Cheapo logic analyser - Page 1
Forum section: electronics / testgear

author: PerranOak
author_rank: Frequent Contributor
timestamp: August 04, 2021, 10:42:04 am
content: I’d a logic analyser but don’t want to pay loads for it!I guess my best option is a PC based one?Does anyone have a recommendation for a real tight-wad? (Other than: “put your hand in your pocket you cheap@rse”)Cheers.

author: Fungus
author_rank: Super Contributor
timestamp: August 04, 2021, 10:53:59 am
content: What bandwidth?

author: tggzzz
author_rank: Super Contributor
timestamp: August 04, 2021, 11:03:54 am
content: You need to think about and tell us:what type of signals => threshold voltageshow many => widthprotection from high voltages, if appropriatedecoding quantised voltages into digital signals => protocol analysisminimum transient you need to capture => sampling rateignoring irrelevant detail => arm/trigger/filterstage machine or asynchronous => sampling speedand anything else so that we aren't playing "20 questions"

author: PaulAm
author_rank: Frequent Contributor
timestamp: August 04, 2021, 01:48:29 pm
content: If you can deal with the limitations you won't get anything cheaper than a Sileae clone. You can get an 8 bit version for under $10 USD. They work reasonably well with Sigrok.More lines, higher bandwidth, etc and the prices go up.

author: PerranOak
author_rank: Frequent Contributor
timestamp: August 07, 2021, 02:08:21 pm
content: Right. You've got me now.I would use it to decode I2C, UART and such on simple PIC projects (mostly 8-bit, I guess) and maybe the odd USB bit of USB. There will not be any really fast stuff (except USB) so something pretty Micky-Mouse will do.Cheers.

author: CJay
author_rank: Super Contributor
timestamp: August 07, 2021, 02:31:33 pm
content: Cheap as chips Cypress clone of the Saleae with Sigrok has done me proud when I've debugged I2C & slow (ish) SPI.Sigrok can be a bit flakey, so can the Cypress clone thing but for under a tenner I have absolutely zero grounds to complain, the messing about cost me far less than a 'proper' LA and the combo got me out of a hole on more than a few occasions.For that sort of money and most of your use case, it's got to be worth a go.You're going to need to shift some real money to deal with native USB

author: Fungus
author_rank: Super Contributor
timestamp: August 07, 2021, 04:10:40 pm
content: Quote from: PerranOak on August 07, 2021, 02:08:21 pm...apart from the "USB" part, which needs several GHz of bandwidth.

author: tggzzz
author_rank: Super Contributor
timestamp: August 07, 2021, 05:10:56 pm
content: Quote from: Fungus on August 07, 2021, 04:10:40 pm... raises non-trivial probing problems, and probably needs protocol decoding and packet level decodes.

author: DavidAlfa
author_rank: Super Contributor
timestamp: August 07, 2021, 05:46:19 pm
content: Search "24 mhz logic analyzer" in aliexpress/ebay/etc.For $6 you get 8-ch 24MHz sampling rate, no capture depth limits.Saleae logic analyzer software is superb, I actually find it better than sigrok, althought it doesn't support so many protocols.

author: alm
author_rank: Super Contributor
timestamp: August 07, 2021, 07:31:07 pm
content: Quote from: DavidAlfa on August 07, 2021, 05:46:19 pmNo surprise it's better, given that the Saleae software is commercial and only licensed to be used with their hardware. But since they didn't include any copy protection in their first generation of hardware, you'll be able to use their software with the cheap 'clones' as long as you ignore their license until they stop supporting their old hardware.

author: DavidAlfa
author_rank: Super Contributor
timestamp: August 07, 2021, 08:04:11 pm
content: I don't use it for working or anything like that. Purely for hobby use, fiddling around or learning. So the difference for them would be zero.

author: PerranOak
author_rank: Frequent Contributor
timestamp: August 09, 2021, 05:49:56 pm
content: Brill, cheers all.I think I'll leave the USB element for another time.