(nrf51822-EK) How to read twi Multiple Byte ?

[aworks]

Hi.

My board : nrf51822 -Evaluation Kit ------ mma8452q problem : read_registers(MMA8452_ADDRESS << 1,OUT_X_MSB, 6, rawData); source code : link text

main.c -> readAccelData-> read_registers -> twi_master_transfer(device_address | TWI_READ_BIT, value, size, TWI_ISSUE_STOP);

I can read Single Byte. I can write Single Byte.

But I can't read Multiple Byte.

How to read Multiple Byte?

Could you give me some tips? How to solve this problem..?

[Stian Røed Hafskjold]

The twi_master_transfer() function you refer to is a part of the TWI peripheral driver and is documented here: developer.nordicsemi.com/.../a00769.html

Here you can see that it takes an argument, data_length, which specifies how many bytes that should be transferred from the data array.

In the twi_master_transfer() function (in twi_sw_master.c) you can see that it will not continue to clock out bytes if twi_master_clock_byte() returns false. This function returns false if it does not receive an ACK bit from the slave:

// Read ACK/NACK. NACK == 1, ACK == 0
transfer_succeeded &= !(TWI_SDA_READ());

You should have a logic analyzer in order to be able to debug the TWI bus.

[aworks]

I solved this problem. Thank you