nRF52840 TWI with EEPROM using registers directly

RE: nRF52840 TWI with EEPROM using registers directly

Nguyen Hoan Hoang — Wed, 25 Dec 2019 15:45:30 GMT

SES does not support C++ sorry. Can't be used with SES but you can use CrossWorks with external GCC compiler or IAR or Eclipse. See README.md of the repo

RE: nRF52840 TWI with EEPROM using registers directly

PoojaK — Wed, 25 Dec 2019 08:25:48 GMT

Hi,

I tried a lot but the .cpp file and project is not working in my ses.

And I am still stuck with my i2c.

I really need help 😞

RE: nRF52840 TWI with EEPROM using registers directly

Nguyen Hoan Hoang — Fri, 20 Dec 2019 13:31:28 GMT

This code here works with any Eeprom

https://github.com/IOsonata/IOsonata/blob/master/src/seep_impl.cpp

better i2c implementation here

https://github.com/IOsonata/IOsonata/blob/master/ARM/Nordic/src/i2c_nrf5x.cpp

RE: nRF52840 TWI with EEPROM using registers directly

PoojaK — Fri, 20 Dec 2019 12:58:41 GMT

I tried the code you have sent. I changed the code as per my device address and i2c pins.But I am not getting any data on the dso. Also as per the EEPROM I need to send Device address which is 8 bit then Start Address which is 16 bit and then the data to be transmitted.

So I made the following changes

void i2c_write(uint8_t addr, uint8_t data1)
{
  uint8_t tx_buf[3];
  NRF_TWIM0->SHORTS = TWIM_SHORTS_LASTTX_STOP_Msk;

  tx_buf[0] = 0x00 ; //(addr&&0x000000FF);
  tx_buf[1] = 0x01 ; //((addr&&0x0000FF00)>>8);
  tx_buf[2] = 0x55;

  NRF_TWIM0->TXD.MAXCNT = sizeof(tx_buf);
  NRF_TWIM0->TXD.PTR = (uint32_t)&tx_buf[0];

  NRF_TWIM0->EVENTS_STOPPED = 0;
  NRF_TWIM0->TASKS_STARTTX = 1;
  while (NRF_TWIM0->EVENTS_STOPPED == 0);
}

But I cannot see any data.

Also I tried writing my own routine in this manner which is working but the data sequence is getting mismatched

 while (1)
      {
        TimCnt = 0 ;
        NRF_TWI0->ADDRESS = 0x50 ;//(EEWriteAddress) ;//>>1) ; // EEWriteAddress ;
        NRF_TWI0->TXD = 0x55 ;//(u32startAddr & 0x000000FF);
        TimCnt = 0 ; 
        NRF_TWI0->EVENTS_STOPPED = 0 ; 
        NRF_TWI0->TASKS_STARTTX = 1 ;
        while((NRF_TWI0->EVENTS_TXDSENT) == 0)
        {
         
        }
        NRF_TWI0->TXD = 0x0f ;
        while((NRF_TWI0->EVENTS_TXDSENT) == 0)
        {
         
        }
        NRF_TWI0->TXD = 0x66 ;
        while((NRF_TWI0->EVENTS_TXDSENT) == 0)
        {
         
        }
        NRF_TWI0->TASKS_STOP = 1 ;
        while (NRF_TWI0->EVENTS_STOPPED == 0)
        {
        }
        TimCnt = 0 ; 
        while(TimCnt < 200) ;

As in I am getting Start Pulse->0x50->0x0F->0x66->0x55 as per the given code.

One more issue is that when I am sending the stop condition I am getting neither of the above.

Just Start->0x50->Stop

Please help me out here.

RE: nRF52840 TWI with EEPROM using registers directly

Hung Bui — Thu, 19 Dec 2019 15:01:16 GMT

I think you are doing it wrong. Please study the TWI peripheral in the datasheet. The address in NRF_TWI0->ADDRESS is not the address in the EEPROM you want to read, but it's the address of the EEPROM it self. It's the A0 A1 that you need to hardwire on your EEPROM (so it's either 0,1,2 or 3)

I attached here a bare metal code to do some read or write with a TWI address 0x2A:

