The tester was originated
here, and continued
here. I got a version of the tester, LCR-T4 for $6.39. It was reviewed by Dave of EEVblog
here. It uses AVR ATmega328P (8MHz) with a 128x64 LCD with back light. The closest schematics is
one here. 78L05 regulates 9V battery to 5V and TL431 provides 2.5V reference. One push button is used for user control and selection and the 14-slot ZIF socket is convenient for different pin spacing.
It can identify and measure a number of 2 or 3-terminal devices and gives reasonably accurate readings Another attractive aspect is that it can be reprogrammed (through the 6-pin header). The source code is
available. One issue is the variety of the boards with slight differences, especially the LCD interface. It appears that this one uses 4-wire interface,
- PD0 - RST, reset
- PD1 - A0, command/data
- PD2 - SCL, serial clock
- PD3 - SI, serial data
Chip Select does not seem connected to any pin, probably grounded.
Install gcc-avr and avr-libc to build the code with the makefile in mega328_T4_v2_st7565. avrdude is used to flash the microcontroller. The old AVR ISP with RS232 interface is supported, choosing avrispv2 as the programmer type. For AVR JTAGICE3, the programmer type is jtag3isp. Press the button while flashing. Also we can use an arduino board as a programmer when flashed with ArduinoISP. The programmer type is avrisp. The 6-pin programming header can be connected together except for the reset pin, which goes to D10.
See
here for a list of software features.
