Analyzing the uBlox LEA-M8T hardware

Hello all,

these days I am playing with a multiconstellation GNSS receiver, concretely the LEA-M8T from uBlox. When I integrate any hardware module into my system I usually look what is inside.

For their modules uBlox integrates the different subsystems into a single silicon device so it is not possible to make a deep analysis on the module, but some common sections can be identified.

 

The two main elements are easily appreaciated. The M8030-KA automotive grade SoC and a 16 MB dual/quad SPI NOR flash memory from Winbond containing the system firmware.

At the bottom right we can identify a 26 MHz TXCO oscillator for the RF synthesizer, with a noise guard ring and rounded by VIAs to GND with its decoupling cap outside the ring. Beside the oscillator we see an RTC Crystal for the core.

At the bottom left we have some antenna short detection circuitry.

Below the memory we can see the core supply ferrite-C filter connected to the output of the onchip DCDC. I appreciated that VCC and VCC_OUT pins of the module are exactly the same!! connected by a direct track!! Looking at the datasheet, the only note about VCC_OUT is to leave it open if not used. Curiously the external VCC is used to supply (decoupled) the NOR memory.
More decoupling caps on top and left to the uBlox SoC.
A C-ferrite-C pi filter at the RF output voltage.

The RF path is clear on the design, coming out from the 40th pin, a matching network formed by inductor, parallel cap and series cap, a SAW filter?, a DC blocking cap and the DC adding LC low pass filter.

Curiously they did not take too much care about the USB differential pair as they cross one VIA far away from the other. On the other hand the UART RX, TX pins were routed together. It is true that the module is tiny and there are not too much length but it is costless to do it right.

 

 

About the PCB technology, they used buried VIAs technology with VIA-on-pad and probably a 4 layer stackup (signal | GND | signal & PWR | GND).

Hope you may find the analysis useful and interesting. Do not hesitate about adding your comments.

 

See you in other analysis ;) 

Firmware and Software differences. Where is the line between them?

To differentiate Firmware from Software is always a discussion aspect when speaking in the embedded systems world.

Firstly I want to introduce another discussion: What is an embedded system? A mobile phone is an embedded system? what about a TV, tablets or a GPS navigator? what about a Raspberry Pi or Beaglebone?

Lets take a formal definition of an embedded system, for example from Wikipedia:

"An embedded system is a computer system with a dedicated function within a larger mechanical or electrical system, often with real-time computing constraints."

Well, I mostly agree with that definition, however I would say "computational" instead of "computer" as computers are nowadays more associated with personal computers, far away from the idea that an abacus is a formerly a computer, and neither I would not say "whithin a larger mechanical or electrical system" as there could be simple embedded systems that could work alone, e.g. an alarm or a podometer.

It is true that the concept of an embedded system nowadays is actually diffused, mainly because some devices that previously were just embedded systems, today they are not. The best example is the mobile phone. The Nokia 3310 was an embedded system as the final user could only do limited functions with it: to call, to write a SMS, play to Snake... But now a mobile phone in fact is not an embedded system as it can do unlimited functions. You can install a new app and use it with a totally new function, like control you home lights or prepare some slides for a presentation, in the same way that you do with your - general - computer. This is why they are formerly known as smartphones, being not the same as a mobile phone.

In that way, answering to the devices presented, a GPS navigator is an embedded system, either a TV while a smart TV is not, neither a tablet. What about the Raspberry Pi? Good question: it depends on the targeted final user. Raspberry Pi was created to be used as a - cheap - personal computer with the main purpose of teaching programming, it has a general operative system where you can install different software, in the same way that you do with a smartphone.

The answer about the difference between Firmware and Software is the same: it depends. But in what?

Lets search the definition of Firmware, again from Wikipedia:

"In electronic systems and computing, firmware is a type of software that provides control, monitoring and data manipulation of engineered products and systems. Typical examples of devices containing firmware are embedded systems (such as traffic lights, consumer appliances, remote controls and digital watches), computers, computer peripherals, mobile phones, and digital cameras. The firmware contained in these devices provides the low-level control program for the device."

Uh, fine, wait... but where is the line between that "low-level control program" and the high level? An operative system is below or above that line? All code contained in an embedded system is just Firmware? Or maybe there are no firmware in a general use computer?

After some years I would stablish the following dependences which defines Firmware:

  • Firmware is commonly not to be changed by the final user.
  • Firmware is developed for an specific hardware and commonly it does not work if you load it into another hardware.
  • Firmware is always contained in a non volatile memory.
  • Software depends on Firmware in the same way that Firmware depends on Hardware.

Ok, then it is clear that the code developed for a remote control or traffic lights is just firmware and the code for any Android app is software as I can develop it knowing nothing about the hardware. But do not fall into the trap, it not depends on if code is done for an embedded system or not. In that way there would not be any software in an embedded system and in fact there is, alike there is firmware contained in a personal computer

In a personal computer, the FSBL (first stage bootloader) is just firmware, but a personal computer operative system is mainly software as you can replace, update or reinstall it. The most compromising aspect may be the device drivers contained in the OS, as the final user can replace or uninstall them, but in fact it should not be the common way (look at MACs, have you replaced manually and consciously any device driver?). In fact the same happens with the computer FSBL or BIOS.

Commonly is told that an embedded system only contains Firmware, but in fact nearly always there is a Firmware layer supporting the software.

Syndicate content