Raspberry Pi Forums

I have been struggling to get my keyboard to connect to the Raspberry Pi. I arrive at the Raspian Setup screen and the keyboard is inoperative. I have read several of the posts, one of which says the voltage between TP1 and TP2 must be at least 4.75V. On mine it is 4.63 V. Does this mean that the Pi is malfunctioning and I should send it back?

No, it is more likely that your Power Supply or even more likely, the MicroUSB Cable you are using is not up to the job.

There is a polyfuse immediately after the MicroUSB socket on the RPi board and this is known to add a small Voltage drop to the terminal voltage of the PSU. This can account for the voltage measured between TP1 and TP2 being ~ 100mV less than expected.

On the Rev 2 Board and later Rev 1 Boards, the polyfuses at the USB Sockets have been removed so it is feasible to power the RPi from a powered USB Hub, itself fed from a good PSU. This also circumvents the contact resistance of the flimsy MicroUSB Plug/Socket as the USB A contacts are meatier.

Many Keyboards and Mice will not work below 4.7V and even if they do appear to work, you are likely to have "typamatic" problems.

Thanks. I tried a really good quality lead and a variety of power sources.....nothing. After three days of trying everything, I'll have to send it back - before it puts my son off the joys of computers!

If you are measuring less than 4.8V between TP1 and TP2, there is likely to be nothing wrong with the RPi and sending it back will not restore your son's enthusiasm for computing.

What do you mean by "good quality leads"? I have bought more than a dozen MicroUSB cables and none of them are capable of carrying more than 500mA without dropping a Volt at the load end.