Low Price PIC's  from RS Components - Page 1
Forum section: electronics / beginners

author: neko efecktz
author_rank: Regular Contributor
timestamp: June 29, 2016, 04:29:48 am
content: Hi GuysI'm a newbie to micro controllers and have only built 2 test projects and don't have a lot of experience in selecting chips.I currently have a couple of PIC16F84A and need at least one more full port 0-7 for inputs.I am looking for some larger than 18 pin chips and found that RS Components in Sydney have over 1300 to choose from under $5.00 each.many of those are single or multiples of the came chip ie. 5 off 25 off etc and package type.I have attached a PDF file of a few that I am interested in.I am building a 2 x 16 LCD display with as many inputs as I can get from the chip of choice.The 40 pin chip would be great if it is ok.There are a few others as well.It will have digital and analog inputs and perhaps a digital output to trigger an alarm.Has anyone had experience with the chips in the list in a project similar to the one I have outlined.Thank you in advanceBill

author: kripton2035
author_rank: Super Contributor
timestamp: June 29, 2016, 05:54:07 am
content: you can't be wrong with a 16F877... even if it's an old chip !first chip that comes to mind if you want to upgrade a 16f84...then you will go to pic18

author: CJay
author_rank: Super Contributor
timestamp: June 29, 2016, 09:30:19 am
content: Quote from: kripton2035 on June 29, 2016, 05:54:07 amYep, I'd say that's the logical step forward, or at least one logical step. I kinda bypassed that one and went to 18F almost directly from the 'F84, the 18F4550, which is pretty much pin compatible with 'F877 and the 18F1330 which is again pretty much pin compatible with 'F84

author: Ian.M
author_rank: Super Contributor
timestamp: June 29, 2016, 11:35:25 am
content: Madness - Microchip tend to jack up the prices of older parts and the PIC16F877 is rather old, so you would be paying over the odds for an inferior chip.Assuming you are coding in assembler and you want to stay with the same midrange architecture, your best bet would be the PIC16F88x series, '887 for a maxed out 40 pin device and '886 for 28 pin.If you are coding in C or other high level language, the architecture is far less important, and its worth looking at the Enhanced Midrange PIC16F1xxx devices, or for a feature-rich PIC18 that can run at 5V, look at the PIC18FxxK22 device families.Avoid chips with built-in USB SIE (e.g PIC18F4550) unless you are implementing a USB device - the SIE takes up I/O pins, limits the clock options, competes with other peripherals for die space and pushes the price up, with no advantage to you if you aren't using the USB interface.Edit: corrected recommendation for midrange to '88x family

author: ebclr
author_rank: Super Contributor
timestamp: June 29, 2016, 11:50:24 am
content: One possible option with a price of 0.33USD8 Kbyte Flash, 128 byte data EEPROM, 10-bit ADC, 3 timers, UART, SPI, I²Chttps://world.taobao.com/item/45016812512.htm?spm=a312a.7700714.0.0.wsSczj#detail

author: Unknown
author_rank: Unknown
timestamp: June 29, 2016, 11:53:20 am
content: Microchip has search tools for their products which may be of help in narrowing down your choice based on what features are important to you or of interest to you.e.g.http://www.microchip.com/paramChartSearch/chart.aspx?branchID=1005I second the view to stay away from old legacy parts, they remain popular because they feature in old tutorials / books and projects but it is relatively trivial to port the designs over to newer parts.

author: luxfx
author_rank: Contributor
timestamp: June 29, 2016, 07:01:26 pm
content: What about using a shift register or GPIO extender? It could add some complexity to the code, but gives the benefit of adding plenty of inputs, potentially even chaining and getting even more.

author: KL27x
author_rank: Super Contributor
timestamp: June 30, 2016, 01:04:18 am
content: QuoteThere is no appreciable difference in architecture between 16f84A an 16F1xxx chips as far as user is concerned. A few new instructions were added which aid in C compatability, and they are also useful for coding in assembly. But you don't need to learn/use them if you don't want to. The enhanced midrange 1xxx chips have more peripherals (and/or more options to use those peripherals), low quiescent current, lower minimum supply voltage, linear relative memory addressing spanning all blocks, and an onboard PLL. And better pricing. But as far as assembly is concerned, there is no change. If you don't want to learn/use the few new instructions, then you don't have to. The only practical difference I have experienced is that "movfw [register address]" is no longer a valid instruction and must be changed to "movf [register address],w/0" (which has always been a valid alternative, so it is backward compatible). Other than that, porting a preexisting project from midrange to enhanced midrange is no different than changing between any other chip. For enhanced midrange, you don't need to do a darn thing different except pay less and get more.So I would definitely drop 16F88x and 16f877 off the list, unless you want to use one for a tutorial or something. If you want to use 8 bit PIC, might as well use the enhanced midrange. It's pretty much the same thing except better and cheaper. It's the 18F/24F where the architectural differences turn assembly into a nightmare.

author: batteksystem
author_rank: Regular Contributor
timestamp: June 30, 2016, 01:11:24 am
content: Quote from: neko efecktz on June 29, 2016, 04:29:48 amFor Beginner I would suggest PIC18F4520, you can't go wrong with internal RC and more than 4 ports of pins to use.

author: KL27x
author_rank: Super Contributor
timestamp: June 30, 2016, 06:04:47 am
content: ^ $4.26 each?Migrating from 16F84A, there will be minimal change if you stick with 16F. Just change your port addressing and config bits, and memory assignments, and the code will run. Also, "low price" being in the title of the thread:40 pin : 16F1937. $1.76 per64 pin : 16F1527. $1.76 per18F will generally be more efficient/capable if using a C compiler. But then 24F is probably even better for the $. 18F is sort of a niche where you want lower than 40 pin count and need the extra memory and moderately increased efficiency of C compiled firmware over 16F, IMO. BTW, if anyone has a project for 4k pieces of 18F4550, it's your lucky day. I can provide them for 20 cents on the dollar.