Memory Protections

Started by Don Y in comp.arch.embedded2 months ago 9 replies

Conceptually, memory (or a memory region) can be thought of as being readable, writeable or executable -- and any combination of these. ...

Conceptually, memory (or a memory region) can be thought of as being readable, writeable or executable -- and any combination of these. Hardware *may* enforce these protections -- to varying degrees. Usually, you opt to PREVENT some set of these operations (i.e., no write, no read, no execute). In many cases, this acts as an invariant -- "this is data; nothing should be mucking with it ...


My Favorite Editor is the Butterfly, What's Yours?

Started by Rick C in comp.arch.embedded2 months ago 16 replies

https://xkcd.com/378/ -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209

https://xkcd.com/378/ -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209


Page sizes

Started by Don Y in comp.arch.embedded3 months ago 40 replies

Are there any processors/PMMUs for which the following would be true (nonzero)? (pagesize - 1) & pagesize

Are there any processors/PMMUs for which the following would be true (nonzero)? (pagesize - 1) & pagesize


PID controller: dummy questions

Started by pozz in comp.arch.embedded3 months ago 27 replies

I'm trying to implement a PID controller in C for an embbeded system. This is the first time. I think I haven't fully understand the...

I'm trying to implement a PID controller in C for an embbeded system. This is the first time. I think I haven't fully understand the theory. For the proportional term, we have an output from PID controller that is P = Kp*err Suppose I have a power supply with a variable output voltage. The power supply output is connected to a low-value resistor that dissipates power and transfer...


NXP LPC 2468 interrupt vector checksum?

Started by Tauno Voipio in comp.arch.embedded3 months ago

The NXP LPC 2468 documentation states that, in order to start up, there must be a valid checksum over the interrupt vector in the start of the...

The NXP LPC 2468 documentation states that, in order to start up, there must be a valid checksum over the interrupt vector in the start of the Flash image. The document demands the the checksum over the vector must be zero. There are vague and contradictory statements what is counted as the interrupt vector. In ARM7TDMI documentation the vector is 8 words (32 bytes), but the NXP docu...


Tests in embedded

Started by pozz in comp.arch.embedded3 months ago 7 replies

I'm reading TDD book by Grenning, but I don't know if it is really up-to-date. Do you use unit tests, automatic testing and/or TDD approach...

I'm reading TDD book by Grenning, but I don't know if it is really up-to-date. Do you use unit tests, automatic testing and/or TDD approach in your embedded projects? Which tools do you really use? Writing some tests for isolated units is very simple, they can be manually written with some asserts. When the unit is connected to other units (i.e., uses services from another module or ...


Zephyr Project

Started by pozz in comp.arch.embedded4 months ago 4 replies

https://www.zephyrproject.org/ What do you think of this project? An open-source full-featured RTOS that runs on many dev boards with 32-bits...

https://www.zephyrproject.org/ What do you think of this project? An open-source full-featured RTOS that runs on many dev boards with 32-bits MCU/MPU, with or without memory protection. From the Linux Foundation. I didn't know it, until now.


e-Ink and other paper like displays

Started by Rick C in comp.arch.embedded4 months ago 13 replies

I have periodically reviewed the e-Ink market looking for usable products without a lot of experimentation. Most of what I find are displays...

I have periodically reviewed the e-Ink market looking for usable products without a lot of experimentation. Most of what I find are displays without driver boards, a few high priced combos of displays with separate driver boards, but few docs and very few displays an driver boards with some sort of docs and/or library support. The one thing that always seems to be missing is an ea


Cortex-M: share an int between two tasks

Started by pozz in comp.arch.embedded4 months ago 48 replies

I'm working on a Cortex-M4 MCU and using FreeRTOS. One task: uint32_t wait_period; while(1) { // make some things ...

I'm working on a Cortex-M4 MCU and using FreeRTOS. One task: uint32_t wait_period; while(1) { // make some things vTaskDelay(pdMS_TO_TICKS(wait_period)); } The following function can be called from another task: void set_waiting_period(uint32_t new_period) { wait_period = new_period; } In this case, is it needed to protect the access of the shared variable wait_pe...


Making more of the C standard library mandatory for freestanding implementations

Started by Philipp Klaus Krause in comp.arch.embedded5 months ago 41 replies

In C, most of the standard library is mandatory for hosted implementations only, not for freestadning implementations. Still, I see many...

In C, most of the standard library is mandatory for hosted implementations only, not for freestadning implementations. Still, I see many functions, such as memcpy() and abs() often used in programs for embedded systems, and see no obstacles to implementing them even on small systems. Should more of the standard library become mandatory for freestanding implementations? For string.h, I h...


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