I2C0 peripheral pins for my LPCXpresso 824 Max board.

[juliancox]

I am trying to attach an I2C peripheral to my LPCXpresso 824 Max board. The schematic from Embedded Artists shows SDA as PIO0_10, Pin 9 and SCL as PIO0_11, Pin  8 (both pins have pull-up resistors). However, file swm_8xx.h shows SDA as PIO0_11 and SCL as PIO0_12. Furthermore, the comment in one of the I2C example programs describes SDA as P0.10 and SCL as P0_11. Which are the correct ports and pins for I2C0?

[kerryzhou · Accepted solution]

Hi Julian,

Thank you for your interest in NXP LPC product, I would like to provide service for you!

1.LPCXpresso 824 Max board schematic I2C pin assignment

From the schematic:

http://cache.nxp.com/files/microcontrollers/hardware_tools/schematics/LPC824_Xpresso_v2_schematic_Re...

We can get that, I2C0_SCL is PIO10, I2C0_SDA is PIO11.

2. swm_8xx.h I2C defination

From the according lpcopen sample code, swm_8xx.h, we can get the I2C defination
    Chip_SWM_EnableFixedPin(SWM_FIXED_I2C0_SDA);
    Chip_SWM_EnableFixedPin(SWM_FIXED_I2C0_SCL);
STATIC INLINE void Chip_SWM_EnableFixedPin(CHIP_SWM_PIN_FIXED_T pin)
{
    LPC_SWM->PINENABLE0 &= ~((1 << (uint32_t) pin) | SWM_PINENABLE0_RESERVED);
}
#if defined(CHIP_LPC82X)
typedef enum CHIP_SWM_PIN_FIXED    {
    SWM_FIXED_ACMP_I1 = 0,    /*!< ACMP I1 */
    SWM_FIXED_ACMP_I2 = 1,    /*!< ACMP I2 */
    SWM_FIXED_ACMP_I3 = 2,    /*!< ACMP I3 */
    SWM_FIXED_ACMP_I4 = 3,    /*!< ACMP I4 */
    SWM_FIXED_SWCLK   = 4,    /*!< SWCLK */
    SWM_FIXED_SWDIO   = 5,    /*!< SWDIO */
    SWM_FIXED_XTALIN  = 6,    /*!< XTALIN */
    SWM_FIXED_XTALOUT = 7,    /*!< XTALOUT */
    SWM_FIXED_RST     = 8,    /*!< Reset */
    SWM_FIXED_CLKIN   = 9,    /*!< Clock Input */
    SWM_FIXED_VDDCMP  = 10,    /*!< VDD */
    SWM_FIXED_I2C0_SDA  = 11,    /*!< I2C0 SDA */
    SWM_FIXED_I2C0_SCL  = 12,    /*!< I2C0 SCL */
    SWM_FIXED_ADC0    = 13,    /*!< ADC0 */
    SWM_FIXED_ADC1    = 14,    /*!< ADC1 */
    SWM_FIXED_ADC2    = 15,    /*!< ADC2 */
    SWM_FIXED_ADC3    = 16,    /*!< ADC3 */
    SWM_FIXED_ADC4    = 17,    /*!< ADC4 */
    SWM_FIXED_ADC5    = 18,    /*!< ADC5 */
    SWM_FIXED_ADC6    = 19,    /*!< ADC6 */
    SWM_FIXED_ADC7    = 20,    /*!< ADC7 */
    SWM_FIXED_ADC8    = 21,    /*!< ADC8 */
    SWM_FIXED_ADC9    = 22,    /*!< ADC9 */
    SWM_FIXED_ADC10   = 23,    /*!< ADC10 */
    SWM_FIXED_ADC11   = 24,    /*!< ADC11 */
} CHIP_SWM_PIN_FIXED_T;

From the above code, you can get that, the swm_8xx.h is just define the I2C0 register LPC_SWM->PINENABLE0.

Please refer to user manual, page86, you will find:

SWN_PINENABLE 0[11]: enable I2C0_SDA on pin PIO0_11,

SWN_PINENABLE 0[12]: enable I2C0_SCL pin on  PIO0_10,

swm_8xx.h  just define the register, 11, 12 is just the PINENABLE0 regiser bit number, not pin number. The pin still PIO0_11,PIO0_10,

So the swm_8xx.h defination has no conflict with the schematic I2C pin assignment.

Wish it helps you!

If you still have question, please contact me!

Have a great day,
Jingjing

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[juliancox]

While trying to resolve this problem I examined the LPC824 pin descriptions in the NXP document UM10800 Table 402 on page 409 and it bears very little relation to "typedef enum CHIP_SWM_PIN_Fixed" in file "sim_8xx.h". If this is correct then very few of the fixed pin functions would ever work (which can't be true) !!!!!!!!