Teensy 4.0 instead teensy 3.2

E

EGM39

Member
Hi all,

I'm working with teensy 3.2, I try to change it for teensy 4.0. I need some help.
I use analogs & digital pins and the serial3 (serial2 in the teensy 3.2).
I connect the teensy 4.0 directly into the PCB with the connection TX & RX from the Hc-06 to Pin14 & Pin 15 on the teensy to send and receive through serial3.
I can see data with my phone so the teensy is sending values but I can't send date with the app in windows.

Any help plz
 
Please tell us exactly which hc-06 module is connected to Teensy. Provide a weblink or datasheet of the exact module.

Some of these modules send serial data with 3.3V as a logic 1. That's good since Teensy 4.0 is not 5Volt tolerant. However, some of these modules send serial data with 5V as a logic 1. 5Volts damages the T4.0 GPIO pin or destroys T4.0 completely. Since your T4.0 isn't receiving data from HC-06 (from PC), it's possible the GPIO pin is damaged.

It's also possible you have a bad solder connection. Might want to check those.

If you have a volt meter, can you measure the voltage of TX and RX pins. Let us know the results.
 
Hi both

My diagram is this. Im using 3.3V for them.

I conect the device as you see the next down corner. Here

The voltage in the RX on the HC-06 is 3.3V but the voltage in TX is 20mV. I received date from HC-06 (I checked it in my phone with a terminal) but nothing is sending.

I tried to put a 1K resistor between TX and 5V pullup resistor but it didn't work.

I have another circuit similar with teensy 3.2 is working but then I use another teensy 3.2 and it happens exacly the same than with teensy 4.0 and this circuit. Im missing something....the voltage in TX on the HC-06 is 20mV.

Any idea is very welcome

Thanks!
 
You say you're using 3.3V but that schematic very obviously shows everything being powered by 5V.
Having the LED being run directly from an IO pin isn't great either, the resistor isn't high enough to prevent it from pulling more than 4ma.
 
EGM39 said:
I mean that I use 3.3V in the pin16 and pin17 in the teensy.
Click to expand...
Are you sure? It looks like the sensors connected to them are powered by 12V, if they're returning 12V signals those 10K/20K resistors will only be dividing down to 4V which is still too high.
 
Hi,
Voltage that I have approx values.

Voltage R4 2.76V (output from sensor 2)
Voltage R3 1.84V (pin17 teensy)
Voltage R2 2.49V (output sensor 1)
Voltage R1 1.66V (pin16 teensy)

Voltage pin14 teensy 4.0 is 3.3V
Voltage pin15 teensy 4.0 is 0.04V
Voltage pin16 teensy 4.0 is 1.53V

Voltage in pin 15 in the teensy is the problem

THanks for your help
 
Teensy 4.0 will be dead but what is happening with teensy 3.2? Im using pin RX2 pin9 and pin10 TX2 serial2.

If is 5V input for teensy 3.2 is dead as well?
 
BT-module TX level at 0.04 is not correct.
UART idle level is "1", 3V3 or 5V, depending on devices.
What is the voltage on BT-module TX when you remove The Teensy ???
 
Hello @EGM39.

Please read my post #2 above.
Until we know the EXACT manufacturer part number of BT-module, we are guessing at the voltages. Or, provide a weblink showing where you purchased it.

As for T3.2, it has 5V tolerant GPIO pins. That's why it will not be damaged. T4.0 (and T4.1) will be damaged if GPIO pin sees 5V.
 
Hi
Sorry I missed that message
I include the place where I ordered and pictures.

Amazon link

Picture device

Im ordering some from a property places anyway.

Problem with teensy 3.2 is the BT device
Problem with teensy 4.0 should be use 3.3V in Vin instead 5V that it's correct?

Thanks
 
I don't know anything about this specific HC-06 module. But for any type of serial comms, 3.5mV is not good.

When idle, serial is logic high, which could be either 3.3V or 5V. But 5V signals are very unlikely with anything Bluetooth. Usually only much older stuff uses 5 volt signals. Odds are anything new enough to be Bluetooth will use 3.3V logic-high signals.

During data flow, the transmitter sends a start bit with is logic low, then 8 data bits which can be either low or high, and 1 stop bit which is logic high. So even in the case of continuous data flow where all data bits are 0, at least 1 of every 10 bits transmitted would be logic high. So a DC voltage measurement would see an average voltage of at least 0.033 volts (33mV). There is no valid serial data flow that can result in a measurement of only 0.0035 volts (3.5mV). Voltage that low is a sure sign of wrong correction or damaged hardware. Only 3.5mV simply can not happen in any correctly operating serial communication.

I don't know what's wrong.

Maybe the problem is a mistake or misunderstanding with wiring? If you show photos of your wiring, maybe we could be able to see something you've missed? Actually seeing the wiring might also help us to understand these measurements you've given.
 
Based on schematic DSD Tech points to for their HC-06 product (minus the RS232 converter):
DSD TECH BT-06, the entire module is power by a 3.3V regulator. However, there is a 10k Ohm pull-up resistor to 5V on the module TX output. This will limit T4.0 damaging current. So, maybe only the T4.0 GPIO pin is damaged. HC-06 TX output should not be damaged although this is what you observed with Low around 3.5mV.

5V applied to T4.0 Vin is correct.

I suspect you have a soldering short circuit on HC-06 Tx signal somewhere. Solder short is either at the T4.0 or at the other end (HC-06). Let's see if we can isolate the problem.
With everything wired up as you want it, disconnect only the HC-06 TX output wire at the HC-06. Now, power everything up and measure the voltage at HC-06 TX pin and measure the HC-06 5V input pin. Be sure to measure on the pin, not on the wires.
If you observe 5V at both of these pins under this test condition, the issue is either with wiring, soldering, or problem with T4.0.
Now, leaving everything setup as above, measure Teensy RX pin.
Let us know the results.

Can you upload a photo of T4.0 soldering and the HC-06 soldering?

BTW, you should not connect T4.0 USB to PC USB when using the ATX power supply. The PC USB supplies 5V to T4.0 on USB cable and this will fight with ATX 5V supply. If you need USB and ATX at the same time, there are a few options. See T4.0 back-side of card <here> to locate 5V pads. Then, select an option from <here>. The weblink shows a different Teensy, but the result is the same for T4.0. And, think of the ATX supply as if it was the battery being shown.

<edit>
Are there any components on the backside of HC-06? There aren't any photo's of backside available. The reason I ask is, it's not clear to me if the DSD Tech schematic at the weblink they provide, is representative of the module you have. For example, the schematic shows an RS232 chip. But, there's only TTL TX/RX signal connections according to DSD Tech product description (at amazon and DSD Tech websites). So, I've assumed the 10k Ohm pull-up resistor to 5V is installed on HC-06 TX output pin. This could be a wrong assumption.
With the module powered OFF and TX pin wiring disconnected, measure the resistance from TX pin to 5V pin on HC-06 module. Maybe you'll observe 10k Ohms, maybe you won't.
 
Last edited:
Hi all,

Good news!
5V is correct to teensy 4.0

There were the BT module HC-06, the new ones arrived and I checked it and they works perfectly!!

I will check the 10K resistor, probably is just this version of the BT device.

Thanks for your help! Useful! 🙂
 
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