I2C master-slave communication problem

[ast8346]

Posted on December 20, 2016 at 13:35

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[waclawek.jan]

Posted on December 20, 2016 at 14:22

Receiver does not work.

Make sure your connections are OK. Read back the GPIO registers in a debugger and verify their content is what you intended.

[EDIT]  

I2C_CR2:

SADD[7:1]: Slave address bit 7:1 (master mode)

In 7-bit addressing mode (ADD10 = 0):

These bits should be written with the 7-bit slave address to be sent

I2C_OAR1:

Bits 7:1 OA1[7:1]: Interface address

Bits 7:1 of address

Well, the latter is just another incarnation of the 'I don't understand the 7-bit address from I2C specification'. OA1 should contain the 7-bit address, ergo, drop the shift in

 I2C1->OAR1 |= (0x10<<1); // set own address

JW

PS.

 

[ast8346]

Posted on December 20, 2016 at 15:48

Right, so the address value has to be in the range between 0x08 and 0x77

Also, the I2C_write function should have address shifted to the left once as well as the bit 0 has to do with 10-bit interface

I2C1->CR2 = I2C_CR2_RELOAD | (uint32_t) (1 << 16) | (uint32_t) (address << 1);

I have changed that, but my code still does not work

:(

[waclawek.jan]

Posted on December 20, 2016 at 16:53

The address both in OAR and CR2 has the same structure, so either shift both (treating them as 7-bit address as per I2C spec) or none (treating them as the 'customary' 8-bit address).

If you have both shifted, then again, double-check the connections and the macros you've used in the slave code.

JW