nRF51422 HID example modification

Question

Hello 
 I'm using nRF51422 with S310 softdevice. I've been testing HID example (keyboard) for a while.
What I'm trying to do is to send as much as possible bytes at once in a single report.
I do like this: 
 uint8_t ucData[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

ble_hids_inp_rep_send(&m_hids,
 INPUT_REPORT_KEYS_INDEX,
 INPUT_REPORT_KEYS_MAX_LEN,
 ucData);
 
 All works well until INPUT_REPORT_KEYS_MAX_LEN is not more than 8, otherwise it does not work. So 8 bytes is the maximum for now. 
 My question is: what is the max number of bytes that can be sent at a time and how to do that?
And, of course, the same question applies for receiving side. 
 I have a feeling that report_map_data[] descriptor should be modified, but I don't know how to do that and also I can't find any documentation on this.
Forget mouse, forget keyboard, I would like to make HID as generic as possible. 
 Regards

Nikita · Accepted Answer

You can use custom HID report map like this: 
 #define INPUT_REPORT_MAX_LEN 20 /**< Maximum length of the Input Report characteristic. */
#define OUTPUT_REPORT_MAX_LEN 22 /**< Maximum length of Output Report. */

static uint8_t report_map_data[] =
{
 0x06, 0x00, 0xFF, // Usage Page = 0xFF00 (Vendor Defined Page 1)
 0x09, 0x01, // Usage (Vendor Usage 1)
 0xA1, 0x01, // Collection (Application)
 0x19, 0x01, // Usage Minimum 
 0x29, INPUT_REPORT_MAX_LEN, // Usage Maximum 
 0x15, 0x00, // Logical Minimum (data bytes in the report may have minimum value = 0x00)
 0x26, 0xFF, 0x00, // Logical Maximum (data bytes in the report may have maximum value = 0x00FF = unsigned 255)
 0x75, 0x08, // Report Size: 8-bit field size
 0x95, INPUT_REPORT_MAX_LEN, // Report Count: Make sixty-four 8-bit fields (the next time the parser hits an "Input", "Output", or "Feature" item)
 0x81, 0x00, // Input (Data, Array, Abs): Instantiates input packet fields based on the above report size, count, logical min/max, and usage.
 0x19, 0x01, // Usage Minimum 
 0x29, OUTPUT_REPORT_MAX_LEN, // Usage Maximum
 0x91, 0x00, // Output (Data, Array, Abs): Instantiates output packet fields. Uses same report size and count as "Input" fields, since nothing new/different was specified to the parser since the "Input" item.
 0xC0 // End Collection
};
 
 And send your data like this: 
 err_code = ble_hids_inp_rep_send(&m_hids, 
 INPUT_REPORT_KEYS_INDEX,
 data_len,
 data);

nRF51422 HID example modification

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