This project is used to connect Android device with STM32 using Android ADK(2011).
The demokit of orignal ADK use Arduino ADK or Arduino with USB Host Shield. The object is
porting Arduino USB host shield to STM32 using STM32F070 Nucleo.
USB host shield need to provide power to device. We need to configure the Nucleo board using external power.
- JP1 off (Disconnect USB power from PC)
- JP5 connect 2,3 pin, using E5V.
We will provide 7-12V from the VIN pin of Arduino Connector(CN6 pin 8)
Using STM32 CubeMX configure the Arduino pinout for USB Host Shield.
| CPU Pin | Arduino PIN | CN5 pin |
|---|---|---|
| SPI1_SCK (PA5) * | D13 | 6 |
| SPI1_MISO(PA6) | D12 | 5 |
| SPI1_MOSI(PA7) | D11 | 4 |
| MAX3421E_SS(PB6) | D10 | 3 |
| MAX3421E_INT(PC7) | D9 | 2 |
| MAX3421E_GPX(PA9) | D8 | 1 |
| CPU Pin | Arduino PIN | CN9 pin |
|---|---|---|
| MAX3421E_RESET(PA8) | D7 | 8 |
PA5 was used as LED in Nucleo board. Since SPI1_SCK is output, it should be OK just leave the LED connected. If not, disconnect the SB21 at the back of board.
| Power Pins | Arduino Pin | CN6 Pin |
|---|---|---|
| VIN (7-12V) | VIN | 8 |
| GND | GND | 6-7 |
Download orginal Android ADK library from [this link.] (https://android-review.googlesource.com/admin/repos/device/google/accessory/arduino)
I bought my USB Host Shield from China. This hardware version has 2 features that is not the same as sparkfun's.
-
doesn't have hex converter to convert 5V to 3.3V level. It uses two resistors(470 and 1000 ohm)for each SPI signal to divide voltage.
Also it could be unstable with 3.3V CPU like STM32. -
MAX3421E reset signal connect to Arduino RESET pin. Sparkfun version use IO pin to control it.
- Remove all 1000 ohm resistors for SPI signal.
- reconnect the MAX3421E_RESET to Arduino pin D7, CPU(PA8).
-
unsigned int data size problem variable size in Arduino is different from STM32. unsigned int should be changed to uint16_t in STM32.
This is important especially in definition of USB packet. -
anonymous union in Keil
In Keil, need to specify #pragma anon_unions before the anonymous union definition in usb.hpp.
-
global class initialization to control IO pin
The c++ global object initialization is done before the __main is executed. So if the code in the initialization use HAL library(GPIO or SPI),to control IO pins, for example, it is not initialized yet.