switching between channels in the fastest way possible

Hi mechatronics ,

Have you configured the ADC with CHOP ENABLED or DISABLED?

As the ADC powers up and performs a single conversion, you should take note that the oscillator requires 1 ms to power up and settle. The ADC then performs the conversion, which takes a total time of conversion time plus settling time when chop is disabled. With chop enabled, the settling time is two times the conversion time.

So, you may want to configure the ADC with CHOP DISABLED. Can you please confirm if have set MR3 to MR0 of the MODE REGISTER to 0001? 

Could you share your configuration settings if possible? 

Thanks and regards,

Rod

Hi Rod,

thanks for your reply i really appreciate your helping and thanks for your time.

1- i am sure that i have CHOP disabled in my code, i set the mode register to 0x0211.

MD2-MD0 = 000 which is continuous conversion mode (i know using single conversion mode might be better for my work but i really struggle doing that i could not succeed)

AMP-CM enabled (bit 9=1)

CHOP Disabled (bit 8 =1)

FS bits =  0001 meaning 470Hz sampling based on the datasheet 

the exact code is : 

uint16_t mode_value = 0x0211;
write_register(MODE_REG_ADDR, mode_value);

2- MR3 to MR0 : yes as you said it is 0001

3- Oscillator startup delay: I do perform a reset on the ADC at startup using 32 clock pulses (0xFFFFFFFF over SPI), and I insert a 2 ms delay afterward (HAL_Delay(2);) before proceeding. So I believe I am accounting for oscillator settling at power-up.

4-  now i read 6 channels like this: 

Writing to the configuration register to select the channel

Rewriting the mode register (again with 0x0211)

Waiting for RDY bit to go low

Then reading the data register

but, the full scan across 6 channels takes about 1.2 seconds, which is far from the performance i need.

5- i select the channels like this: 

void select_channel(uint8_t channel, uint16_t config_value)
{
config_value &= 0xF000; // clear previous channel/gain bits
config_value |= (0x07 << 8); // Gain = 128
config_value |= (channel & 0x0F); // Channel select
write_register(CONFIG_REG_ADDR, config_value);

// Wait for conversion to complete
while (read_register(STATUS_REG_ADDR) & 0x80) { }
}

i think these cover's your questions. I am really looking forward to your advice to make my data acquisition process as fast as possible.

Again thanks for your time i sincerely appreciate your help.

i can also provide my full code and settings.

Thanks again and best regards.

hi again RAdante 

I have replied again as a reminder to tell you i look forward to your help if you be kind ad put your time.

i still suffer from the same problem and i have issues with the speed of my work

Regards

Hi mechatronics 

Apologies for missing the thread. 

Have you tried exploring the continuous read mode? 

Since you set the ADC inn continuous conversion mode, the ADC continuously performs conversions and places the result in the data register. With this, you can read these conversions by placing the device in continuous read mode whereby the conversions are automatically placed on the DOUT/RDY line when SCLK pulses are applied. 

You can do this rather than writing to the communications register each time a conversion is complete to access the data and see if it improves your setup.

mechatronics said:

i can also provide my full code and settings.

• Yes, this would be great. It would help give a wider perspective on how the ADC was configured and is being used. 

Thanks and regards,

Rod

Hi RAdante 

I have applied your suggestions to my ST code and now it works perfectly and satisfies my desires 
i really appreciate your effort and thanks for your time 

Regards.

Hi mechatronics ,

That's good to know, we appreciate your engagement. If you have any further questions, please feel free to post them on our forum, we're here to help.

Thanks and regards,

Rod