Good afternoon,
I am trying to use a function generator to send a sinusoidal function to my nRF7002 DK and I am vizualizing the values in Putty. I am sending with a frequency of 100kHz, 1.5 Vpp. I observed that I get a lot of values of -4096, which it`s the maximum value I can get with the SAADC. Why that might be the reason for reaching that value so easily? On the positive side, my maximum is 1200 or so.
Thank you.
Hi Raluca
It sounds to me like there might be some configuration issues here. Could you please provide the following information:
1. SDK version
2. Your prj.conf
3. Your device tree
4. The ADC part of the application
Regards
Runar
Hello!
1. SDK version: v2.5.99 - dev1. Answering this I realized I am in a dev branch, I will change and test it again.
2.This is my prj file.
CONFIG_LOG=y # Step 1 - Enable nrfx drivers # CONFIG_NRFX_SAADC=y CONFIG_NRFX_PPI=y CONFIG_NRFX_DPPI=y CONFIG_NRFX_TIMER2=y CONFIG_LOG_BUFFER_SIZE=16384
3. My device tree:
/dts-v1/;
#include <nordic/nrf5340_cpuappns_qkaa.dtsi>
#include "nrf5340_cpuapp_common.dts"
/ {
model = "Nordic NRF5340 DK NRF5340 Application";
compatible = "nordic,nrf5340-dk-nrf5340-cpuapp";
chosen {
zephyr,sram = &sram0_ns;
zephyr,flash = &flash0;
zephyr,code-partition = &slot0_ns_partition;
zephyr,entropy = &psa_rng;
};
psa_rng: psa-rng {
compatible = "zephyr,psa-crypto-rng";
status = "okay";
};
};4. The configuration of the ADC:
static void configure_saadc(void)
{
nrfx_err_t err;
/* STEP 5.4 - Connect ADC interrupt to nrfx interrupt handler */
IRQ_CONNECT(DT_IRQN(DT_NODELABEL(adc)),
DT_IRQ(DT_NODELABEL(adc), priority),
nrfx_isr, nrfx_saadc_irq_handler, 0);
/* STEP 5.5 - Initialize the nrfx_SAADC driver */
err = nrfx_saadc_init(DT_IRQ(DT_NODELABEL(adc), priority));
if (err != NRFX_SUCCESS)
{
LOG_ERR("nrfx_saadc_init error: %08x", err);
return;
}
/* STEP 5.6 - Declare the struct to hold the configuration for the SAADC channel used to sample the battery voltage */
nrfx_saadc_channel_t channel = NRFX_SAADC_DEFAULT_CHANNEL_SE(NRF_SAADC_INPUT_AIN0, 0);
/* STEP 5.7 - Change gain config in default config and apply channel configuration */
channel.channel_config.gain = NRF_SAADC_GAIN1_6;
err = nrfx_saadc_channels_config(&channel, 1);
if (err != NRFX_SUCCESS)
{
LOG_ERR("nrfx_saadc_channels_config error: %08x", err);
return;
}
/* STEP 5.8 - Configure channel 0 in advanced mode with event handler (non-blocking mode) */
nrfx_saadc_adv_config_t saadc_adv_config = NRFX_SAADC_DEFAULT_ADV_CONFIG;
err = nrfx_saadc_advanced_mode_set(BIT(0),
NRF_SAADC_RESOLUTION_12BIT,
&saadc_adv_config,
saadc_event_handler);
if (err != NRFX_SUCCESS)
{
LOG_ERR("nrfx_saadc_advanced_mode_set error: %08x", err);
return;
}
/* STEP 5.9 - Configure two buffers to make use of double-buffering feature of SAADC */
err = nrfx_saadc_buffer_set(saadc_sample_buffer[0], SAADC_BUFFER_SIZE);
if (err != NRFX_SUCCESS)
{
LOG_ERR("nrfx_saadc_buffer_set error: %08x", err);
return;
}
err = nrfx_saadc_buffer_set(saadc_sample_buffer[1], SAADC_BUFFER_SIZE);
if (err != NRFX_SUCCESS)
{
LOG_ERR("nrfx_saadc_buffer_set error: %08x", err);
return;
}
/* STEP 5.10 - Trigger the SAADC. This will not start sampling, but will prepare buffer for sampling triggered through PPI */
err = nrfx_saadc_mode_trigger();
if (err != NRFX_SUCCESS)
{
LOG_ERR("nrfx_saadc_mode_trigger error: %08x", err);
return;
}
}
Maybe it will be clearer if I attach the entire project as well.
Thank you so much!
Hi
Is your signal centered around 0V? if so it will be outside the GPIO range which has a minimum level of -0.3V. If this is the case, could you try to add a positive DC offset and see if the problem is exist?
Regards
Runar