Which board for which job
Two questions decide it: does the signal rely on a pull-up resistor, and is it fast? The chooser and the table answer them for the six things people actually connect.
Two questions
- Is the line held HIGH by a resistor? I²C, 1-Wire and a button all are. That rules out the TXB0108.
- Is it fast? SPI and LED strip data are. That rules out the MOSFET boards, or at least makes them a gamble.
The TXS0108 passes both questions, which makes it the safe default when you are unsure. The other two are each the best choice for their own job.
The whole table
| Connecting | MOSFET 2/4/6CH | TXS0108 | TXB0108 |
|---|---|---|---|
| I²C sensor or screen | yes | yes | no |
| Serial (UART) | yes | yes | yes |
| SPI display or SD card | slow clocks only | yes | yes |
| WS2812 LED strip | marginal | yes | yes |
| DS18B20 (1-Wire) | yes | yes | no |
| Button or switch | yes | yes | no |
Mixing boards in one project
Nothing stops you using two. A 2CH for an I²C screen and a TXB for an LED strip can sit on the same breadboard, sharing the same 3.3 V, 5 V and ground rails. Each board still needs its own LV, HV and GND wires.
When it does not work
Ask the two questions. Is the line held HIGH by a resistor, with devices only pulling it LOW? Then not the TXB. Is it faster than a few hundred kHz? Then not the MOSFET board. A slow PWM signal to a motor driver, for example, is driven both ways and slow, so any board will do.
Do not try to make it work. TI's datasheet rules the TXB out for I²C, and a bus that half works is harder to debug than one that does not work at all. A 2-channel MOSFET board is the right part, and there are eighteen in the 27-pack.
No. These boards are for digital signals only. Through a TXB or TXS an analog voltage becomes a 0 or a 1, and through a MOSFET channel it gets distorted. To scale an analog 0–5 V down to 0–3.3 V, use a voltage divider.
The commonest build in this book, from wiring to a working bus scan.
A 5 V I²C screen on an ESP32 →Edit this page — content/books/llc/which-board-for-which-job.mdx
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