Hi,
In micro_esb.h, it is indicated that the transmission without ACK is not implemented yet. However, there is a parameter named dynamic_ack_enable in the uesb_config structure and a function named uesb_write_tx_payload_noack(..) which are not functional yet, when trying to communicating from nRF51 to nRF24.
Are you working on this problem ? Is it possible to write with no ACK between two nRF51 ?
Regards !