Unable to Read or write MMA8652 registers using TWI

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Thu, 27 Apr 2017 13:40:20 GMT

Yes, the twi_master driver is deprecated in favor of the new nrf_drv_twi.c driver. Unfortunately, I do not have a MMA8652 that I can test against. I modified the twi_sensor example in SDK v11.0.0 so that its more inline with the snippets I've put in the comments. It first does a nrf_drv_twi_tx to tell the MMA7660 which register it should read from, in this case MMA7660_REG_XOUT. Then it reads 3 bytes which is MMA7660_REG_XOUT, MMA7660_REG_YOUT and MMA7660_REG_ZOUT and prints it to the uart. Here is the main file: main.c

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Wed, 26 Apr 2017 14:40:33 GMT

but in SDK it is showing that twi_master is deprecated.

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Wed, 26 Apr 2017 14:39:40 GMT

yes but it is not working. so that i am using twi_master example it is working fine and i able to read and write to the registers.

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Wed, 26 Apr 2017 12:37:15 GMT

@saiteja: Did you try my suggestions?

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Sat, 22 Apr 2017 13:16:35 GMT

drive.google.com/open

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Fri, 21 Apr 2017 12:23:35 GMT

Ok, try reading other registers and see if you get any thing other than zeroes. If you still get zeroes and you are sure that the addresses are correct, then the only thing I can suggest is that you need to check if the connections are correct.

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Fri, 21 Apr 2017 12:20:40 GMT

i do not have logic analyzer

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Fri, 21 Apr 2017 12:16:38 GMT

Atleast the TWI operations are returning NRF_SUCCESS. Can you verify that you're writing to the correct register? Do you have a logic analyzer or similar so that you can perform a logic trace?

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Fri, 21 Apr 2017 12:08:57 GMT

hi i have tried with that, it is showing NRF_SUCCESS on both TX andRX operation. but i am getting empty value on reg_read buffer.

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Fri, 21 Apr 2017 09:31:19 GMT

Could you try to just set the m_xfer_done flag in the twi handler and nothing else, i.e.

case NRF_DRV_TWI_EVT_DONE:
    //string_send("1twirxsuc\r\n");
    if ((p_event->type == NRF_DRV_TWI_EVT_DONE) &&
            (p_event->xfer_desc.type == NRF_DRV_TWI_XFER_TX))
    {
        if(m_set_mode_done != true)
        {
            m_set_mode_done  = true;
            return;
        }
        m_xfer_done = true;
    }

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Fri, 21 Apr 2017 07:56:44 GMT

updated my Question? with twi_event_handler function, please find it. EDIT:--

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Fri, 21 Apr 2017 07:13:15 GMT

I afraid that we do not have any example for communicating with the MMA8652FC. Can you post the twi_event_handler function?

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Fri, 21 Apr 2017 05:33:30 GMT

i have one doubt if i want to read data from register i need to TX register address and Then i need to read. here my MMA8652_I2C_ADDR is 0X1D but in the mma8652 documentation, it is saying that use 0X3A for tx and 0X3B for rx operation. but i am unable to get register data even if done both methods. and also i am getting NRF_SUCCESS return code. i s there any simple application to just read and write from MMA8652FC. thank you. and also did i need to put the MMA8652 in standby and Active for both tx and rx operations.

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Thu, 20 Apr 2017 16:54:03 GMT

i am getting NRF_SUCCESS after nrf_drv_twi_tx but now i am getting NRF_BUSY for nrf_drv_twi_rx.

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Thu, 20 Apr 2017 08:37:40 GMT

If you take a look at the documentation of nrf_drv_twi_tx you'll see that nrf_drv_twi_tx returns NRF_ERROR_BUSY if there is a transfer on going. Like the TWI sensor example you have to wait for the previous transfer to finish by waiting for the m_xfer_done to be set in the twi event handler, i.e.

while(m_xfer_done == false);
err_code=nrf_drv_twi_tx(&m_twi_mma_8652, MMA8652_I2C_ADDR, &W_reg, sizeof(W_reg), false);
APP_ERROR_CHECK(err_code);
m_xfer_done = false;

while(m_xfer_done == false);
err_code = nrf_drv_twi_rx(&m_twi_mma_8652, MMA8652_I2C_ADDR, &W_reg, sizeof(W_reg));
APP_ERROR_CHECK(err_code);
m_xfer_done = false;

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Thu, 20 Apr 2017 05:31:21 GMT

Hi, the error code is NRF_ERROR_BUSY

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Wed, 19 Apr 2017 14:43:13 GMT

Does nrf_drv_twi_tx return an error code? I do not understand what you mean by "is salve address for all MMA8652FC is 0X1D?"

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Wed, 19 Apr 2017 12:50:07 GMT

is salve address for all MMA8652FC is 0X1D?

RE: Unable to Read or write MMA8652 registers using TWI

saiteja — Wed, 19 Apr 2017 12:49:18 GMT

the code stuck at nrf_drv_twi_tx

RE: Unable to Read or write MMA8652 registers using TWI

bjorn-spockeli — Wed, 19 Apr 2017 12:46:58 GMT

In the first code snippet, where does the program get "stuck"? Does nrf_drv_twi_tx or nrf_drv_twi_rx return an error code? If you do not tell the MMA8652 from which register address you're going to read from by performing a nrf_drv_twi_tx() before nrf_drv_twi_rx, then it will just start reading from register 0x00. If you take a look in the MMA8652 Datasheet, found here, you'll see that the OUT_X_MSB data starts from 0x01 and not 0x00 like the MMA7660. Register 0x00 is default set to 0x00 in the MMA8652, so thats probably why the x value stays zero. Thus, the first method is the better choice.