Cheap logic analyser? - Page 1
Forum section: electronics / beginners

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 14, 2021, 03:05:59 pm
content: My DHT11 is showing nan when I read it. I looked at cheap logic analyzers though I'm not sure it's something I really need (at some point I do want to try to program I2C etc). I found a couple of cheap options; are they worth considering or so cheap I should just buy a new sensor and be done with it?https://abra-electronics.com/test-equipment-tools/test-instruments/logic-analyzers/t-la-24m8ch-virtual-oscilloscope-logic-analyzer-module-8-channel-24mhz.htmlhttps://abra-electronics.com/test-equipment-tools/test-instruments/logic-analyzers/lht00su1-virtual-oscilloscope-logic-analyzer-data-logger-frequency-generator.html

author: fourfathom
author_rank: Super Contributor
timestamp: March 14, 2021, 03:20:21 pm
content: The cheaper of those two looks identical to this one I got via Amazon:https://www.amazon.com/gp/product/B077LSG5P2. Using this and the Sigrok "Pulseview" software (https://sigrok.org/wiki/Downloads) I've been able to monitor and debug I2C and SPI interfaces.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 14, 2021, 03:23:10 pm
content: Interesting. Did you have to buy anything else to use it, or does it come with everything you need? I.e. did you have to throw away the cables?

author: madires
author_rank: Super Contributor
timestamp: March 14, 2021, 03:26:21 pm
content: Those LAs are Saleae clones and ideal for tinkering with small MCUs. In most cases you can use the original Saleae software or PulseView (sigrok:https://sigrok.org) which is open source.Edit: And buy some mini-grabbers.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 14, 2021, 03:45:17 pm
content: Quote from: madires on March 14, 2021, 03:26:21 pmGood point, thanks!https://abra-electronics.com/test-equipment-tools/test-clips-leads-banana-posts/generic-low-cost/test-210-minigrabber-set-10-hooks-to-female-headers-for-logic-analyzer-testing.html

author: RoGeorge
author_rank: Super Contributor
timestamp: March 14, 2021, 03:48:23 pm
content: You can use use sigrok with whatever device you may already have (see the supported hardware listhttps://sigrok.org/wiki/Supported_hardware).A simple Arduino or any other microcontroller devboard, or maybe a Raspberry Pi, or any other SBC (Single Board Controller) will do it, too. My wild guess is even a soundcard can record the communication.A logic analyzer won't tell you much, and the DHT11 sensors are dirt cheap anyway, less than $1 on ebay or Aliexpress. Just replace it.The humidity sensor tends to dry out over time, so it should be looked as a consumable, replacing the sensor won't hurt (has a gel that absorbs moist from the surrounding air, thus changing its resistance and measure the humidity level, and that gel dries after a few years).

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 14, 2021, 04:00:07 pm
content: Good point. The DHT11 is about C$4 in Canada, but if it has a short lifespan, maybe I'll try to source a temperature sensor without a built in humidity sensor instead.I may still pick up the logic analyzer, as it's less than C$20, and will be useful tool for learning I2C.Thanks

author: Ian.M
author_rank: Super Contributor
timestamp: March 14, 2021, 04:07:45 pm
content: The supplied female-female Dupont wires supplied with most Cypress FX2 based Salae Logic 8 clones are usually somewhat adequate. If you are unlucky you may need to replace them.However if you get one that comes with mini-grabbers as well (or even buy cheap mini-grabbers separately) they are usually totally crap and require significant work to either permanently attach them to wires with female Dupont connectors on the other end, or add single header pins so they can mate with the existing f-f wires. A set of good quality grabbers will cost you more than the logic analyser!See my Amazon review:https://www.amazon.co.uk/gp/customer-reviews/R24R200YC0CCTVwhich was written before I thought of copper flash-plating the grabber tabs to make them solderable:https://www.eevblog.com/forum/beginners/soldering-to-strange-metal-contacts/msg3315492/#msg3315492I've attached a (zipped) session setup file for Sigrok Pulseview, which names the channels as per the label on the logic 8 clone, and colors them to match the ribbon cable.Caution: some Logic 8 clones have a 'CLK' pin rather than a second ground pin. Its *NOT* a sampling clock input as would be found on 'classic' standalone logic analyzers. Instead its CLKOUT from the Cypress FX2 MCU, and is likely to be 48MHz, (though different firmware can set a limited selection of clock divisors resulting in 24MHz or 12MHz), so is essentially useless unless you are using the logic analyser as a USB interface for external sampling or ADC hardware that requires a clock.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 14, 2021, 06:32:30 pm
content: Thanks Ian. That's a scathing review. Is there an alternative you would recommend?

author: Ian.M
author_rank: Super Contributor
timestamp: March 14, 2021, 07:39:29 pm
content: Don't get me wrong - I'm entirely happy with the logic analyser itself, but *DON'T* pay any premium to get extra bundled accessories as the odds of them being better than marginally usable are close to zero.AFAIK there is nothing at the same price-point as the Logic 8 clones that's even half as capable, so simply go ahead and get the best deal on one from any supplier that has a good returns policy, pop it open and check the soldering under a magnifier and test all the channels (you can easily write an Arduino pattern generator sketch), as soon as you get it.You've got my notes on copper flash-plating the steel tab of cheap mini/micro grabbers to make them easy to solder. If you are working with DIP package ICs test clips for the package sizes you use with 0.64 mm square*pins that will directly accept 'dupont' F-F wires are very useful. If you do a lot of breadboarding or Arduino stuff, get some reasonable quality 'dupont' M-F wires. Beware of cheap&nasty ones made of CCA or CCS wire or with badly crimped ends. Check mid-span with a magnet to eliminate CCS wire, tug test the ends and check the resistance is 'in the ballpark' for copper wire of that length and (estimated) wire gauge, or at least is lower than you can accurately measure, so you can return crap promptly. Suppliers with a physical 'bricks & mortar' presence in your country/region are somewhat less likely to try to bilk you vs internet sellers of no particular reputation.N.B. DuPont was the original manufacturer of cable mount male and female contacts and shells for 0.1" pitch headers. They sold off their connector division a long time ago. Seehttps://www.eevblog.com/forum/chat/dupont-connectors/* 0.64mm/0.025" square is the standard 0.1" pitch header pin size

