Creating a load on a battery using the radio

RE: Creating a load on a battery using the radio

hmolesworth — Wed, 02 Oct 2024 22:37:21 GMT

Excellent suggestion. There is no +8dBm option on the nrf52832 (which I ran this test on) and I see these results @3V on nRF52832 with cpu awake, no DC-DC, no hardware attached to io pins and no peripherals enabled.

23mA at +4dBm is most useful for a faster battery test.

  NRF_RADIO->TXPOWER = 0x08; // +8dBm 11.35mA
  NRF_RADIO->TXPOWER = 0x04; // +4dBm 23.17mA
  NRF_RADIO->TXPOWER = 0x00; //  0dBm 17.42mA

RE: Creating a load on a battery using the radio

JZone — Wed, 02 Oct 2024 20:02:10 GMT

Thanks for the suggestions. The following solution seems to work

NRF_RADIO->MODE = 0; // 1 Mbps Nordic proprietary radio mode
NRF_RADIO->TXPOWER = 0x08; // +8dBm
NRF_RADIO->TASKS_TXEN = 1;

test_battery();

NRF_RADIO->TXPOWER = 0; // Set back to default

NRF_RADIO->TASKS_DISABLE = 1;

RE: Creating a load on a battery using the radio

hmolesworth — Thu, 26 Sep 2024 23:54:46 GMT

Continuous Rx until advertising packet received (then restart Rx) with HFCLK crystal enabled I see 8.8mA @3V on nRF52832 with no DC-DC, no hardware attached to io pins and no peripherals enabled.

RE: Creating a load on a battery using the radio

hmolesworth — Thu, 26 Sep 2024 16:31:39 GMT

I do something similar for measuring coin cell capacity by monitoring voltage decay under a known load via Bare-metal Radio Transmit. Similar to solar_sensor_beacon sample on the Nordic GitHub repo. The code can be run before nRFConnect stuff if using nRFConnect environment.

solar_sensor_beacon

advertising-using-raw-radio-registers

Edit: I wrote these notes, might be useful if you want to actually have detectable advertising packets. Note also that you can get a fixed load by using Rx instead of Tx if you want to keep the environment cleaner.

// BLE Advertising Packet
// ======================
// Every packet begins with an 8 bit preamble, an alternating binary sequence. This is followed by a 32 bit access
// address (AA) which can be thought of as a unique identifier which defines a particular connection. When a
// device (master or slave) transmits on an advertising channel it uses a fixed value of 0x8e89bed6 as the access
// address.
// Following the 32 bit access address are optional S0, LENGTH and S1 fields then a variable length Protocol Data
// Unit (PDU) which contains the message data payload. Finally all packets end with a 24 bit CRC.
// By default, the Nordic BLE address is derived from the NRF_FICR->DEVICEADDR[] and is 48 bits in length (6 bytes)
// If S0, LENGTH or S1 are specified with zero length their fields will be omitted in memory, otherwise each
// field will be represented as a separate byte, regardless of the number of bits in their on-air counterpart
// For the field sizes defined in bits, the occupation in RAM will always be rounded up to the next full byte size
// (for instance 3 bit length will allocate 1 byte in RAM, 9 bit length will allocate 2 bytes, etc.).
// On-air packet layout (Note Header in RAM is 3 bytes if S0INC is '1')
// +-------------------------------------------------------------------------------------------------------------------------+
// |                                         BLE Advertising Packet - Legacy                                                 |
// +-------------------------------------------------------------------------------------------------------------------------+
// |                                         1MHz: 47 octets max total length                                                |
// +--------+-------+------------------------------------------------------------------------------------------+------+------+
// |        |Access |                                                                                          | Add  |      |
// |Preamble|Address|                   Protocol Data Unit PDU                                                 | On   | CRCC | Tone Ext
// +--------+-------+------------------------------------------------------------------------------------------+------+------+
// |   1(2) |   4   |                                    2 - 39                                                | (0)  |  3   | 16 - 160uSec
// |        |       +-----------------+------------------------------------------------------------------------+      |      |
// |        |       |    Header       |                  Payload                                               |      |      |
// |        |       +-----------------+------------------------------------------------------------------------+      |      |
// |        |       |       2         |                  0 - 37                                                |      |      |
// |        |       +-----+-----+-----+------------------------------------------------------------------------+      |      |
// |        |       | Opt | Opt | Opt |  MAC Addr  |     AdvData List (example 3 fields)                       |      |      |
// |        |       | S0  | Len | S1  +------------+-----------------------------------------------------------+      |      |
// |        |       |-----+-----+-----|    6       |     0 - 31                                                |      |      |
// |        |       | (1) | (1) | (1) |            +-------------------+-------------------+-------------------+      |      |
// |        |       |     |     |     |            |    AdvData Flags  |    AdvData Name   |   (AdvData Data)  |      |      |
// |        |       |     |     |     |            +-------------------+-------------------+-------------------+      |      |
// |        |       |     |     |     |            |        3          |          6        |       0 - 22      |      |      |
// |        |       |     |     |     |            +-----+------+------+-----+------+------+-----+------+------+      |      |
// |        |       |     |     |     |            | Len | Type | Data | Len | Type | Data | Len | Type | Data |      |      |
// |        |       |     |     |     |            +-----+------+------+-----+------+------+-----+------+------+      |      |
// |        |       |     |     |     |            |  1  |  1   |  1   |  1  |  1   |  4   |  1  |  1   |  20  |      |      |
// |        |       |     |     |     |            |     |      |      |     |      |      |     |      |      |      |      |
// |  1(2)  |  4    | (1) | (1) | (1) |   6        |  1  |  1   |  1   |  1  |  1   |  4   |  1  |  1   |  20  | (0)  |  3   |
// +--------+-------+-----+-----+-----+------------+-----+------+------+-----+------+------+-----+------+------+------+------+
//         0x8E89BED6     |     |      \
//                /       |     |       \
//               /  RAM uses 2+ bytes    \
//              / 1 byte | 2 bit | 6 bit  \
//             /                           \
//            /  OTA only 2 bytes for BLE   \
//           |                         |     |
//           Type RFU ChSet TxAdd RxAdd Length
//    bits:    4   1    1     1     1     8

RE: Creating a load on a battery using the radio

JZone — Thu, 26 Sep 2024 16:10:45 GMT

The test is intended too be executed only during a power-on of the normal application

1. Normal application starts

2. Put radio in TX by a direct configuration of radio registers

3. Measure battery voltage for 1 to 2s

4. Disable radio

4. If battery ok, continue with initialization of the app, start the Soft Device.......

RE: Creating a load on a battery using the radio

Sigurd — Thu, 26 Sep 2024 08:29:45 GMT

Hi!

Then putting the radio in TX is likely the option.

Could you elaborate on how this should work in practice?

Would it be something used in your normal application hex?

Would it be some test-mode you put the chip into, instead of booting the normal application?

Or something that you would need to do every x amount of time while running the normal application?

RE: Creating a load on a battery using the radio

JZone — Wed, 25 Sep 2024 16:30:10 GMT

Thanks for the response. I need more than that. 10 to 20mA would be ideal.

RE: Creating a load on a battery using the radio

Sigurd — Wed, 25 Sep 2024 09:31:07 GMT

Hi!

What level of load is needed? if ~3mA is okay, then the easiest is just to let the CPU run, and not put it into idle mode.

Snippet:

While(true)

{

__NOP();

}

https://docs.nordicsemi.com/bundle/ps_nrf52833/page/_tmp/nrf52833/autodita/CURRENT/parameters.i_cpu.html