3. How DA1453x Boots from RX host MCU ?

3.1. overview

The DA1453x Bluetooth low energy devices don’t feature any on-chip flash, the program code is executed from on-chip RAM. In this document we will focus on the host Configuration where the DA1453x image is stored in flash on the host MCU. At boot time the MCU then loads this code into DA1453x RAM. The Renesas MCU and BLE (DA1453x) chips are connected via a 4-wire UART and communicate with each other over Renesas’s proprietary GTL interface. The GTL interface will be detailed later on in this document.

../_images/host_config.svg — Figure 3 **Host Configuration**

3.2. boot options

The DA1453x bootloader serial protocol is documented in the UM-B-119 DA14585-DA14531 SW Platform Reference. The host MCU can initiate the download process by resetting the DA1453x via the reset pin (P0_0). More details in Section 7.1.

../_images/boot.svg — Figure 4 **Boot DA14531 from host MCU: implementation**

3.3. Setting Up the CK-RX65N dev kit and the DA14531 Pmod™

3.3.1. Introduction

This document is based on the US159-DA14531EVZ Pmod™ (DA14531 Pmod™) which incorporates the DA14531-00 SmartBond TINY™ Module and can ONLY be booted via 1-wire UART this is because the P0_0/P0_1 which are the Two-wire UART pins, are used to connect with the internal flash. The next section will explain how to boot using a 1-wire UART and switch to a 2-wire UART for operation. More information in DA14531 Module Datasheet.

../_images/1-wire.svg — Figure 5 **1-Wire UART configuration**

3.3.2. HW setup

Attach the US159-DA14531EVZ BLE Pmod™ to Pmod™ 1 (J26, upper Left). The DA14531 Pmod™ module and components should be facing up.
Connect the CK-RX65N dev kit to the PC using a USB micro-B cable connected to DEBUG (J14) on the board (right side of board above Ethernet jack).
Once completed, the LEDs (white LED 1 and green LED5) should be illuminated as described below, and the connected boards should look like depicted below.
- LED4 (middle of board) Illuminating white
- LED5 (right side, near USB debug port) blinks green.

../_images/board_connected.svg — Figure 6 **Setting Up the CK-RX65N dev kit and the DA14531 Pmod™**

Warning

A 1K ohm resistor should be added between UART RXD and TXD in order to boot the DA14531 Pmod™ from an RX Host microcontroller.