Replies: 2 comments 8 replies
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Only 32 channels can be accessed by the PIO, so is not double but a good increment. Said that, I have been already working in something for sometime... not an RP2350B but two interconnected RP2350B with synchronized clocks, a custom high speed intercom protocol and two high-speed SPI 4MB memories. Right now I have a ton of work in my daily job so I don't know when it will be ready, but it is already in process :) |
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I think the limitation is that only 32 channels can be accessed by ANY ONE PIO, but by using the GPIOBASE register, you can choose which 32, either 0-31 or 16-47. I don't know the specifics of your implementation, but I'm guessing that you use a single PIO. To make a 48 channel analyzer, you would probably have to use two PIOs. This may cause some limitations/complications in triggering, but considering the miracles you've already achieved, I have faith that you could solve them. In any case, you do you. You've already created a quite powerful product. BTW, back in 1985, I was a freshly graduated electrical engineer, and my first project was the redesign of a bit-slice processor. To get it working, I used a logic analyzer with something like 64+ channels. (That analyzer was in high demand, so I shifted my work schedule to come in at night, when it wasn't in use.) Based on that experience, I'll probably always scream for more channels. :-) Good luck with your current projects, both in your daily job and your "extra" job. |
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Yes that's correct, you can choose among two pin sets, but I don't think there is enough space in the PIO units for more programs (one PIO is used for the trigger and other for the capture, not all the SMs but nearly all the 32 instructions, the fast trigger alone if used eats a full PIO instruction space) and also the bus matrix would be oversaturated, doing two transfers each two clock cycles would leave literally zero cycles for the CPUs to execute anything and then, or the CPU gets blocked or more possible the DMAs get delayed and the captures would have glitches. I already do that for the blast mode and it took me a lot to get it to work properly, blocking everything while it is capturing, disabling all the IRQs, execute from RAM and pray for the CPU as being on a tight loop to use only cached instructions xD In any case, the one that I'm preparing is for 62 channels, and 62 is better than 48, right? 😄 |
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Let me check my math books . . . yes, it says right here that 62 > 48, so 62 is better. But if you're using two RP2350Bs, why not something close to 2x48 = 96? Just kidding, I'm excited to see your new design. |
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I'm going to use 10 GPIOs to intercomunicate the mcus, only one of them is going to act as master and be connected to the USB so the capture buffer and commands needs to go through the master and I'm going to send data between both parallely at 100Mhz, or at least that's the idea :) |
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Hello Dr. Gusmann. I've been away for a while, but I'm back. I'm really enjoying the tests I'm doing with LAC. Congratulations on the project's tremendous progress. https://github.com/WeActStudio/WeActStudio.RP2350BCoreBoard
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Hey! Yeah, I know these, in fact I have 4, they are pre-A4 but for the analyzer are the same, is one of the paths of investigation that I'm following for the next version :) |
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Ok, now I have a more bit of time to explain :) Yes, I know these, I bought four when I saw them, but they have some design flaws. Well, is not flaws but poor dessign choices. I checked where are the jumper resistor to remove it, and it is the one below the key and RST buttons, and to remote it is really going to be extremely hard for a lot of people, so this for me discards these boards. Said that, I found a better option:
This is basically a breakout but with the clock, voltage regulator, flash and PSRAM, nothing extra added, so it's perfect for the analyzer, the USB can be placed in the analyzer board, I can use the 32 channels and also have the other 16 channels for extra functionalities (and of course the PSRAM, I have been toying with these and after tweaking them I got up to 50Mb of speed writting, so they start to be in the useful range... 😄 ) So that's what I'm working on, I started before a design from scratch for 64 channels, but it's a very time demanding task and I don't have enough time to do all by myself, so I switched to these modules and that's what I'm working on right now, the idea is to have a 31 channel analyzer (yeah, not 32, still need the 1 GPIO for the triggers 😞 ) plus 8 output channels to reproduce signals, and even maybe protocol analyzers (RS232 inputs, SPI inputs, I2C inputs, etc). |
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@gusmanb these boards could be interesting as well - comes with or without PSRAM: https://www.olimex.com/Products/RaspberryPi/PICO/RP2350-PICO2-BB48/open-source-hardware |
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Too many connected GPIOs, the SDcard is connected with pull-ups, also led's and so on, that's why I find so interesting the Core2350B, it has zero "extra" stuff, just the minimal hardware to get it running and the rest is up to the device were you will use it :) |
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I'm totally impressed with the product as is. A 24 channel, up to 400 MHz logic analyzer for around $35 ... AMAZING!
But, of course, there are always possibilities for improvement. Have you thought about ditching the Pico or Pico 2 board and using the RP2350 chip directly? Apparently, there's a RP2350B QFN-80 version that has 48 GPIO pins - seems like that would be a fairly easy way to double the number of channels...
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