MMDVM (Multi-Mode Digital Voice Modem), which translates to "Multi-Mode Digital Voice Modulator/Demodulator" in Chinese.
This version has DB9MAT DF2ET DD7EN available on GitHub as open-source, and products with the original author's name and open-source identifiers removed can be found throughout the seafood market.
Due to the original design using a mini-USB interface and having an unattractive layout, I redesigned the PCB using a four-layer board. (I have a large stock of STM32F103R* chips, so during the redesign, I replaced the MCU with this one. If you are using J-FLASH to download, please select the actual MCU you are using; STM32F103RB is sufficient. Choose the more affordable option.)
The finished product images are shown below:
Since HamCQ cannot upload attachments or videos, please refer to Gerber/Bom and test video files at:
https://www.kechuang.org/t/90284
If STM32 and ADF7021 are used with second-hand components, the overall material cost is approximately 30 RMB per piece (excluding Raspberry Pi). If new materials are used, the material cost will not exceed 80 RMB per piece.
Definition of a "burnable head" (If you want to buy the same type of burnable head, you can search for TC2030)
Appendix: The original open-source link is as follows:
PCB (Hardware):https://github.com/phl0/MMDVM_HS_Dual_Hat?tab=readme-ov-file
Software:https://github.com/juribeparada/MMDVM_HS
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