TWI SDA check for NACK

RE: TWI SDA check for NACK

matthk — Thu, 07 Sep 2017 16:00:49 GMT

You are right Martin: the EEPROM address is 0xA0/1 - only the ECAD designer who designed the electronics in Altium was obviously reading 0x10 at my schematics paperwork and didn't discover that it is an 'A' and not a '1'... Now I know that the EEPROM can be read and written; unfortunately not the TMP108; I have to check this now....Thanks for your help!

RE: TWI SDA check for NACK

MartinBL — Thu, 07 Sep 2017 15:19:27 GMT

What is the serial number of the EEPROM? My bet is that it is the EEPROM that answers. 50h is not one of the possible addresses of the TMP108. 0xA0 is an 8 bit number and is probably not what you should refer to in the documents or code. Please have a look at this thread.

RE: TWI SDA check for NACK

matthk — Thu, 07 Sep 2017 07:43:36 GMT

Hi Martin, I have a good and a bad news: The good one: Scanning did work. The bad one: Only one device was found, at that at the address 80d = 50h; also at the oscilloscope I see the ACK when sending to 50h which would mean an I²C address of 0xA0/1 instead of 0x90/1. Actually I try to find out if the device is the TMP108 or the EEPROM...

Do you have any idea how this is possible? I tried it already with another electronics (same type), but same behavior - strange...

RE: TWI SDA check for NACK

MartinBL — Wed, 06 Sep 2017 13:37:13 GMT

Hi,

If you use the TWI drivers from Nordic you should use address 0x48 to 0x4B for the TMP108, dependent on your A0 pin configuration. From the TMP108 datasheet:

You don't need to left shift this address or add any TWI read/write bits at the end. That is all handled in the nRF52 hardware.

I'll advise you to try the TWI Scanner Example. This example will scan all possible TWI addresses and give you an output if a slave device is answering. If a slave responds, then the returned address is the address you should use throughout your code. If no devices respond then you have a TWI driver configuration issue or an external hardware issue.