Martin Cowen ⁽³²⁾

In the first post of this series on CRCs, I'm just going to clarify the terminology used. I am not going to cover the maths of how CRCs work in these posts, which can get surprisingly complex for what appears to be a set of simple bitwise manipulations and instead defer to Ben Eater's excellent CRC tutorial on YouTube. Small correction to the video, as noticed by commenter David W Smith, the length shown in Prof. Koopman's tables are in bits not bytes. They are for the dataword i.e. not including the FCS. I'm going to follow Prof. Koopman in his terminology Code Word is the whole message, with the payload being the dataword. Note that in this definition, any header is included in the Data Word. The Frame Check Sequence is the addition to the payload which adds redundancy and hence allows errors to be detected. It is an error code of a type given in Error Coding. The FCS must be after the data word to get the burst error detection benefits. Hamming distance (HD) is how many bits have to be changed to get from one valid codeword to another, as a minimum. This means that all…

Excel is a great all purpose tool, used by maybe 7% of the world's population. From shopping lists to budgets, Gantt charts and calendars to circuit simulators and digital music workstations, it can do it all. It is so good at so many things and so universally available to businesses that in many cases the biggest competition for software startups is not other specialized software solving the same problems but Excel. When it comes to using Excel for engineering tasks, there are lots of known pitfalls. Treating values as dates, or strings which are supposed to be hex like "51E67" as scientific format is one big category of pitfalls. Another is that although the probability of an error in any one cell is small, when you have a high number of cells all dependent on each other, the probability of error somewhere in the sheet means that the final result is likely to be wrong. The canonical case study is Reinhart and Rogoff, covered by a talk I highly recommend, Emery Berger's "Saving the World from Spreadsheets". So cross checking or auditing become necessary. Use CTRL-` to switch between formula view and value view. In common with many computer languages,…

I've been building up this set of equipment on my bench at home over the last few months, with some older kit reused. It's the minimum needed to do embedded development and I don't even have a bench power supply yet. I can get away without one since the dev kits are USB powered, but when I need one I have my eye on the Gophert NPS-1601 From top left to bottom right 1280 x 1024 @ 60 Hz VGA and DVI inputs, USB hub with 2 downstream USB-A. Was £360 in 2003. 13" 1920 x 1080 @ 60 Hz matte non-touch display Intel i5-5200 CPU @ 2.20GHz (Broadwell-U, 14nm, 2 cores, 4 threads) 8 GB DDR3 RAM, 256 GB SSD Liteon L8H-256V2G-11M.2 Intel HD Graphics 5500 Windows 10 Home USB3 Type A x2, Mini Display Port, 3.5mm phones/mic, SD Card slot Liteon disk results in AS SSD Benchmark 1.7 Read: Seq @ 514 MB/s, 4k @ 22 MB/s, Acc Time 0.12ms Write: Seq @ 225 MB/s, 4k @ 57 MB/s, Acc Time 0.08ms Review Reference Guide Full HD 1080p on DVI & VGA, 4k on HDMI Buy (Amazon) was £17 in 2021. Buy (Amazon) was £8 in 2016. 14…

Having got the BLE Lightbulb peripheral example working as I wanted it to on the nRF52 development kit (PCA10040), the next step was to get my other dev kit to be the controller for it, in place of the smartphone app. NovelBits helpfully provides all the code for this on the page How to build the simplest nRF52 BLE Central (Lightbulb use case) but it is targeted at the nRF52840 and SDK 15. I only had one nRF52 dev kit and one nRF51 dev kit. As I learned previously, the nRF51 is only supported by SDK version 12, so I had the job of porting the example code down from SDK version 15 and changing it over to the smaller, M0 based chip. At the same time, the Softdevice (BTLE stack) changes from s132 to s130. My plan was to proceed cautiously, having seen the problems previously in attempting to make many changes in one step and ending up with an uncompilable codebase. As soon as you copy the project folder into the same location in the SDK 12 folder and run my SES Include File Manager, you see that of the 133 include paths 29 are not found,…

SES Include File ManagerA simple helper application for use with Segger Embedded Studio when working with the Nordic Semiconductor SDK. The application checks which paths exist and allows you to remove those that don’t, allows a search by filename to show which folder they are in, and allows conversion between relative and absolute paths for the include folders. (It does not search your SDK folder for include files to automatically add them to the include paths.) The Nordic SDK folder is structured so that many include files which are needed for a project are in different folders. All of the folder paths need to be added to the c_user_include_directories definition for the project to compile. It is time consuming to search for each include file that a compile will complain about being missing so that it’s path can be added to the project c_user_include_directories. It is easy to end up with duplicate paths and unnecessary paths. The relative path can be tricky to manage due to its change of depth (number of ../) when a project is moved within the folder structure. Opens the file, parses it and shows the results in two lists - Include Paths and Include Files.