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 14, 2021, 07:40:03 pm
content: Another option is this:https://www.amazon.ca/Akozon-Generator-Oscilloscope-Multi-Function-Oscilliscope/dp/B07HT5ZS5Z/I recall watching a video on this one, so I'll re-watch that to see what they said about it.

author: WattsThat
author_rank: Frequent Contributor
timestamp: March 15, 2021, 05:22:32 am
content: If you’re patient, you can find original HP mini-grabbers for about $1 US each on eBay. Easy to find at $2 each and up. Search for HP 5090-4356. The only downside is that standard 0.1 DuPont female sockets don’t fit, the plastic housings are too large. The solution is easy, remove the housing and insulate the connector with heat shrink tubing.They’re far superior to any of the “imported” products. They fit nicely on SOIC pins and smaller. Just be careful, whacking them with just about anything will bend the claws. They can be repaired with very small flat jaw pliers but they never hold as well as new ones.

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: March 18, 2021, 12:32:41 pm
content: I picked up one of the cheapest logic analyzers. I only had time to verify I can use it to see rising and falling edges from a PIR sensor. I haven't hooked it up to anything using I2C yet. At least now I know how to use the basics of the software (both Logic and PulseView).

author: GodIsRealUnless DefinedInt
author_rank: Contributor
timestamp: March 18, 2021, 05:14:10 pm
content: You don't want to pay more than $8 or $9 for the 24MHz / 8 Channel one. They will do you fine up through the start of the USB data rates of you want to use it outside of standard microcontroller. More expensive units are not going to buy you much, the more channels the slower the upper limit per channel when they stream across USB to your PC so all you get for more money is faster upper limits but still limited to just 2 or 4 probes at that speed and any more channels being sampled you once again get lowered max sample rates across all channels in use. Your next step up is about $90 from Aliexpress or $149 direct from official store. That gets you an FPGA based unit to handle more channels at higher sampling rates plus you start getting inboard memory so you can sample direct to inboard ram for fastest speeds but limited capture length by ram size. All that really buys you outside of those two features is being able to handle USB 2 full speed data rates with ease over the cheapest unit which gets you to USB 2 low speed data rates. Chasing speed the probes become an issue just like with oscilloscopes as those fly wires can do nasty things to your DUT and signals. I would recommend buy the cheapest one but at $8/$9 and a decent set of clips (E-Z-Hook) or get some of the better ones from Aliexpress. Attached is a photo of my Chinese probes, the ones in your listing ar gargantuan in comparison but OK for through hole electronic components like you have with Arduino so they will suit fine. Those huge probes with the cheap unit you just pull thr plastic end off and there usually is a solder ring on the inside. You take the female dupont cables and cut one female connector odd and solder the wire end to the ring and then you have assembled the probe kit for that cheapest LA unit. The cheapest unit has no firmware, that gets sent to the chip when the USB is connected and the driver loads firmware onto the chip to make it perform as required for logic analyzer use. With Sigrok you get a fully open source driver that will download into the unit so you get all the functionality of the discontinued Saelae unit without worry about using their IP which definitely isn't the hardware side of the LA as the chip manufacturer publishes information on how to use their chip as a LA which is the same as Saelae and these Chinese units hardware.But check out the size of my Chinese probes for comparison to the onea you get bundled with the cheapest units.

author: mattselectronics
author_rank: Contributor
timestamp: March 19, 2021, 12:03:15 am
content: I got one that looks exactly like the cheaper one for about 3€ a few years ago.They are clones of the original saleae and they also had the right IDs configured, so logic detects them as such.I like Logic and so I got the real deal (Logic 8 ) a while back and it is great!It also has an analog view (yes with ADCs, max 10MS/s), which made me realize some issues much faster than a pure logic analyzer would have.There is a program where they hand out discount codes for hobbyists.https://blog.saleae.com/saleae-discounts/They sent me discount codes for all versions, not only the Logic 8.

author: Gyro
author_rank: Super Contributor
timestamp: March 19, 2021, 09:55:18 am
content: Nice products but unfortunately ~$400 for 8 channels 100Msps digital / 10Msps (1MHz) analogue takes them out of the cheap category.

author: mattselectronics
author_rank: Contributor
timestamp: March 21, 2021, 12:46:35 am
content: My Logic 8 (without Pro) was with the discount code 208€ incl. VAT and shipping.Of course that's not super cheap, but I think pretty reasonable and you have the real product and not a cheap Chinese knock off.

author: solhuebner
author_rank: Newbie
timestamp: March 21, 2021, 03:35:47 am
content: Quote from: madires on March 14, 2021, 03:26:21 pmMy one looks slightly different (but they just come with different stickers) and is working fine so far. The Saleae software "Logic" just got revamped with some kind of in-app "marketplace" with free Python extensions. Might be worth a look if you are missing something in Sigrok.