I have seen these very cheap logic analyzers for sale for a long time,17 yuan, and it comes with a USB cable and Dupont wires. I was curious about how they managed to do this, so I bought a set to disassemble.
There are10 pin headers, with a total of8 channels, plus one CLK and GND signal. It is marked as 24MHz, and if this data is not exaggerated, it can only measure UART and I2C, but it is powerless for higher-speed SPI.
The signal interface uses this type of horn socket, which contains 2x5P 2.54 pitch pin headers.
The USB port is still the ancient MINI USB port. However, I must say that this type of connector is sturdier than Micro USB connectors.
Upon disassembling to examine the circuit board, the chip is the main character and highlight, the Cypress CY7C68013A-56LTXC, which is a 51 core microcontroller with a high-speed USB controller, with a maximum clock frequency of 48MHz.
Interestingly, the price of this chip on the Lichuang Mall is 27+.
On Taobao, there are two price ranges, one similar to Lichuang’s and another priced at 10-15.
There is a 24C08 on the board, used to store some configurations. I2C communication pull-up resistor 2.2K.
From this perspective, 8 input channel signals come in, passing through a series of 100 ohm resistors before entering the CY7C68013A chip, while a 100K pull-up resistor is also added at this node.
Mini USB connector close-up.
Upon closely examining the soldering of this main control chip, I found that the bottom and PCB are not tightly bonded, QFN pins should have solder wicking, but in reality, it did not wick well. The SMT process for other chips looks quite good.
Interestingly, when I found the download link for the upper computer software from the product detail page and intended to download the software, I discovered that the download link redirected to some messy and even illegal websites. I decided not to try it, as even if 24M could actually work, it wouldn’t be very meaningful. However, for beginners, measuring some IO actions, UART, I2C, and other simple communications should still be somewhat useful, and the biggest advantage is that it is cheap, reducing the learning cost!
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