Sampling data with 4 ADC channels on NRF52 (BL654 module)

Question

Hello, 
 I'm using BL654 module (nrf52840 inside); SDK15; softdevice s140; IAR. 
 In my projects I'm using peripherals: I2C(TWI), SPI. Project based on ble_app_uart example (most of sdk_config.h are default, exept TWI/SPI instances and timer3) 
 My goal is to add sampling data from 4 analog input channels:

Channel 1 - input 0; 
 Channel 2 - input 5; 
 Channel 3 - input 4; 
 Channel 4 - input 7; 
 
 My code for SAADC: 
 #define SAMPLES_IN_BUFFER 4
#define BUFFERS_IN_CH 2
#define SAADC_SAMPLE_PERIOR_MS 1000
volatile uint8_t state = 1;


static const nrf_drv_timer_t m_timer = NRF_DRV_TIMER_INSTANCE(3);
static nrf_saadc_value_t m_buffer_pool[BUFFERS_IN_CH][SAMPLES_IN_BUFFER];
static nrf_ppi_channel_t m_ppi_channel;
static uint32_t m_adc_evt_counter;


void timer_handler(nrf_timer_event_t event_type, void * p_context)
{
 //
}


void saadc_sampling_event_init(void)
{
 ret_code_t err_code;

 err_code = nrf_drv_ppi_init();
 APP_ERROR_CHECK(err_code);

 nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
 timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_32;
 err_code = nrf_drv_timer_init(&m_timer, &timer_cfg, timer_handler);
 APP_ERROR_CHECK(err_code);

 // setup m_timer for compare event every X ms
 uint32_t ticks = nrf_drv_timer_ms_to_ticks(&m_timer, SAADC_SAMPLE_PERIOR_MS);
 nrf_drv_timer_extended_compare(&m_timer,
 NRF_TIMER_CC_CHANNEL3,
 ticks,
 NRF_TIMER_SHORT_COMPARE3_CLEAR_MASK,
 false);
 nrf_drv_timer_enable(&m_timer);

 uint32_t timer_compare_event_addr = nrf_drv_timer_compare_event_address_get(&m_timer,
 NRF_TIMER_CC_CHANNEL3);
 uint32_t saadc_sample_task_addr = nrf_drv_saadc_sample_task_get();

 // setup ppi channel so that timer compare event is triggering sample task in SAADC
 err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
 APP_ERROR_CHECK(err_code);

 err_code = nrf_drv_ppi_channel_assign(m_ppi_channel,
 timer_compare_event_addr,
 saadc_sample_task_addr);
 APP_ERROR_CHECK(err_code);
}

void saadc_sampling_event_enable(void)
{
 ret_code_t err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);
 APP_ERROR_CHECK(err_code);
}

void saadc_callback(nrf_drv_saadc_evt_t const * p_event)
{
 if (p_event->type == NRF_DRV_SAADC_EVT_DONE)
 {
 ret_code_t err_code;
 
 // set buffers
 err_code = nrf_drv_saadc_buffer_convert(p_event->data.done.p_buffer, SAMPLES_IN_BUFFER);
 APP_ERROR_CHECK(err_code);
 
 // print samples on hardware UART and parse data for BLE transmission
 NRF_LOG_INFO("ADC event number: %d
",(int)m_adc_evt_counter);
 for (int i = 0; i < SAMPLES_IN_BUFFER; i++)
 {
 NRF_LOG_INFO("CH_[%d] adc_value: %d
", i, p_event->data.done.p_buffer[i]);
 } 
 m_adc_evt_counter++;
 }
}

void saadc_init(void)
{
 ret_code_t err_code;
	
 nrf_drv_saadc_config_t saadc_config = NRF_DRV_SAADC_DEFAULT_CONFIG;
 saadc_config.resolution = NRF_SAADC_RESOLUTION_12BIT;
	
 nrf_saadc_channel_config_t channel_1_config =
 NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN0);
	
 nrf_saadc_channel_config_t channel_2_config =
 NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN5);
	
 nrf_saadc_channel_config_t channel_3_config =
 NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN4);
	
 nrf_saadc_channel_config_t channel_4_config =
 NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN7); 
	
 err_code = nrf_drv_saadc_init(&saadc_config, saadc_callback);
 APP_ERROR_CHECK(err_code);

 err_code = nrf_drv_saadc_channel_init(0, &channel_1_config);
 APP_ERROR_CHECK(err_code);
 err_code = nrf_drv_saadc_channel_init(5, &channel_2_config);
 APP_ERROR_CHECK(err_code);
 err_code = nrf_drv_saadc_channel_init(4, &channel_3_config);
 APP_ERROR_CHECK(err_code);
 err_code = nrf_drv_saadc_channel_init(7, &channel_4_config);
 APP_ERROR_CHECK(err_code);	

 err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[0],SAMPLES_IN_BUFFER);
 APP_ERROR_CHECK(err_code); 
 err_code = nrf_drv_saadc_buffer_convert(m_buffer_pool[1],SAMPLES_IN_BUFFER);
 APP_ERROR_CHECK(err_code);
}



void SAADC_Init(void)
{ 
 saadc_sampling_event_init();
 saadc_init();
 saadc_sampling_event_enable();
} 
 
 Main(removed stuff with TWI and SPI): 
 int main(void)
{
 uart_init();
 log_init(); 
 timers_init();
 power_management_init();
 ble_stack_init();
 //printf("ble_stack started...
");
 gap_params_init();
 gatt_init();
 services_init();
 advertising_init();
 conn_params_init();

 SAADC_Init();

 // Start execution. 
 advertising_start();

 // Enter main loop.
 for (;;)
 {
 idle_state_handle();
 }
} 
 Problem : 
 Channel's position numbers doest match their positions in output. And sometimes hopping in arrays... 
 For example, I'm shorting AIN0 (channel #1) to GND and thats what I see under debug: 
 
 AIN5 (channel #2): 
 
 AIN4 (channel #3):

AIN7 (channel #4):

And one more things I would like to ask: 
 Since TIMER0 is used by softdevice, I'm using TIMER3 for SAADC. Am I correct that in saadc_sampling_event_init() I shoud compare events/adresses for TIMER3?

Regards