my 8-bit computer. Ben used a 555 timer in his clock module to make a delay to debounce the button. I took a different approach. I took the 50 MHz input from the crystal oscillator and lowered the frequency by using another clock module. This way I have another slower clock signal independent from the main clock. This slow frequency is then fed into the debounce modules.
In this post, we’ll take a look at the clock module of my 8-bit computer. Ben used a 555 timer in his clock module to generate the clock signal for his breadboard computer. The approach I took is a bit different. The DE0 Nano FPGA development board has an onboard 50 MHz crystal oscillator connected to one of the pins of the FPGA. This is where we can get our clock signal from. The problem is that the frequency is way too high for the computer and needs to be lowered. This can be accomplished by dividing the frequency using a frequency divider(which is esentially just a ripple-carry counter) or by using a PLL(phase locked loop).
In this post, we’ll take a look at the program counter of my 8-bit computer. The PC(program counter) is used to store the memory address of the next instruction to be executed. After the instruction was executed it the value in the PC will be incremented by one, therefore, pointing at the next memory address that contains the next instruction. The PC is almost identical in construction to the microinstruction counter as both of them are just ripple-carry counters.
In this post, we’ll take a look at the control unit of my 8-bit computer. Ben used an EEPROM to make the control unit in his computer. This is a quite clever approach if you are building your computer on a breadboard as it drastically decreases the complexity, amount of components and space needed. But in my case, it was much easier to just implement the control unit using discrete logic gates.
In this post, I will describe how I implemented the RAM in my 8-bit computer. The RAM size is very small, 16 cells(words) each one with 8 bits. It’s a small and simple computer so a program and its variables will be directly loaded into memory using a programmer. Results and any temporary variables are also all just stored in RAM. The only exception is if you want to output a value you can directly load it into the output