nRF52840 module and SHT21 sensor

[Hannu Hirvonen]

Hello,

Is there someone who has worked recently with nRF52840 and SHT21 (Humidity / Temperature) sensor ? I have to do some basic test for HW and validate that sensor is working properly ? I have seen that over 3 years ago there was some discussion about that. Basic tests I can do without SD. Of course it is nice to see valid temperature and humidity values at least in debugging console (why not in UART also). 

I run twi_scanner SW and it found device 0x40 = 100 0000 = Sensirion SHT21 device. But how to validata that it really works.

Br,

-Hannu-

[Sigurd]

Hi,

A test program that verifies that the temperature and humidity are within valid ranges sounds like a good idea. An extended test could be to run the test program over time, logging the temperature, and see if it stays within the expected temperature range.

[Hannu Hirvonen]

Hello Sigurd,

Problem is that using twi_scanner project I can see device 0x40 = 100 0000 now and then. I'm not sure if problem is in SD or driver or where ? Sometimes it works fine, but sometimes doesn't. Are you familiar with this SHT21 temperature/humidity sensor using I2C / TWI ?

-Hannu-

[awneil]

Hannu Hirvonen said:

I'm not sure if problem is in SD or driver or where ?

Well, as you said in the OP, you could easily eliminate the SD by simply using a project which doesn't have the SD.

Other than that, are you checking for error reports in the code?

Have you looked at what's happening on the I2C lines with an oscilloscope?

[Hannu Hirvonen]

Hello,

Sometimes I can see SHT21 chip on I2C/TWI bus, but typically not ? When I can't see it I get error 0x00008201 = NRF_ERROR_DRV_TWI_ERR_ANACK. Just using twi_scanner example code. Any ideas how to get it working and is there someone who is familiar with this SHT21 chip ?

-Hannu-

[awneil]

Hannu Hirvonen said:

When I can't see it I get error 0x00008201 = NRF_ERROR_DRV_TWI_ERR_ANACK

So have you looked-up what that error means?

Again, have you looked at what's happening on the I2C lines with an oscilloscope?

[Hannu Hirvonen]

Hello,

I'm currently investigating with Laird DVK BL654 how to use I2C/TWI, but this twi_scanner didn't there either. If I ask help from Laird they say that ask from Nordic because I use Nordic SD (not SmartBasic) and if ask help from Nordic you say that ask from Laird because I'm using their DVK. I'm quite sure that this twi_scanner example program did't work correctly. Is it so that their is not I2C sensor in nRF52840 evaluation board ? It should help much when investigating how does this I2C/TWI work in practice.

-Hannu-

[awneil]

You've missed the point!

You need to ask Laird for answers to specific questions about their products - like whether their module has an RTC chip, and how it is connected, etc. Nordic cannot help you with that.

Nordic can help you with things that are not specific to Laird - like how to use the nRF52840's TWI peripheral.

Hannu Hirvonen said:

It should help much when investigating how does this I2C/TWI work in practice

Do you understand the basics of how I2C works?

It is an industry standard - not specific to Nordic.

Start here:

https://www.nxp.com/docs/en/user-guide/UM10204.pdf - I2C Specification

https://en.wikipedia.org/wiki/I%C2%B2C

Are you familiar with software development in general, and embedded microcontrollers in particular?

When an API function returns an error code, that code will give you information about what's gone wrong - so it is important that you look-up the documentation of the error code.

So, again, have you looked up the meaning of the NRF_ERROR_DRV_TWI_ERR_ANACK error code?

You can use your IDE's search/browse facilities to find it.

Or just put "NRF_ERROR_DRV_TWI_ERR_ANACK" into google:

https://devzone.nordicsemi.com/f/nordic-q-a/21891/nrf_error_drv_twi_err_anack-in-blocking-mode

https://arduino.stackexchange.com/questions/21850/what-does-it-mean-in-i2c-nack-received

[Hannu Hirvonen]

You didn't understood my question correctly. I know that there is a RTCC chip in Laird DVK BL654, but because I don't use them SmartBasic but your SoftDevice they can't help (and don't help) because it is your stuff.

Yes I know how I2C/TWI works.

I'm familiar with SW development since 1988, when you started ? With microcontrollers started 1993, when you ?

I have heard something that return codes does help sometimes :)

-Hannu-

[Hannu Hirvonen]

Hello,

Case solved. twi_scanner can't "scan" SHT21 sensor, but when reading and writing directly using address 0x40 sensor works fine. No I at least know quite well how TWI works and big thanks for PicoScope

-Hannu-