TWI on nRF51 DK (nRf51422) with s110

RE: TWI on nRF51 DK (nRf51422) with s110

Faizan — Wed, 27 May 2015 11:26:37 GMT

U refers to unsigned constant. Its a good practice to define the unsigned constant with U as suffix. This tells the compilers to store it as unsigned value.

RE: TWI on nRF51 DK (nRf51422) with s110

Guilherme de Paula — Thu, 16 Apr 2015 03:46:17 GMT

I works like a "type cast" to an "unsigned int" constant.

RE: TWI on nRF51 DK (nRf51422) with s110

RK — Wed, 15 Apr 2015 23:19:00 GMT

'U' is C-syntax for an unsigned constant. So 24U means 24.

RE: TWI on nRF51 DK (nRf51422) with s110

Guilherme de Paula — Wed, 15 Apr 2015 17:34:49 GMT

Please post your code/hw info so we can try to help you (initialization, main loop, schematics for the board, etc). I've used the TWI with nRF51822 without any problems.

RE: TWI on nRF51 DK (nRf51422) with s110

Max C. — Wed, 15 Apr 2015 17:10:54 GMT

You haven't written so much details on the code you used to make TWI working so it is a bit hard to say something;

Do you have initialized the TWI peripheral (IO lines, speed, etc..)? Do you have configured the pull-up for that lines (check if the board has pull-up resistors on that lines)? Do you set the tasks properly to start the communication on the bus (TASKS_STARTTX when writing, TASKS_STARTRX when reading)?

RE: TWI on nRF51 DK (nRf51422) with s110

Nerdwolf — Wed, 15 Apr 2015 07:42:51 GMT

I finally got it to work. I was very confused by another topic answer stating that 24U and 25U was hexadecimal for pin P18 and P19. So i was using the wrong pins :). Can anyone clarify why the 'U' in the twi pin declaration has been added ( and thus my confusion). E.g: with spi there is no 'U' in the pin declaration. But in both cases there is just refered to the physical pin number for example P0.01,P0.24,..?

Thanks!