cys

The homebrew_mini2 board is now a shared project at Osh Park. You can build your own HB_mini2 by ordering the board, here.

 

The parts list is as follows:

 

   z1/z2/z3 TVS diode 12vwm 250vc 0402 F2862CT-ND

 

   CONN USB MICRO B RECPT SMT R/A 609-4613-1-ND

 

   C7 CAP TANT 10UF 10V 20% 0603 718-1673-1-ND

 

   CONN IC SOCKET 24 POS DIP 30AU A35058-ND

 

   F1 PTC RESETTABLE 6V, .500A SMD 0805 F2772CT-ND

 

   Y1 CRYSTAL 25MHZ 18PF SMD 535-9128-1-ND

 

   IC1 IC REG LDO 5V .8A 8SOIC MC33269D-5.0GOS- ND

 

   IC2 IC REG LDO 3.3V 0.5A TSOT23-5 576-1910-1-ND

 

   ICU IC MCU 32BIT 1MB FLASH 64LQFP 497-11767-ND

 

   SWITCH TACTILE SPST-NO 0.05A 12V SW1104CT- ND

 

   7 x C 100n 0402

 

   3 x C 2u2 0402

 

   2 x C 18 pF 0402

 

   1 x C 1 uF 0402

 

   2 x R 40K 0402

 

   2 x R 22R 0402

Below is the schematic for my homebrew mini2 in case anyone finds it useful. My design criteria were: I) incorporation of an STM32Fx chip to allow usage of the netduino 2/netduino plus 2 firmware, and II) all pins compatible with my dive computer/rebreather controller project pcb & associated parts developed with the netduino mini. Through the iterations I've had to solve a USB cable grounding issue and shuffle pins around several times to get backwards compatibility. The last iteration I left pins 2, 3 and 22 disconnected because I had everything I needed elsewhere and wanted to save a little time routing. I just finished chasing down a side effect bug with my 24 bit ADC. The HB mini2 v1.10 has been robust so far, and both the HB mini2 and the netduino mini are now interchangeable on my project pcb. 

 

homebrew_mini2 by cys1, on Flickr

 

(Note: The housing is a slightly modified commercial one that was convenient to use so I could focus on the electronics inside).

I did finally manage to get pin 1 functioning for i/o. It does +/-6V. Adding a public const GPIO pin for PA28/DTXD in NetduinoMiniHardwareProvider.cs got it going, finally. However, I'm stuck using firmware 4.1 as my app is balking with 4.2. Since I haven't been able to get my hands on the 4.1 SDK source yet, I used the 4.2 SDK source to make the 4.1 library by removing "public static class AnalogChannels" and "public static class PWMChannels."

If you have a way of getting the 4.1 SDK source to me, please send me a pm and I'll send you my e-mail address; I only need the "SecretLabs.NETMF.Hardware.NetduinoMini" folder.

As far as processing the DTXD pin 1 signal into something useful, that was pretty easy -- three 10K resistors and one transistor. Pin 1 is now successfully controlling a solenoid (ie the processed pin 1 signal is feeding into a Darlington transistor/diode/cap setup).