VOLVO+ Development Story (3), prototype

To make VOLVO+, I used some existing boards to assemble. As a personal developer, there's no HW team to do PCB things, even find IC's FAE to solve problem. I struggled to make each components on PCB working

The 1st item is MCU board, Blue Pill, you can find it easily. The processor can run at 72Mhz, with 64K Flash and 20K SRAM. That means plethora resource to waste :-)

I have to do some reworking to the board

  • Remove power LED to eliminate unnecessary powers (to make low-power measurement precise)
  • Remove the 5v-to-3.3v LDO in the back of board (I used my own power circuit to power)



CAN bus transceiver had 3.3v/5v variant, and it also had distinct low-power performance. Besides, buying IC from China's Taobao is not good idea, I just bought some failure ICs. Here's some ICs that I've tried
  • NXP TJA1050, 5v
  • Microchip MCP2551, 5v
  • TI SN65HVD230, 3.3v
  • TI SN65HVD231, 3.3v
  • Maxim MAX3051, 3.3v



Finally I shall convert 12v to 3.3v to power the board. My power consumption is only 20mA and LDO is ideal to do the conversion. At first I use AMS1117/3.3 to do the prototype, but it had 5mA static power-drain! Finally I found some LDO with only 15uA current drain

I also evaluated buck conversion, but it had mA level static leakage

The board used to try different LDO ICs


This is DC-to-DC buck conversion module, the left down corner had a adjustable resistor to tune the output level level



Assemble all mentioned components together. Some parts were not suitable while some were just broken. The bread board is convenient to evaluate different ICs without soldering. I put both 5v and 3.3v power sources which allows me to try different CAN bus transceivers. The main drawback is larger size (I don't want to use this on my car directly)




Another form of prototype requires some soldering, but the size is smaller. It requires better soldering skill to make the prototype. With some efforts (and retry), I finally make some prototype able to put on my car, and stabilize the HW design









Then I shall design the product appearance and PCB

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