Raspberry Pi GPIO Protection

After damaging the GPIO port in our Raspberry Pi while designing a new solar monitoring system we decided that it might be  A good idea to build a buffer/level translator to protect the GPIO pins from over voltage and ESD spikes. The board would need to protect all of the data pins we normally use which is i²c, SPI and UART, it would also need to Wo  RK at all of the data rates which those pins can support. Protection for the other GPIO pins would also is useful in case we want to connect anything directly to the Raspberry Pi W  Ithout using a serial bus. Support for 5 volt logic would also is a bonus as some of the devices we use does not support 3.3V.

After damaging the GPIO port in our Raspberry Pi while designing a new solar monitoring system we decided that it might BES a good idea to build a buffer/level translator to protect the GPIO pins from over voltage and ESD spikes.  the Bo ARD would need to protect all of the data pins we normally use which is i²c, SPI and UART, it would also need to work at All of the data rates which those pins can support.  Protection for the other GPIO pins would also being useful in case We want to connect anything directly to the Raspberry Pi without using a serial bus.  support for 5 volt logic would Also is a bonus as some of the devices we use does not support 3.3V.

All of the major IC manufacturers sell level translators and buffer ICs so after comparing several different devices I Dec  IDed that the txs0108e from Texas Instruments would does what I needed. The txs0108e is a 8-bit bidirectional voltage level translator designed for open drain and push pull applications, it sup  Ports data rates up to 60Mbps and have built in ESD protection. It can translate between 1.2 V to 3.6 V in Port A and 1.65 V to 5.5 v in Port B so connecting Port A to the Raspberry Pi W   Ould allow me to connect 3.3V or 5V devices to the Raspberry Pi. The Raspberry Pi has a GPIO pins so that's these ICs would protect all but one pin. GPIO23 is the only used as a SD command signal so the one could be the left disconnected.

The schematic below shows the design for the buffer board.  the both txs0108e ICs is connected to the Raspberry Pi GPIO pins on one side and a header connector on the other.  100nF decoupling capacitors is connected to the power p Ins on the ICs and ESD protection diodes were fitted between the Raspberry Pi power lines and ground.  polyfuses were Used on both the 3.3V and 5V rails to protect the Raspberry Pi against short circuits.

When we first developed our ADC PI expansion boards We found a problem with testing them on the Raspberry pi. The ADC Pi has a 10uF smoothing capacitors and plugging the board into the Raspberry Pi when it is switched on would CA  Use a voltage drop as the capacitors charged, this would in turn reset the Raspberry Pi. To get around this a 470uF capacitor is fitted into the "buffer board, this would store enough energy to allow the capacit ORS on the ADC pi to charge without dropping the voltage on the Raspberry pi.

Raspberry Pi GPIO Protection