TWI on nRF51822

Question

I just entered a Case to Nordic with this same question but do not expect to get a response over the weekend so I am posting here. I made the assumption that the Nordic Cases and the Developer Zone are not related. If this is considered a double-post I apologize. 
 I used the RF6350_radio_configuration_example as a starting point for our TWI interface. The goal is for the nRF51822 to act a a Master and send commands to a Slave to read/write the Slave's RAM/EEPROM. 
 I am using the nRF51822 EK with our TWI Slave attached and uVision 4 and the TWI transmission are unsuccessful. When a command is issured there are two negative SDA pulses followed by continuous SCL pulses. (36 usec period = 27.8KHz). The Slave requires clock freuencies of 10KHz-100KHz. When the code reaches “if (timeout == 0)” in the twi_master_write() while loop timeout always equals 0 which may be why the transmissioin fails. Of course this may not be the only problem. 
 I am still plugging away on this but time is short so any suggestions will be appreciated. 
 twi.txt

Tielman · Accepted Answer

Hi Tom 
 If the softdevice is enabled, you can not access the PPI directly as you have done in your code. You have to use the softdevice API to access the PPI. The PPI is mentioned as restricted in the softdevice specification, which means you must access it via the sd API. As example, the following code strip 
 NRF_PPI->CH[0].EEP = (uint32_t)&NRF_TWI1->EVENTS_BB;
NRF_PPI->CH[0].TEP = (uint32_t)&NRF_TWI1->TASKS_SUSPEND;
 
 should be replaced by
 sd_ppi_channel_assign(0, &NRF_TWI1->EVENTS_BB, &NRF_TWI1->TASKS_SUSPEND); 
 All the NRF_PPI references need to be replace by sd_ppi_* equivalent commands. 
 I did not notice that your softdevice is enabled (or disabled for that matter) in your code, but the code file you sent is probably a summarized version of your actual code? If you are using BLE in your project, then it is probably enabled in which case you have to modify the code as I have indicated above. As quick reference, simply do the following replacements in your code (with the above example as well): 
 NRF_PPI->CHENCLR = PPI_CHENCLR_CH0_Msk; 
should be
 sd_ppi_channel_enable_clr(PPI_CHENCLR_CH0_Msk); 
 NRF_PPI->CH[0].TEP = (uint32_t)&NRF_TWI1->TASKS_STOP; 
should be
 sd_ppi_channel_assign(0, &NRF_TWI1->EVENTS_BB, &NRF_TWI1->TASKS_STOP); 
 NRF_PPI->CH[0].TEP = (uint32_t)&NRF_TWI1->TASKS_SUSPEND; 
should be
 sd_ppi_channel_assign(0, &NRF_TWI1->EVENTS_BB, &NRF_TWI1->TASKS_SUSPEND); 
 Hope this helps

TWI on nRF51822

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