Here's something I've needed for a long time - a dual USB to UART converter, i.e. one USB connector and two serial ports on the output, and this together with the DTR/RTS flow control signals brought out, which can be used, for example, to reset and control the bootloader mode of external devices. The whole thing can be bought for about a dozen zloty, the price depends on the quantity imported and the online shop chosen.
Like the well-known CH340, this chip gives us a choice between 3.3 V and 5 V logic levels. Also in an analogous way, it has one rather serious shortcoming, namely that it cannot provide a sufficiently large current from its 3.3 V pins for many applications, so if we want to run some Wi-Fi modules with it such as the ESP8266, ESP32 or there BK7231, we need to arm ourselves with an external chip with a 3.3 V LDO, such as the AMS1117-3.3 for example.
The CH342 itself is available in tiny housings such as QFN24 (CH342F) and ESSOP-10 (CH342K). The CH342 requires minimal external components to operate.
The main motivation and 'battle test' for this module was to use it to work with BK7231 , as this chip has two UART ports that are both actively used during firmware development - one is used to display the device activity log and the other for programming. Here are the pictures from colleague @DeDaMrAz :
Unfortunately, however, it was not possible to make the absolute minimum connection, as the Beken would not start without an external 3.3 V supply:
Looks like we're in for an additional 3.3 V LDO hand-soldering to the underside of the board shown. How about finding a module with CH342 and AMS1117-3.3? That would be the best option.
In any case, the UART works fine - the computer immediately sees the COM ports, here for example COM4 and COM7 and we can operate them via Realterm:
In summary , I liked the CH342-based USB-2TTL module very much. Its only downside is the lack of a good LDO on board, which complicates things in some tasks and, for example, makes it difficult to connect the whole thing to a programmable Wi-Fi module. On the other hand, I consider the presence of DTR and RTS lines to be a plus - many cheaper adapters lack this.
Finally, it is worth mentioning that the module is equipped with a modern USB C-type connector, so there is no problem with the orientation of the plug.
Have you used the CH342? What applications do you see for this chip?
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