output readings from a Griffin PowerMate USB on osx

README.md

I was toying around with my PowerMate USB on the Mac.

I noticed that in the PowerMate application, you can set triggers for mouse wheel scrolling. But some applications coughMAMEcough don't pick it up.

Investigating I found that it provides its spinner as a uncommon HID type. So applications ignore it, not knowing how to handle that.

The click is presented as a normal button though. So no big deal there.

1. brew install libusb
2. brew install hidapi
3. gcc -o hid_browser hid_browser.c -I/usr/local//Cellar/hidapi/0.8.0-rc1/include/hidapi/ -lhidapi
4. ./hid_browser

Hershwild:~ jstillwell$ ./hid_browser 
Manufacturer String: Griffin Technology, Inc.
Product String: Griffin PowerMate
Serial Number String: 
Feature Report
   00 00 00 f2 01 04 

hid_display.c

#include <stdio.h>
#include <stdlib.h>

#include "hidapi.h"


int main(int argc, char* argv[])
{
  int res;
  unsigned char buf[65];
  #define MAX_STR 255
  wchar_t wstr[MAX_STR];
  hid_device *handle;
  int i;

  /*
  // Enumerate and print the HID devices on the system
  struct hid_device_info *devs, *cur_dev;
  
  devs = hid_enumerate(0x0, 0x0);
  cur_dev = devs; 
  while (cur_dev) {
    printf("Device Found\n  type: %04hx %04hx\n  path: %s\n  serial_number: %ls",
      cur_dev->vendor_id, cur_dev->product_id, cur_dev->path, cur_dev->serial_number);
    printf("\n");
    printf("  Manufacturer: %ls\n", cur_dev->manufacturer_string);
    printf("  Product:      %ls\n", cur_dev->product_string);
    printf("\n");
    cur_dev = cur_dev->next;
  }
  hid_free_enumeration(devs);
  */


  // Open the device using the VID, PID,
  // and optionally the Serial number.
  handle = hid_open(0x077d, 0x0410, NULL);

  // Read the Manufacturer String
  res = hid_get_manufacturer_string(handle, wstr, MAX_STR);
  printf("Manufacturer String: %ls\n", wstr);

  // Read the Product String
  res = hid_get_product_string(handle, wstr, MAX_STR);
  printf("Product String: %ls\n", wstr);

  // Read the Serial Number String
  res = hid_get_serial_number_string(handle, wstr, MAX_STR);
  printf("Serial Number String: %ls", wstr);
  printf("\n");

  // Send a Feature Report to the device
  buf[0] = 0x2; // First byte is report number
  buf[1] = 0xa0;
  buf[2] = 0x0a;
  res = hid_send_feature_report(handle, buf, 17);

  // Read a Feature Report from the device
  buf[0] = 0x2;
  res = hid_get_feature_report(handle, buf, sizeof(buf));

  // Print out the returned buffer.
  printf("Feature Report\n   ");
  for (i = 0; i < res; i++)
    printf("%02hhx ", buf[i]);
  printf("\n");

  // Set the hid_read() function to be non-blocking.
  hid_set_nonblocking(handle, 1);

  // Send an Output report to toggle the LED (cmd 0x80)
  buf[0] = 1; // First byte is report number
  buf[1] = 0x80;
  res = hid_write(handle, buf, 65);

  // Send an Output report to request the state (cmd 0x81)
  buf[1] = 0x81;
  hid_write(handle, buf, 65);

  // Read requested state
  res = hid_read(handle, buf, 65);
  if (res < 0)
    printf("Unable to read()\n");

  // Print out the returned buffer.
  for (i = 0; i < res; i++)
    printf("buf[%d]: %d\n", i, buf[i]);

  return 0;
}

Turns out that you can get usb-utils for the mac (there is a port), and the lsusb command works great to dump the hid descriptors.