No readings from LSM9DS1 using TWI example

RE: No readings from LSM9DS1 using TWI example

hmolesworth — Tue, 18 Aug 2020 17:49:28 GMT

Looks good, thanks for the feedback. Cheers

RE: No readings from LSM9DS1 using TWI example

drewvigne — Tue, 18 Aug 2020 16:59:44 GMT

They sell two nRF52840 variants:

Arduino Nano 33 BLE - has only the LSM9DS1 (I'm using this one)
Arduino Nano 33 BLE Sense - has an array of sensors including the LPS22 and LSM9DS1

My GitHub repo, Arduino_Nano_33_ANT, may be of use to you if you go down this path. Contains the board def, some compatible examples, etc.

RE: No readings from LSM9DS1 using TWI example

hmolesworth — Tue, 18 Aug 2020 16:14:41 GMT

Nice! Looking at the circuit there is an LPS22 pressure sensor, but the doc doesn't seem to mention it .. is it fitted to the board? That's a nice board, I've been using the Feather boards for development but might try this ..

RE: No readings from LSM9DS1 using TWI example

drewvigne — Tue, 18 Aug 2020 16:04:19 GMT

Brilliant. Just created a function to do that and added it to main. Detects the I2C sensor addresses flawlessly. Cheers.

RE: No readings from LSM9DS1 using TWI example

hmolesworth — Tue, 18 Aug 2020 15:55:17 GMT

Quite so, I assumed you already had those set; ensure they are both high-drive (S0H1), 2 x 4k7 is quite a load but it will work:

#define  PIN_VDD_ENV    (22)
#define  PIN_R_PULLUP   ( 0+32)

  nrf_gpio_pin_set(PIN_VDD_ENV);
  nrf_gpio_pin_set(PIN_R_PULLUP);
  // Power up and wait for voltage to rise
  nrf_gpio_cfg(PIN_VDD_ENV,  NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_DISCONNECT, NRF_GPIO_PIN_NOPULL, NRF_GPIO_PIN_S0H1, NRF_GPIO_PIN_NOSENSE);
  nrf_gpio_cfg(PIN_R_PULLUP, NRF_GPIO_PIN_DIR_OUTPUT, NRF_GPIO_PIN_INPUT_DISCONNECT, NRF_GPIO_PIN_NOPULL, NRF_GPIO_PIN_S0H1, NRF_GPIO_PIN_NOSENSE);
  nrf_delay_ms(4);

I see at least 4u7 capacitance, so you might have to extend the 4mSec delay to allow that to charge, maybe 10mSec

RE: No readings from LSM9DS1 using TWI example

drewvigne — Tue, 18 Aug 2020 15:29:32 GMT

Tried this and unfortunately it did not work. Could it be my board definition? The Arduino has VDD_ENV and R_PULLUP mappings so I wonder if there is a function in NRF_GPIO that handles this.

RE: No readings from LSM9DS1 using TWI example

hmolesworth — Tue, 18 Aug 2020 15:15:37 GMT

Pull-ups are 4k7, which is fine for 100KHz but with multiple devices the nRF52 will struggle to get good low-level drive on the settings you are using. Try switching to H0D1 (High Drive '0', Disconnect Drive '1') thus:

void twi_init (void)
{
    ret_code_t err_code;
    const nrf_drv_twi_config_t twi_config = {
       .scl                = ARDUINO_SCL1_PIN,
       .sda                = ARDUINO_SDA1_PIN,
       .frequency          = NRF_DRV_TWI_FREQ_100K,
       .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
       .clear_bus_init     = false
    };
    err_code = nrf_drv_twi_init(&m_twi, &twi_config, NULL, NULL);
    APP_ERROR_CHECK(err_code);
    nrf_drv_twi_enable(&m_twi);
    // To secure correct signal levels on the pins used by the TWI master when the system is in OFF mode, and
    // when the TWI master is disabled, SDA and SCL pins must be configured in the GPIO peripheral as follows:
    // SCL As specified in PSEL.SCL: Input H0D1
    // SDA As specified in PSEL.SDA: Input H0D1
    nrf_gpio_cfg(ARDUINO_SDA1_PIN, NRF_GPIO_PIN_DIR_INPUT, NRF_GPIO_PIN_INPUT_CONNECT, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_H0D1, NRF_GPIO_PIN_NOSENSE);
    nrf_gpio_cfg(ARDUINO_SCL1_PIN, NRF_GPIO_PIN_DIR_INPUT, NRF_GPIO_PIN_INPUT_CONNECT, NRF_GPIO_PIN_PULLUP, NRF_GPIO_PIN_H0D1, NRF_GPIO_PIN_NOSENSE);
}

RE: No readings from LSM9DS1 using TWI example

drewvigne — Tue, 18 Aug 2020 14:48:34 GMT

Here is the schematic I'm dealing with. We have a VDD, SDA1, SCL1, and of course ground connections being made. Arduino did a silly thing not to include the interrupt pin but that's a different issue.

I'm testing with only the unmodified scanner example now. Unable to communicate with the slave whatsoever. Debugging currently but still unsure of the issue. I wonder if it has to do with a pullup.

RE: No readings from LSM9DS1 using TWI example

Einar Thorsrud — Tue, 18 Aug 2020 13:00:11 GMT

Hi,

[quote user=""]Note: Also working with the TWI scanner example. Same issue here... getting stuck in the device id portion of the code.[/quote]

It is not clear to me whether you are able to communicate with the slave device at all. Are you? What happens if you use an unmodified TWI scanner example? Is the slave found? If not, we need to look at that first, so make sure the basics are in place.