About the article

TTL Bluetooth Dongle

Wireless data comms made easy

TTL Bluetooth Dongle
Need to connect your circuit to a PC to transfer measurement values or data? How about wirelessly? If you think that would be way too complex, think again. The solution offered here is a Bluetooth device which from your circuit’s point of view looks just like a UART with a PC (or other device) attached to the other end. It’s as simple as plugging in a USB to TTL cable but without the wires!
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info / Update


- SPP Protocol fully Integrated 'on chip' (other Bluetooth devices behave as if they are connected via a serial cable)
- No configuration necessary in slave mode, Plug & Play like a USB to TTL cable
- Module can be configured as master via the UART allowing two modules to communicate
- Communication up to 921600 Baud (configurable from 2400 to 921600 Baud using jumpers or software)
- 5 V supply uses an on-board voltage regulator
- Pin compatible with the USB to TTL adapter cable from FTDI
- Direct interface with microcontroller (3.3 V) possible
- UART including handshake signals
- 2 LEDs indicating Bluetooth link status and traffic
- Expansion with an external audio codec possible
- Low power mode using optional 32 kHz crystal

Component list
Resistors (all 0805)
R1,R2 = 330Ohm (1%)
R3..R5 = 1kOhm (1%)
Capacitors (all 0805):
C1–C5 = 100nF
C6..C8 = 2µF2
C9,C10 = 22pF
D1 = LED, blue, SMD
D2 = LED, red, SMD
IC1 = LMS8117-AMP3.3
IC2 = LMX9838SB
X1 = 32.768kHz quartz crystal (CL = 6pF, 20ppm)
K1 = 6-pin SAL pinheader, 2.54mm pitch, right angled
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