Anybody know of a 20pin SOIC microcontroller that has pin 1=VSS and pin 20=VCC? - Page 1
Forum section: electronics / general

author: ArcticGeek
author_rank: Regular Contributor
timestamp: October 13, 2015, 02:14:46 pm
content: Hi folks,I'm trying to reverse-engineer one of those cheap Chinese panel meters that you can buy off ebay for a few dollars. They use a small 20 pin microcontroller to do all the work, with pin 1 as ground and pin 20 as VCC. The top of the part has been sanded off, so I don't know what microcontroller it is. I've checked the Microchip PIC series and Atmel AVR series, and from what I can tell none of those parts have the correct VCC/VSS pinout. I've done a continuity check and pin 1 is the only pin that is connected to ground, and pin 20 is the only pin connected to VCC. Pins 14 and 15 of this micro are used as the 2 ADC inputs, as this particular panel meter can measure both voltage and current.Anybody know of a microcontroller that has pin 1=GND and pin 20=VCC in a 20 pin SOIC package? Cypress PSOC perhaps??

author: asgard20032
author_rank: Regular Contributor
timestamp: October 13, 2015, 02:50:48 pm
content: Some msp430 have pin 1 vcc and last pin vss. If not, its either a 8051 (pretty popular in cheap chinese thing, but even non made in china thing have them... its just so popular worldwide), or a small arm cortex.

author: Dielectric
author_rank: Regular Contributor
timestamp: October 13, 2015, 03:04:31 pm
content: I can't think of any PSoCs with the power pins at 1/20 like that, the PSoC1s are all corner-power and PSoC4 has a totally different power layout. Plus, they cost too much to be in anything cheap

author: nctnico
author_rank: Super Contributor
timestamp: October 13, 2015, 03:35:19 pm
content: I vote for Texas Instruments MSP430 as well.

author: asgard20032
author_rank: Regular Contributor
timestamp: October 13, 2015, 03:56:32 pm
content: I am skeptical about msp430. Normally, that micro-controller family is more premium than most 8 bit hobbyist use (like few cent to 1 dollar more expansive), so normally, msp430 should be rare on cheapo ebay item from china.

author: ArcticGeek
author_rank: Regular Contributor
timestamp: October 13, 2015, 03:59:55 pm
content: No, it doesn't appear to be a MSP430. I did a search on the TI website of all the 20 pin SOIC parts, and all of those parts have power/ground pins on pins 2 and 4.

author: kfitch42
author_rank: Frequent Contributor
timestamp: October 13, 2015, 04:16:32 pm
content: What other details do you have? E.g. 3.3V or 5V? Do some of the pins go directly to the LCD and/or LED display? If they go directly to an LCD that can help narrow things since you are looking for a micro with a built in LCD driver. If they go through a driver chip, make sure the "driver" isn't the actual micro, and your sanded chip is just an ADC. What does the display interface look like? Could the display be smart enough to do binary to 7-seg conversion? This could mean there is no real micro in the design at all.

author: Davesaudio
author_rank: Newbie
timestamp: October 13, 2015, 05:26:05 pm
content: Often Holtek

author: free_electron
author_rank: Super Contributor
timestamp: October 13, 2015, 05:30:39 pm
content: Holtek , STC or Nuvoton

author: Scrts
author_rank: Frequent Contributor
timestamp: October 13, 2015, 06:50:18 pm
content: Micros, that have power pins not adjacent to each other should be thrown away and not used. EMC noise of current is compensated on close power pins because of opposite flow.

author: nctnico
author_rank: Super Contributor
timestamp: October 13, 2015, 07:01:42 pm
content: MSP430 is so ultra low power that it doesn't matter.

author: amyk
author_rank: Super Contributor
timestamp: October 14, 2015, 02:51:52 am
content: SamsungS3F8S28/8S24, orS3F94C8/94C4? Incidentally, the latter isused in some Chinese hot-air stations, so we might have a match...

author: marcopolo
author_rank: Regular Contributor
timestamp: October 14, 2015, 11:52:12 am
content: Elan ?http://www.emc.com.tw/eng/index.asp

author: ArcticGeek
author_rank: Regular Contributor
timestamp: October 14, 2015, 12:58:16 pm
content: Kudos to Amyk....I think it may very well be the Samsung part. It turns out that the way they wired the multi-digit display lines up fairly nicely with the IO port assignment on that part, as well as the ADC inputs and power pins match up as well.Thanks to all for the help!

author: amyk
author_rank: Super Contributor
timestamp: October 15, 2015, 03:30:55 am
content: If anyone here runs a datasheet site - please add asearch by pinoutfeature!

author: ngohungcuong
author_rank: Newbie
timestamp: March 14, 2017, 01:56:53 am
content: SN8P2722. Pin 1 is GND, PIN 20 is VCC.

author: raspberrypi
author_rank: Frequent Contributor
timestamp: March 14, 2017, 02:55:00 am
content: A search on google seems to say is msp430.But I also found a similar question with this response:QuoteNow that person knows what they are talking about!

author: ebclr
author_rank: Super Contributor
timestamp: March 14, 2017, 03:27:39 am
content: http://www.st.com/content/ccc/resource/technical/document/datasheet/42/5a/27/87/ac/5a/44/88/DM00024550.pdf/files/DM00024550.pdf/jcr:content/translations/en.DM00024550.pdf

author: mariush
author_rank: Super Contributor
timestamp: March 14, 2017, 06:44:37 am
content: Some Holtek microcontrollers also have Vss and Vdd at pins 1 and 16 or 1 and 20Ex :HT66F002/HT66F0025/HT66F003/HT66F004HT66F002/HT66F0025/HT66F003/HT66F004 :http://www.holtek.com.tw/productdetail/-/vg/66F002_0025_003_004HT66F0172/HT66F0174 :http://www.holtek.com.tw/productdetail/-/vg/66F0172_0174

author: bson
author_rank: Unknown
timestamp: March 14, 2017, 06:44:06 pm
content: Quote from: nctnico on October 13, 2015, 07:01:42 pmAnd besides, when in a TSSOP package at pins 1 and 20 they're about one decoupling cap apart anyway...

author: BrianHG
author_rank: Super Contributor
timestamp: March 14, 2017, 07:55:56 pm
content: Ohhh boy.....Go to this page:http://www.microchip.com/ParamChartSearch/Chart.aspx?branchID=30048Select 20 pins, every single 8 bit MCU there has pin1 vdd, pin 20 vssoops, I just realized I got the 2 pins backwards. Well, if you just happened to measure the 2 pins backwards on your PCB, then use the link I have provided above...