BLE Central tutorial not connecting to my peripheral

RE: BLE Central tutorial not connecting to my peripheral

Bret Foreman — Wed, 02 Dec 2015 19:45:24 GMT

I've been working from the BLE Central tutorial all along. The documentation is pretty incomplete and most of the comments in the code are not very helpful. It's been slow going. For example, it's not clear at all what's going on with cccd_configure function or how the arguments sent to it by ble_uart_c_rx_notif_enable work.

RE: BLE Central tutorial not connecting to my peripheral

Anders Strand — Wed, 02 Dec 2015 10:06:32 GMT

The BLE central tutorial could be a good starting place.

RE: BLE Central tutorial not connecting to my peripheral

Bret Foreman — Tue, 01 Dec 2015 19:56:30 GMT

I got the the advertising to work and it's connecting to my BLE Central. Now I'm working on getting the service discovery to work on the Central side. I can see my service in the Android MCP, but not on the Central. I'll start a new thread for this issue.

RE: BLE Central tutorial not connecting to my peripheral

Anders Strand — Tue, 01 Dec 2015 12:03:22 GMT

Hi.

I will start by explaining a couple of concepts regarding UUID's and advertising. Then i will address your errors.

When dealing with 128 bits UUID's, we use a base uuid (128 bit) and a service uuid (16 bit). For example in advertising, the 16 bit uuid is places on byte 12 and 13 of the base uuid, and advertised.

This is copied from the UUID section of the BLE services tutorial:

"The second type is a 128-bit UUID, sometimes referred to as a vendor specific UUID. 
This is the type of UUID you need to use when you are making your own custom services and characteristics. 
It looks something like this: 4A98xxxx-1CC4-E7C1-C757-F1267DD021E8 and is called the “base UUID”. 
The four x’s represent a field where you will insert your own 16-bit IDs for your custom services and characteristics and use them just like a predefined UUID. 
This way you can store the base UUID once in memory, forget about it, and work with 16-bit IDs as normal."

In the nus (Nordic Uart Service) example we use the function

sd_ble_uuid_vs_add(&nus_base_uuid, &p_nus->uuid_type)

to add a base uuid to the softdevice. The p_nus->uuid_type will be written when calling the function. This variable will contain the uuid type of the base uuid. In practice, it is a number to where in a table the base uuid was stored.

The first time we call sd_ble_uuid_vs_add, the base uuid we put in is stored at the index BLE_UUID_TYPE_VENDOR_BEGIN. Therefore. If we add another, it will be at BLE_UUID_TYPE_VENDOR_BEGIN+1. Since you are only using one custom service (i am assuming), your base uuid will be at BLE_UUID_TYPE_VENDOR_BEGIN.

In any case: The best way to do this is to store the value p_nus->uuid_type, and use this whenever we do anything related to the base uuid. (For example adding a service, or adding the full uuid to the advertising packet). We can see that this is actually being done by the NUS code inside ble_nus_init.

Now. In the NUS peripheral example, we see that the type BLE_UUID_TYPE_VENDOR_BEGIN is used for the type in the uuid array m_adv_uuids. This is actually a "shortcut" or easy solution. Since we know that we will only add one custom (or vendor specific) uuid, we know that BLE_UUID_TYPE_VENDOR_BEGIN will be the correct type.

On to solving your issue. Either use BLE_UUID_TYPE_VENDOR_BEGIN as the uuid type THROUGHPUT_SERVICE_UUID_TYPE. Or use the uuid type stored in m_nus.uuid_type.

Let me know if anything is unclear.

-Anders

RE: BLE Central tutorial not connecting to my peripheral

Bret Foreman — Tue, 01 Dec 2015 01:11:25 GMT

One more detail, my UUID type is calculated like this:

#define THROUGHPUT_SERVICE_UUID_TYPE (BLE_UUID_TYPE_VENDOR_BEGIN + 1)

RE: BLE Central tutorial not connecting to my peripheral

Bret Foreman — Tue, 01 Dec 2015 01:07:07 GMT

Ah, I see what's wrong. My short and long UUIDs don't match. I fixed that and now I'm getting an invalid parameter error from ble_advertising_init. Tracing into it makes me think the problem is in the second argument, the scan response. I'm setting up the second argument like this:

scanrsp.uuids_complete.uuid_cnt = 1;
scanrsp.uuids_complete.p_uuids  = throughput_short_uuid_list;
err_code = ble_advertising_init(&advdata, &scanrsp, &options, on_adv_evt, NULL);

Where throughput_short_uuid_list is defined like this:

static ble_uuid_t throughput_short_uuid_list[] = {{ .uuid = 0 , .type = THROUGHPUT_SERVICE_UUID_TYPE }};

Is this the correct way to call the function with this parameter?

RE: BLE Central tutorial not connecting to my peripheral

Bret Foreman — Mon, 30 Nov 2015 22:32:00 GMT

I should clarify that both the S130 Central and the MCP are seeing the same UUID, with position 12 changed from what I'm trying to send from the Peripheral.

RE: BLE Central tutorial not connecting to my peripheral

Bret Foreman — Mon, 30 Nov 2015 22:28:32 GMT

I found a problem, though it does not point to any obvious root cause. The peripheral is sending UUID: 0x9E, 0xCA, 0xDC, 0x24, 0x0E, 0xE5, 0xA9, 0xE0, 0x93, 0xF3, 0xA3, 0xB5, 0x00, 0x00, 0x40, 0x6E. But the Central is receiving UUID: 0x9E, 0xCA, 0xDC, 0x24, 0x0E, 0xE5, 0xA9, 0xE0, 0x93, 0xF3, 0xA3, 0xB5, 0x01, 0x00, 0x40, 0x6E.

Note that position 12 (counting from 0) is a 0x01 at the Central rather than the 0x00 sent by the peripheral.

Any ideas why this might be happening?

RE: BLE Central tutorial not connecting to my peripheral

Anders Strand — Thu, 26 Nov 2015 08:53:54 GMT

Can you post a screenshot of the advertisement data shown in MCP? optionally, write all the uuid's in the advertisement packet here.