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Koenraad, Johannes

The Strawberry Cake is a small, cheap embedded ARM board. Unlike the Raspberry Pi, it is real close to exist. It is a board design that challenges you to assemble it yourself, to practice your fine-pitch SMD soldering techniques. It can be assembled with a normal soldering station, or - better - reflow soldered. Ongoing miniaturisation is a FACT, if you want to do electronics without being stuck in the 80's, you need SMD!

It will not run Linux since there is not enough memory, but it will spin circles around arduino's. It is made for the STM32 family members that come in 64pin TQFP packages, and have on-board USB, and optionally SDIO.

It features :

  • a USB mini-B connector
  • a single-wire debug (SWD) connector for ... debugging
  • a micro-SD card slot (only SDIO mode)
  • place for pin-headers
  • on the topleft of the pin-headers a character LCD can be fitted
  • reset button
  • user button
  • two LED's

Compared to an Arduino :

  • it teaches you to build a DIY-professional design
  • can do properly what needed dirty hacks for on Arduino
  • can do dirty hacks that were out-of-reach on Arduino
  • has in-circuit-debugging support (with STLink v2 for example). Arduino can do this too but for some reason nobody does.

Target cost of unassembled pcb + components is 20 EURo's.

Bill of materials:

Qty Value                Device               Parts                            
1                        CRYSTALHC49UP        Q1                        
1                        DIODE-SOD123         D1                                  Farnell: 1510677
2                        LEDCHIP-LED0603      LED1, LED2                       
1                        PINHD-1X5            JP2                                 DNP
2                        PINHD-1X30           JP3, JP5                            DNP
1   1k5                  R-EU_R0603           R4                               
2   2.2u/6.3V            C-EUC0603            C6, C7                           
2   22                   R-EU_R0603           R9, R10                          
2   22p                  C-EUC0603            C1, C2                           
2   22uF                 CPOL-EUSMCB          C13, C14                            Farnell: 1759434
4   100k                 R-EU_R0603           R2, R5, R8                       
8   100n                 C-EUC0603            C3, C4, C5, C8, C9, C10, C11, C12
2   220                  R-EU_R0603           R6, R7                              
2   DTSM-6               DTSM-6               S1, S2                    
1   MICROSD_SD_MODE      MICROSD_SD_MODE      U$2                                 DNP,
1   MINI-USB-UX60-MB-5ST MINI-USB-UX60-MB-5ST X1                                             
1   REG1117              REG1117              IC1                                 Farnell: 1852183
1   STM32F40X-64         STM32F40X-64         U$1                                            
1   ferrite              R-EU_R0603           R1                                  0R