[SOLVED] [Bare metal] H3 : Reading/Writing TWI registers

dmx512

I have the UART (other then the debug uart) and SPI working on bare metal.

However, I have an challenge with the TWI. Whatever I write to the TWI0 register, but it reads always 0 back.

The TWI_STAT register should read 0xF8.

I have set the proper GATING4 and RESET4 bit.

Any idea what I could be missing ?

Many thanks in advance, Arjan

1. void h3_i2c_begin(void) {
   
2.    h3_gpio_fsel(EXT_I2C_SCL, ALT_FUNCTION_SCK);
   
3.    h3_gpio_fsel(EXT_I2C_SDA, ALT_FUNCTION_SDA);
   
4. 
   
5. #if (EXT_I2C_NUMBER == 0)
   
6.    H3_CCU->BUS_SOFT_RESET4 |= RESET_TWI0;
   
7.    H3_CCU->BUS_CLK_GATING4 |= GATE_TWI0;
   
8. #elif (EXT_I2C_NUMBER == 1)
   
9.    H3_CCU->BUS_SOFT_RESET4 |= RESET_TWI1;
   
10.    H3_CCU->BUS_CLK_GATING4 |= GATE_TWI1;
    
11. #else
    
12. #error Unsupported I2C device configured
    
13. #endif
    
14. 
    
15.    _soft_reset();
    
16. 
    
17. #ifndef NDEBUG
    
18.    printf("H3_PIO_PORTA->CFG1=%p\n", H3_PIO_PORTA->CFG1);
    
19.    print_bits(H3_PIO_PORTA->CFG1);
    
20.    printf("H3_CCU->BUS_CLK_GATING4=%p\n", H3_CCU->BUS_CLK_GATING4);
    
21.    printf("H3_CCU->BUS_SOFT_RESET4=%p\n", H3_CCU->BUS_SOFT_RESET4);
    
22.    printf("EXT_I2C=%p\n", EXT_I2C);
    
23.    printf("EXT_I2C_SCL=%d\n", EXT_I2C_SCL);
    
24.    printf("EXT_I2C_SDA=%d\n", EXT_I2C_SDA);
    
25.    printf("EXT_I2C->STAT=%p [%p]\n", EXT_I2C->STAT, &EXT_I2C->STAT);
    
26.    printf("EXT_I2C->SRST=%p [%p]\n", EXT_I2C->SRST, &EXT_I2C->SRST);
    
27.    printf("EXT_I2C->LCR=%p [%p]\n", EXT_I2C->LCR, &EXT_I2C->LCR);
    
28. #endif
    
29. }
    
30. 
    
31. static inline void _soft_reset(void) {
    
32.    uint32_t value = EXT_I2C->SRST;
    
33.    value |= TWI_SRST_SRST;
    
34.    EXT_I2C->SRST = value;
    
35. 
    
36.    uint16_t timeout = 0xFFFF;
    
37. 
    
38.    while (((EXT_I2C->SRST & TWI_SRST_SRST) == TWI_SRST_SRST) && (timeout-- > 0))
    
39.       ;
    
40. 
    
41. #ifndef NDEBUG
    
42.    printf("_soft_reset - timeout=%d\n", timeout);
    
43. #endif
    
44. }

Copy code

1. --> src/h3_i2c.c:h3_i2c_begin:742
   
2. h3_gpio_fsel gpio=11, port=0[A], number=11, reg=1, shift=12, pio=0x01c20800
   
3. h3_gpio_fsel gpio=12, port=0[A], number=12, reg=1, shift=16, pio=0x01c20800
   
4. _soft_reset - timeout=65535
   
5. H3_PIO_PORTA->CFG1=0x77722777
   
6. 0  1  2  4  5  6  8  9  10 13 17 20 21 22 24 25 26 28 29 30
   
7. H3_CCU->BUS_CLK_GATING4=0x00000001
   
8. H3_CCU->BUS_SOFT_RESET4=0x00010001
   
9. EXT_I2C=0x01c2ac00
   
10. EXT_I2C_SCL=11
    
11. EXT_I2C_SDA=12
    
12. EXT_I2C->STAT=0x00000000 [0x01c2ac10]
    
13. EXT_I2C->SRST=0x00000000 [0x01c2ac18]
    
14. EXT_I2C->LCR=0x00000000 [0x01c2ac20]
    
15. <-- src/h3_i2c.c:h3_i2c_begin:772

Copy code

dmx512

I had the Gating wrong

1. void h3_i2c_begin(void) {
   
2.         h3_gpio_fsel(EXT_I2C_SCL, ALT_FUNCTION_SCK);
   
3.         h3_gpio_fsel(EXT_I2C_SDA, ALT_FUNCTION_SDA);
   
4. 
   
5. #if (EXT_I2C_NUMBER == 0)
   
6.         H3_CCU->BUS_SOFT_RESET4 |= RESET_TWI0;
   
7.         H3_CCU->BUS_CLK_GATING3 |= GATE_TWI0;
   
8. #elif (EXT_I2C_NUMBER == 1)
   
9.         H3_CCU->BUS_SOFT_RESET4 |= RESET_TWI1;
   
10.         H3_CCU->BUS_CLK_GATING3 |= GATE_TWI1;
    
11. #else
    
12. #error Unsupported I2C device configured
    
13. #endif

Copy code