Second Place Winner ($750.00) - Philip Pemberton (Leeds, United Kingdom)
Notes from the judges:
- This was simply a good idea. It is small, fast and power can be switched to a battery power supply for portable use.
- Using the LCD from a cell phone combined with a standard RAM chip from old PCs makes the hobby cost for this next to nothing.
Downloads:
All files and information © 2005 Philip Pemberton.
Project Description:
Over the past few years, microcontroller-based electronic devices have been rapidly increasing in complexity. That still leaves one major problem – how do you debug a complex digital circuit when it inevitably fails to work? In response to this problem, logic analyzers have started to appear. The only real problem with commercially-made analyzers is that they’re expensive. Not only that, but for many situations they’re just too powerful. That and most of them tend to be rather bulky, not to mention heavy.
As a result of this, I have designed a small, low cost, battery-operated (or AC-powered) logic analyzer that can be recharged and taken anywhere it is required. A Ubicom SX28AC microcontroller supervises the operation of the analyzer, generating control signals for the acquisition circuitry and the LCD display. The LCD used in the prototype was salvaged from a faulty Nokia 3310 mobile phone.
to reduce the size of the final device, the triggering circuitry has been replaced by a single 0V/5V trigger input. This can be configured to be active-high or active-low, or it can be disabled entirely (the SX starts sampling immediately, without waiting for a trigger). The TMODE pushbutton is used to select the desired trigger mode.
To start an acquisition cycle, press the RUN pushbutton. The SX will display a marker in the top-right corner of the display and wait for the trigger signal to go active. After the trigger signal has been received, 256 bytes of data are captured and the SX sends the first 84 bytes of data to the display. The sampled data can be scrolled using the LEFT and RIGHT pushbuttons. It is also worth noting that the RAM chip used in the prototype (IC3) is a high-speed cache SRAM (also known as a Tag RAM) used in many 486 and Pentium motherboards. It can, however, be replaced with a normal 70nS SRAM if the acquisition loop is slowed down (e.g. by adding NOP instructions).
Bill of Materials:
|
ID |
Description |
|
C1-C4 |
0µ1 ceramic decoupling capacitors |
|
C5 |
10µ 16V axial electrolytic capacitor |
|
C6-C9 |
0µ1 ceramic decoupling capacitors |
|
C10 |
0µ22 ceramic decoupling capacitor |
|
C11 |
0µ1 ceramic decoupling capacitor |
|
C12-C13 |
22pF ceramic capacitors (select to match XT1 load capacitance) |
|
CN1 |
2-pin male 0.1” connector (Molex KK or similar) |
|
D1-D5 |
1N4148 – Silicon small-signal diode |
|
D6-D7 |
Red LEDs |
|
IC1 |
SX28AC/DP – MCU, DIP28, 75MHz |
|
IC2 |
74HCT4040 – 12-bit binary counter, DIP16 |
|
IC3 |
W24129A – 16kByte high-speed cache SRAM, 0.3” DIP28 |
|
IC4 |
74LS241 – Dual 4-bit tri-state buffer |
|
IC5 |
74HCT573 – 8-bit data buffer |
|
LCD |
Nokia 3310 LCD |
|
Q1 |
BC547 – Silicon NPN transistor |
|
R1-R8 |
1kΩ ¼W resistor |
|
RP1 |
8x1k 9-pin resistor array |
|
SW1-SW5 |
Momentary SPNO pushbutton switches, e.g. ITT Cannon D6 series |
|
XT1 |
50MHz oscillator crystal |