#include <nrf.h>

#define DEVICE_ADDRESS   (0x2A)
#define PIN_SCL        (3)
#define PIN_SDA        (4)
uint8_t tx_buf[1];
uint8_t rx_buf[3];
 
void i2c_write(uint8_t addr, uint8_t data)
{
  uint8_t tx_buf[2];
  NRF_TWIM0->SHORTS = TWIM_SHORTS_LASTTX_STOP_Msk;

  tx_buf[0] = addr;
  tx_buf[1] = data;
  NRF_TWIM0->TXD.MAXCNT = sizeof(tx_buf);
  NRF_TWIM0->TXD.PTR = (uint32_t)&tx_buf[0];

  NRF_TWIM0->EVENTS_STOPPED = 0;
  NRF_TWIM0->TASKS_STARTTX = 1;
  while (NRF_TWIM0->EVENTS_STOPPED == 0);
}

void i2c_read(uint8_t addr)
{
  
  NRF_TWIM0->SHORTS = TWIM_SHORTS_LASTTX_STARTRX_Msk | TWIM_SHORTS_LASTRX_STOP_Msk;

  tx_buf[0] = addr;
  //tx_buf[1] = addr;
  NRF_TWIM0->TXD.MAXCNT = sizeof(tx_buf);
  NRF_TWIM0->TXD.PTR = (uint32_t)&tx_buf[0];

  NRF_TWIM0->RXD.MAXCNT = 1;
  NRF_TWIM0->RXD.PTR = (uint32_t)&rx_buf[0];

  NRF_TWIM0->EVENTS_STOPPED = 0;
  NRF_TWIM0->TASKS_STARTTX = 1;
  while (NRF_TWIM0->EVENTS_STOPPED == 0);

 // return rx_buf[0];
}
#include <stdint.h>
int main(void)
{
uint16_t i ,i1,i2;
  volatile uint8_t data;
 NRF_GPIO->PIN_CNF[PIN_SCL] = 
        (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos)
      | (GPIO_PIN_CNF_DRIVE_S0D1     << GPIO_PIN_CNF_DRIVE_Pos)
      | (GPIO_PIN_CNF_PULL_Pullup    << GPIO_PIN_CNF_PULL_Pos)
      | (GPIO_PIN_CNF_INPUT_Connect  << GPIO_PIN_CNF_INPUT_Pos)
      | (GPIO_PIN_CNF_DIR_Input      << GPIO_PIN_CNF_DIR_Pos);    
 NRF_GPIO->PIN_CNF[PIN_SDA] = 
        (GPIO_PIN_CNF_SENSE_Disabled << GPIO_PIN_CNF_SENSE_Pos)
      | (GPIO_PIN_CNF_DRIVE_S0D1     << GPIO_PIN_CNF_DRIVE_Pos)
      | (GPIO_PIN_CNF_PULL_Pullup    << GPIO_PIN_CNF_PULL_Pos)
      | (GPIO_PIN_CNF_INPUT_Connect  << GPIO_PIN_CNF_INPUT_Pos)
      | (GPIO_PIN_CNF_DIR_Input      << GPIO_PIN_CNF_DIR_Pos);    
      
  NRF_TWIM0->PSEL.SCL = PIN_SCL;
  NRF_TWIM0->PSEL.SDA = PIN_SDA;

  NRF_TWIM0->ADDRESS = DEVICE_ADDRESS;
  
  NRF_TWIM0->FREQUENCY = TWIM_FREQUENCY_FREQUENCY_K400 << TWIM_FREQUENCY_FREQUENCY_Pos;
  NRF_TWIM0->SHORTS = 0;
  NRF_TWIM0->ENABLE = TWIM_ENABLE_ENABLE_Enabled << TWIM_ENABLE_ENABLE_Pos;
 i2c_write(0x0, 0xFF);


  i2c_read(0x23);
 
  while (1)
  {
    __WFE();
  }
}

RE: nRF52840 TWI with EEPROM using registers directly

PoojaK — Thu, 19 Dec 2019 02:21:50 GMT

Hi Hung Bui,

I am not sending ACK or NACK in my code. I am just waiting for the slave to send a ACK pulse. The data sheet of AT24C512 says that once address has been transmitted we need to wait for the ACK bit and then continue further communication .

I will try the code

Thank you

RE: nRF52840 TWI with EEPROM using registers directly

Hung Bui — Wed, 18 Dec 2019 13:53:16 GMT

Hi PoojaK,

In your application you don't have to send ACK or NACK. It's handled by the TWI module itself.

Could you try to capture a logic analyzer trace of the communication ?

I would suggest you to have a look at this bare metal example here: https://github.com/andenore/NordicSnippets/tree/master/examples/i2c_master