teensy_teen
Active member
Hi, are these two products fully compatible with each other? Is it as simple as plug and play like using the TC9548A with other Arduino controllers?
Hi, are these two products fully compatible with each other? Is it as simple as plug and play like using the TC9548A with other Arduino controllers?
it is better to run them at 3.3
Vin is connected to 5V (on a 3V logic Arduino/microcontroller, use 3.3V)
Thanks. In case I want to run at the highest I2C speeds, what should I do?
I can't try it myself as I have not bought a Teensy yet. I will buy it after confirmation of compatibility.
If the breakouts and sensors can take either 3.3V or 5V, in general is it better to give them 5V?
Power Pins:
Vin - this is the power pin. Since the sensor chip uses 3-5 VDC. To power the board, give it the same power as
the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
GND - common ground for power and logic
The TCA9548A may also be used for voltage translation, allowing the use of different bus voltages on each
SCn/SDn pair such that 1.8-V, 2.5-V, or 3.3-V parts can communicate with 5-V parts. This is achieved by using
external pull-up resistors to pull the bus up to the desired voltage for the master and each slave channel.
A smaller resistor will give a higher speed because of smaller RC delay, and a larger resistor will give lower power consumption.
If you want to strengthen the pull-ups from 10k to 5k, all you need to do is piggy-back extra 10k resistors on top of
(and thus in parallel with) the existing pull-ups on the PCB. This is easier and less risky than replacing the existing ones.
if adafruit posted what i quoted above, i wouldnt drive the Vin at 5v, the pullups may be pulled to Vin (didnt check schematic, just the quote)
plus as per their PDF:
Code:Power Pins: Vin - this is the power pin. Since the sensor chip uses 3-5 VDC. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V GND - common ground for power and logic
The datasheet also mentions:
Code:The TCA9548A may also be used for voltage translation, allowing the use of different bus voltages on each SCn/SDn pair such that 1.8-V, 2.5-V, or 3.3-V parts can communicate with 5-V parts. This is achieved by using external pull-up resistors to pull the bus up to the desired voltage for the master and each slave channel.
But that may be a tricky subject, will 5V devices work on the chip if it's 3.3V powered?
Given that the Teensy's Vin accepts 3.6 to 5.5V and the TCA9548A accepts 1.8-5V, can I power both of them using one or two 3.7V LIPO battery? I have a few spare ones with JST-PH connector.
How do we connect a battery to the Teensy 4.1? I don't see any connector mounted on the Teensy 4.1 board. Are we supposed to put it in a breadboard first and then power it from battery via the breadboard?
At the simplest, just attach a JST-PH connector to VIN and Ground. On the Teensy 4.0 and 4.1, you can use the ground pin between VIN and 3.3v or the other two ground pins (one next to pin 0 on the other side, or the ground pin at the set of 5 pins at the end of the Teensy 4.0 or the the set of 5 pins just before the micro SD card on the Teensy 4.1. Just make sure you remove the battery when you plug the Teensy into the USB connection for programming. You could do it with wires, or since the pins are adjacent, you could use one of these JST PH connectors using other pins in a breadboard, soldering header pins to the '+' and '-' pins that are adjacent:
There is a solder jumper pad underneath the Teensy that controls whether the VUSB pin is linked to the VIN pin. This solder jumper pad is normally connected. If you cut the solder connection, when you plug in the USB cable, it will not power the Teensy. So you would need to use the battery power to power the Teensy.
Alternatively, if you cut the jumper, you could use the 3 pins, VIN, VUSB, and ground, and hook up a battery charger. Note, you would need to connect the VUSB pin directly, since it is not normally connected, and you wouldn't be able to use it in a normal breadboard setup. For example, this little unit can be used, using jumper wires to connect the 3 pins:
If you are willing to solder the Teensy, these boards were designed to match the Teensy LC, 3.x, and 4.x pinout:
- https://www.tindie.com/products/onehorse/stbc08-high-current-lipo-battery-charger/
- https://www.tindie.com/products/onehorse/lipo-battery-charger-add-on-for-teensy-31/
I prefer the first one to the second, as it charges larger batteries faster. It also does not use pin 1 as the charging status (using pin 1 would prevent you from using the first Serial port).
Adafruit made this Teensy -> Feather adapter that includes a JST-PH connector and automatic charging support. With the Adafruit board, you do NOT need to cut solder jumper between VIN and VUSB. Instead, the board uses VIN, and if there is power available on VIN, it will use that power to charge the battery. If there is no power on VIN, it will connect the battery to provide power.
The Teensy 4.0 is the same shape as the Teensy 3.2 that the Feather Adapter was made for. If you wanted to use the Feather adapter to connect to Adafruit Feather wings, there are a few things you need to do:
For the Teensy 4.1, you need to adjust how you would connect the Teensy, since the Teensy 4.1 is longer. Either you use female headers to raise the Teensy up, so the board clears the JST PH connector, or you mount the Teensy underneath the feather adapter.
I prefer the Teensy Feather adapter to the other methods because the JST PH connector is more solidly attached. When I've soldered a JST PH connector to a prototype board, I have to be real careful in removing and attaching a battery. I have pulled off the JST PH connector a few times.
Generally, I use stacking headers on the Teensy, so that I can mount things either below or above the Teensy.