RTOS/AFE4404: How do I create a power on self test (POST) for the AFE4404?

Hi Roman,

One quick way is to disconnect the PD using "PD_DISCONNECT" bit and give input using Offset Cancellation DAC. The output should be,
Output = Offset DAC current * 2 * Rf.

Regards,
Prabin

Thank you!

I tried to implement your method but I'm having some difficulties.

Here's the code:

    set_up_afe4404();
    init_ti();
    apply_led_currents(0, 0, 0);

    reg_write(0x31, 0x000400);  // disable the photodiode
    reg_write(0x21, 0x000003);  // set the feedback resistor to 50 KOhms
    reg_write(0x3a, 0x000020);  // set the current offset to be 0.47 uA for LED1

    reg_write(0x00, 0x000001);
    uint32_t pd_disconnect = reg_read(0x31);
    uint32_t tia_gain = reg_read(0x21);
    uint32_t i_offset = reg_read(0x3a);
    reg_write(0x00, 0x000000);

    Task_sleep(1000000/Clock_tickPeriod);

//    reg_write(0x23, 0x000200);  // enable the internal osc

    while (1) {
        uint32_t led1val = reg_read(0x2c);

        double voltage = (led1val * 1.2) / 2097152;
        System_printf("ADC code: %x voltage: %f\n", led1val, voltage); System_flush();
        Task_sleep(2000/Clock_tickPeriod);
    }

I calculated that I should have 47 mV = (2) (50kohms) (0.47 uA)

but I keep getting:

ADC code: e3e4 voltage: 0.0333
ADC code: e3f9 voltage: 0.0333
ADC code: e402 voltage: 0.0333
ADC code: e36d voltage: 0.0333

The ADC codes keep changing and the number isn't what I calculated it to be.

Am I using the wrong approach?

Hi Roman,

I feel the difference between the calculated and measured value might be due to in accuracy of offset DAC and Rf.
Can you increase the Rf to 500KOhm and try once again?

Regards,
Prabin