What goes where on the new Raspberry Pi 4
- A 1.5GHz quad-core ARM Cortex-A72 processor with Video Core VI graphics. The beating heart of the new Raspberry Pi model may not be much faster than the previous version in terms of clock cycles, but the more powerful cores mean that it can do more processing for each clock tick.
- The LPDDR4 RAM is faster than in previous models and now comes in 1GB, 2GB, and 4GB variants.
- WiFi and Bluetooth remain largely unchanged, but now supports dual screens.
- The display connector for linking with the official touchscreen display.
- The VLI USB chip connector gives USB 3.0 capabilities.
- The BCM54213PE chip connects the Ethernet to a high-speed interface to the CPU.
- The PoE header allows you to power your Raspberry Pi from compatible Ethernet networks, meaning you can use a single connector for power and networking.
- The audio port also functions as composite video out.
- The micro HDMI connector for connecting to a monitor (see box below).
- There’s a second micro HDMI connector to let you use dual screens.
- USB-C provides 5V at up to 3A of current.
- The GPIO header retains the classic layout, but now also includes four UARTs, four SPIs, and four I2Cs.
- The microSD card connector has twice the bandwidth of previous versions.
- The Gigabit Ethernet connector has switched sides and is now next to the GPIO header.
- The two USB 3.0 ports are identifiable by their blue tongues.
- There are an additional two USB 2.0 ports that run slower than the 3.0 ports, but are still fine for most uses.
Micro HDMI
We asked Raspberry Pi (Trading) Ltd COO and designer James Adams what went into making sure the micro HDMI connectors were robust enough for everyday use. Here’s what he had to say:
“These things are much smaller than the standard HDMI, and therefore more fragile, so it’s a thing that we were concerned about. We worked hard with two connector manufacturers [to mitigate this].
“If you look at the micro HDMI ports on the board, there are some flares that we added. That helps for two reasons. It helps the user insert the plug, and it helps with robotic tests. We have high volume, so we can work with suppliers and do great custom stuff. We did other things – we changed the geometry of how the shell attaches to the PCB, and we also did a load of work to effectively vet the connectors.
“One of the out-the-gate connectors was substandard, and the manufacturer completely re-engineered it to get it up to our standards. We’ve taken samples through multi-cycle testing: so, put a connector on a machine and put the connector in and take it out 5000 times, and get a graph of the insertion and exit force over time, and look at the things and see if they survive. For sure, they’re going to be a bit more fragile than the really big, chunky HDMIs, but we’re confident they’re fine. They should be a lot better than an off-the-
shelf connector.”
USB-C
Raspberry Pi 4 has a different power connector to previous boards. We asked James Adams if this was here to stay:
“The answer’s yes for the foreseeable future. USB-C’s great. The pins are designed for more current – the old micro B connector was 2.5 amps, and we were pushing it a bit in terms of what it could do, but the USB-C is designed for 3 amps minimum, so we can do 3 amps at 5 V.
“In the future, we could possibly use the PD power modes to turn the voltage up and get even more power into the board in some fashion. For power for Raspberry Pi, I think it’s the right answer. Never say never – you don’t know what’s going to come along next – but it seems like the right decision for now.”
This is an extract from the 16 page feature in issue 21 of Hackspace magazine. To find out more about the Raspberry Pi 4 including an interview on the design process click here.
