This is a gpio over usb board based on VUSB stack for AVR atmega8 chip. It exposes 12 GPIO ports.
My current prototype uses USBPrayog Board from rarecomponents.com.
I shall produce an exclusive kicad schematic for this board soon.
cd firmware
make hex
avrdude -c usbasp -p m8 -U flash:w:main.hex
| Atmega8 gpio | pin number |
|---|---|
| PD0 | 1 |
| PD1 | 2 |
| PD2 | Not available (used as D+) |
| PD3 | 3 |
| PD4 | Not available (used as D-) |
| PD5 | 4 |
| PD6 | 5 |
| PD7 | 6 |
| PB0 | 7 |
| PB1 | 8 |
| PB2 | 9 |
| PB3 | 10 |
| PB4 | 11 |
| PB5 | 12 |
| PB6 | Not available (used by crystal) |
| PB7 | Not available (used by crystal) |
| Atmega8 ADC pin | pin number |
|---|---|
| PC0 | 0 |
| PC1 | 1 |
| PC2 | 2 |
| PC3 | 3 |
| PC4 | 4 |
| PC5 | 5 |
You need to load the kernel driver for this.
$ cd driver/gpio
$ make
$ sudo insmod usb-gpio12.ko
$ cd /sys/class/gpio/
gpiochip**N** where N is the value allocated by kernel
$ sudo chmod 666 export unexport
$ echo **N** > export
$ cd gpio**N**
$ echo out > direction
$ cat value
$ echo 1 > value
$ echo 0 > value
Before unloading the module, do $ echo N > unexport
gpioN gets deleted by doing so.
To unload the module, $ sudo rmmod usb_gpio12
In case, you want to control gpio ports via libusb, follow this guide.
include following code in your application code or include the common.h file.
typedef struct __attribute__((__packed__)) _gpio_info
{
uint8_t no;
uint8_t data;
} gpio_info;
typedef struct __attribute__((__packed__)) _gpiopktheader
{
uint8_t command;
gpio_info gpio;
} gpiopktheader;
typedef struct __attribute__((__packed__)) _spipktheader
{
uint8_t command;
uint8_t data;
uint8_t speed; //future;
} spipktheader;
typedef struct __attribute__((__packed__)) _adcpktheader
{
uint8_t command;
uint8_t gpio_no; //C0 -- C5
uint16_t data; //ADC data is 12 bits (0 - 1024)
uint8_t speed; //Future
} adcpktheader;
typedef enum _command
{
BOARD_INIT, // This does the init of board
BOARD_RESET, // This restarts the board
GPIO_INPUT, // Set GPIO as input
GPIO_OUTPUT, // Set GPIO as output
GPIO_READ, // Read GPIO
GPIO_WRITE, // Write to GPIO
SPI_INIT, // Initialize SPI
SPI_DATA, // Send data over SPI
SPI_END, // End spi connection
ADC_INIT, // Initialize ADC
ADC_READ, // Read ADC value from ADC pin (C0 - C5)
ADC_END, // End ADC
} command;- init the board
uint8_t buffer[3];
usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
BOARD_INIT, 0, 0, buffer, 3, 1000);
gpiopktheader *reply = (gpiopktheader *)buffer;- set GPIO as output
uint8_t buffer[3];
usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
GPIO_OUTPUT, gpio_number, 0, buffer, 3, 1000);
gpiopktheader *reply = (gpiopktheader *)buffer;- write to GPIO
high
uint8_t buffer[3];
usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
GPIO_WRITE, gpio_number | (1 << 8), 0, buffer, 3, 1000);
gpiopktheader *reply = (gpiopktheader *)buffer;low
uint8_t buffer[3];
usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
GPIO_WRITE, gpio_number | (0 << 8), 0, buffer, 3, 1000);
gpiopktheader *reply = (gpiopktheader *)buffer;- Read GPIO
uint8_t buffer[3];
usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
GPIO_INPUT, gpio_number, 0, buffer, 3, 1000);
usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
GPIO_READ, gpio_number, 0, buffer, 3, 1000);
gpiopktheader *reply = (gpiopktheader *)buffer;
uint8_t gpio_read_val = reply->val;- Reset Board
uint8_t buffer[3];
usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
BOARD_RESET, 0, 0, buffer, 3, 1000);
gpiopktheader *reply = (gpiopktheader *)buffer;- SPI communication
uint8_t spi_data = 111;
nBytes = usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
SPI_INIT, 0, 0, 0, 0, 5000);
nBytes = usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
SPI_DATA, 0 | (spi_data << 8), 0,
buffer, 3, 5000);
spipktheader *spi_info = (spipktheader *) buffer;
printf("MOSI data: %d", spi_info->data);
nBytes = usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
SPI_END, 0, 0,
0, 0, 5000);- ADC
nBytes = usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
ADC_INIT, 0, 0,
buffer, 1, 1000);
nBytes = usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
ADC_READ, gpio_number, 0,
buffer, 5, 1000);
adcpktheader *adc_info = (adcpktheader *)buffer;
printf("ADC pin %d read value: %d\n", adc_info->gpio_no, adc_info->data);
nBytes = usb_control_msg(handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN,
ADC_END, 0, 0,
buffer, 1, 1000);you can look into ubstest example for more details.
GPIO write speed is close to 1Khz.
write firmwareDONEwrite basic gpio driverDONEAdd support of spin locking in gpio driver.DONE- Add support of spi bitbang driver.
Add support of spi hw in firmware.DONE- Add support of spi hw driver.
- Add support of i2c in firmware.
- Add support of i2c driver.
Add adc support in firmware.DONE- Add adc driver support.
- Add PWM pins support.
- Add PWM driver?.
- Add UART support.
- Add UART ttyUSB driver support.
- design schematic.
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