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JDY-33 Bluetooth Module

JDY-33 SPP Module

A uTmax user reported an issue using these modules. There are described as being transparent and equivalent to HC-05 so should have worked out of the box. I bought one and connected to a USB to serial adapter, +5V to +5V, GND to GND, TXD to RXD and RXD to TXD to allow some testing using a terminal (TeraTerm) on my windows laptop. I found the when the Bluetooth was connected I got the message emitted from RXD:


When disconnecting, the message was


A transparent port should send nothing other than was sent from the source. The uTracer chip doesn’t understand these messages and gets confused and sends a garbled version back to the GUI. The GUI decides that the link or uTracer are in bad state and resets the link. This causes the erroneous messages to be sent again and so the cycle repeats.

I did find a datasheet that was helpful in resolving the problem, here

On page 17 was shown the very message I was seeing. Looking at the AT commands is seemed that by default status messages are enabled. These can be disabled using the AT command AT+ENLOG0. To do this you need to send serial data to the module without the Bluetooth connected.

I wrote the the following macro to use with TeraTerm. This stops the problematic status messages and renames the module to something that is more useful. I found that I needed a short pause between commands and I added an extra line feed to put the responses on separate lines. Use this to create a TeraTerm macro file ( extension ‘ttl’) and execute from TeraTerm.

send ‘AT’ 13 10 10
mpause 10
send ‘AT+VERSION’ 13 10 10
mpause 10
send ‘AT+STAT’ 13 10 10
mpause 10
send ‘AT+BAUD’ 13 10 10
mpause 10
send ‘AT+NAME’ 13 10 10
mpause 10
send ‘AT+NAMB’ 13 10 10
mpause 10
send ‘AT+PIN’ 13 10 10
mpause 10
send ‘AT+ENLOG’ 13 10 10
mpause 10
send ‘AT+ENLOG0’ 13 10 10
mpause 10
send ‘AT+NAMEuTracerSPP’ 13 10 10
mpause 10
send ‘AT+NAMBuTracerBLE’ 13 10 10

This will get the module to work with the uTracer and uTmax and gives it a recognizable name viz. “uTracer”. There remains at least one issue. The problem is that when connected over Bluetooth, it will still respond to the disconnect command ‘AT+DISC‘. This means the module can never be truly transparent and there seems to be no way to disable this behaviour. For example, if I were to try to send this very page over a serial interface using a JDY-33 SPP module, it will disconnect before completing. So, you can make it work under limited circumstances, but never in general. I understand that the same issue applies to the HC-05 and HC-06 modules. However since the disconnect command is not part of the uTracer protocol it need not concern us.