Dirt cheap hardware is available for developing 8051 microcontroller applications. Such is well suited for students and budget-limited experimenters alike. This minimum system development board kit is available on eBay at a cost of only $3.25 including shipping (from China) –this is a GOOD DEAL! Also a good deal are the AT89S52-24 microcontrollers themselves at $2.99 per pair, free shipping (also from China). One good thing about China is that they ship virtually anywhere. This is a must for the serious experimenter. There are yet more pieces (also inexpensive) required for working with this microcontroller –this subject will be covered in future discussions.
No documentation –is what a minimum development system consists of? This seems typical for this item and I could find no schematic on the web. As a result, I traced out the circuit and drew the schematic.
Thru-hole boards are very easy to assemble –this took about 30min. The only issues were the orientation of the LED and resistor pack. The cathode of the LED is identified by the flat spot. The common pin of the resistor pack is identified by a diamond symbol on one end.
The switch (push On, push Off) is a convenient means of controlling the power and also resetting the microcontroller.
10 position connector
The 10 position ribbon cable connector is the standard Atmel ISP (In-System-Programming) connector. This same connector is also used with the higher level AVR device. Sometimes an alternate 6 position ISP connector is used, but this will not be covered in this discussion.
Omitted is any semblance of a 5V bypass capacitor. While it may work OK without, it is definitely poor engineering practice. I installed a 0.1uf chip capacitor (size 1206) between two traces –see photo. Also, R3 should be 10K rather than the supplied 1.5K –this is easy to fix.
Getting it up and running
This was not trouble-free, but the problem was with the programmer and power source rather than the development board –will discuss this issue in the next discussion.
Microcontrollers wrapped in plastic film –not recommended
Plastic film is not anti-static –if you do not believe it, try unrolling some quickly in a dark closet and watch the sparks fly. To prevent static discharge, I unwrapped the film in a moist environment (over a hot tea pot). Note that most types of pressure sensitive tape also generate sparks.
Minimum development board for the AT89S2051
No product is available for this item. It is yet simpler than the AT89S52 board –smaller with a 20pin IC socket and no resistor pack required. Since there appears to be a market for this item, I may design one myself for eBay sales…at least until the Chinese pick up on it –there is NO WAY I can compete with their low prices with the circuit board costing more than their entire kit.
For the future (partial list)
- LED Chaser (basic AT89S52 schematic driving many LEDs)
- AT89 Features
- Assembly code
- Programming tools
- ASM51 assembler software