In my last projects, I always use the same CPU. DSETA board, I say in the posts. Well, here it is, a CPU based on the AT89C51RE2 microcontroller from Atmel. I develop this board for some reasons. The first and main one is because I want to have a small board with a great (an known) 8-bit microcontroller, ready to use and with many of the peripherals I usually use. The other reason is that I want to test the PCB service from Seeedstudio, a PCB manufacturer from Shenzhen, China. Here are the results.
The Hardware: The schematics of this board can be found here: DSETA CPU Scheme. There’re many pages in the design: I like to divide schematics in functional blocks, and I usually use one (or more) pages to each block, independently of the number of components. Here’s a brief description of each block:
Power Supply: Based on the MC33269DT low dropout voltage regulator. Output is fixed to 3.3V, and with 1.0V dropout, is perfect for a 5V input from USB port. This input voltage can be find in the output connector. This allows power other boards with these 5V or power this board with an external +5V and don’t use the USB port. A green led (D1) indicates the board is powered.
Microcontroller: AT89C51RE2, from Atmel. The core of the board. I select this device for some reasons. Mainly, because I work with this family some time ago, and I’ve a great experience with this chips. I know the internal architecture (it’s an improved 8051 core), and I’ve experience with the Keil C51 compiler. This device has many features: It’s compatible with the 8051architecture, ISP that allows programming in circuit using standard VCC, and a high speed architecture: it can run up to 60MHz. Flash memory is up to 128 KB, and it has a 8KB expanded RAM. The rest of the features can be found in the datasheet. Here in Spain, you can find this chip for less than 4€.