Responsiveness of microcomputer

[tomcer2003]

Hi, I'm building ecu for a bike, now I'm deciding between arduino deu(arm based), raspberry pi zero and raspberry pi 3B. I'm looking for 2ns response from input tu output. If I use raspberry I won't run Linux or any operating system, just a code for my needs, I know that system is makings higher latency. Sorry if this is in wrong forum section, but I didn't know, where to put it and as this is for software I thought it's good place here. 

[LogicalDrm]

-> Moved to Hobby Electronics

[stipuledfatcat]

On 1/8/2022 at 5:06 AM, tomcer2003 said:

Hi, I'm building ecu for a bike, now I'm deciding between arduino deu(arm based), raspberry pi zero and raspberry pi 3B. I'm looking for 2ns response from input tu output. If I use raspberry I won't run Linux or any operating system, just a code for my needs, I know that system is makings higher latency. Sorry if this is in wrong forum section, but I didn't know, where to put it and as this is for software I thought it's good place here. 

Short answer none of those based on my limited knowledge of ARM based stuff and slightly more knowledge of electronics.

Long answer:

Spoiler

2ns is a very quick response time, you would need a chip that runs at at least 500MHz to have a chance at achieving that kind of speed and that's assuming all the operations between input and output occur in 1 clock cycle. That is also ignoring the fall and rise times for the output and the delay for the output FETs.  Plus add in the delay between GPIO to processor and back to GPIO, you end up with a situation where you either need a more purpose built MPU/MCU, an FPGA, or fast switching discrete logic.

 

[tomcer2003]

On 1/16/2022 at 10:19 AM, stipuledfatcat said:

Short answer none of those based on my limited knowledge of ARM based stuff and slightly more knowledge of electronics.

Long answer:

  Hide contents

2ns is a very quick response time, you would need a chip that runs at at least 500MHz to have a chance at achieving that kind of speed and that's assuming all the operations between input and output occur in 1 clock cycle. That is also ignoring the fall and rise times for the output and the delay for the output FETs.  Plus add in the delay between GPIO to processor and back to GPIO, you end up with a situation where you either need a more purpose built MPU/MCU, an FPGA, or fast switching discrete logic.

 

sorry I ment 2 ms. Miss click 

It´s just for display readings and ignition modulation based on RPM. In future also for supporting fuel injection in carburator

[djneo]

2 ms should be fine for most Micro's
personally I would go for something like the AVR 328p, esp32 or the Due to get the required speed without having to deal with the complexer cpu of the Raspberry's and the boards limitations for use as a Real time mcu

Raspberry Pico might be an option as well or and ESP32 chip with FreeRTOS
 

[stipuledfatcat]

On 1/20/2022 at 9:36 AM, tomcer2003 said:

sorry I ment 2 ms. Miss click 

Well in that case probably most things, mostly its going to come down to IO and other features you want to have.

15 hours ago, djneo said:

2 ms should be fine for most Micro's
personally I would go for something like the AVR 328p, esp32 [...]

ESP32 is fairly solid, there are some good STM32 chips out there as well for a more barebones setup. I would say stick to 32bit MCUs if a small increase in cost and slightly higher potential power draw is not a concern as it gives you more flexibility for new and current features. Though from the description you gave (might not be the whole picture and don't know the design specs you are work with) you might be able to get away with an 8bit micro like the AVR or PIC family but you might end up scratching your head a bit more when coding up the firmware.

Good luck with the design