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The Direct Test Mode (DTM) is a standard mechanism defined by Bluetooth Special Interest Group (Bluetooth SIG) to test the radio frequency (RF) performance of Bluetooth devices for all Bluetooth channels. In general, DTM is used in application validation and product line tests, enabling RF engineers to effortlessly verify and optimize Bluetooth RF performances. Tested RF factors include:

  • Transmission power and receiver sensitivity
  • Frequency offset and drift
  • Modulation characteristics
  • Packet error rate

The DTM test on GR551x System-on-Chips (SoC)s is based on UART physical interfaces and a Bluetooth tester. The Bluetooth tester controls GR551x RF physical layer (PHY) by using Host Controller Interface commands (HCI CMD) to implement test procedures.

Before getting started, you can refer to the following documents.

Table 1 Reference documents
Name Description
GR551x Developer Guide Introduces GR551x Software Development Kit (SDK) and how to develop and debug applications based on the SDK.

Keil User Guide

Offers detailed Keil operational instructions. Available at

RF PHY Bluetooth Test Suite TS

Introduces RF PHY test specifications. For Core-Test Requirements, see .

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