Practical_Electronics-May_2019

Small, cheap and powerful – Part 1

T

his month, we go back to
basics, looking at Microchip’s
smallest and most feature-lim-
ited processor, the PIC10F200 family.
This is a tiny processor available in a
hobbyist-friendly eight-pin DIL package
or even a six-pin SMD (surface mount
device) part not much bigger than a
speck of dust, as can been seen in Fig.1.
In this series of articles, we will use
both types of packages. Example pro-
jects will be created on a range of board
types, from breadboard and Veroboard
to tiny PCBs using the SMD version.

Minimalist PIC features
So, what does this device consist of? It’s
offered in a range of packages, but we
will focus on the two hobbyist friend-
ly parts – the eight-pin PDIP (plastic
dual in line package) and the six-pin
surface mount, shown in Fig.1. Both
packages offer the same functionality

• on the eight-pin variant, two pins are
  not connected.
  These devices can operate between
  2.0V and 5.5V, which makes them ideal
  for use with two or three alkaline cells
  without the additional cost of a volt-
  age regulator. Current consumption
  is 250μA at 2.0V, up to 1mA at 5.5V.
  The processor runs at a fi xed frequen-
  cy of 4MHz derived from an internal
  RC (resistor-capacitor) oscillator. An
  RC oscillator is normally very inac-
  curate, but each device is calibrated
  during manufacture and a calibration

‘Wait’, I hear you say. ‘Is that all? What

about I^2 C bus, SPI bus, UART?’ All of

these functions can be implemented

using ‘bit bashing’ of pins. If the protocol

that runs above those interface require-

ments is not too demanding, then there

is a chance the PIC10F will be capable of

achieving them. Remember, if your needs

are greater, simply choose a more power-

ful processor. I once asked a Microchip

account manager how many processor

SKUs they had. He went away for a bit

and then came back saying, ‘I gave up at

17,000’. The PIC10F family simply rep-

resents the absolute lowest-cost options

available from them, and we are going

to push those limits – hard!

I^2 C and SPI bus communications are

serial protocols based on ‘handshakes’

between devices to pass data. They

do not rely on accurate clock signals

or accurate timing of each data bit.

UART communication, however, does.

With the calibration data provided by

Microchip during each device’s manu-

facture, the device’s clock can be set to

an accuracy of 1% – enough for UART

communication at reasonable speeds.

Given this addition, proved by Micro-

chip, the devices capabilities can be

considered to be:

correction value is programmed into

a word in Flash memory. It’s amazing

that they can afford the cost of bespoke

timing correction given the low cost of

the chip – such is the power and effi -

ciency of the automation machines used

during chip manufacturing.

The device has an active standby

mode – sleep – where it can remain in-

active with it’s processor clock turned

off, but can monitor for transitions on

GPIO input pins and wake immediately.

In this mode the processor consumes

just 200nA – a fi gure that is as close to

nothing as you can get!

The processor is offered in four var-

iants, or ‘SKU’ varieties, the standard

industry term. The features included

in each variant are shown in Table 1.

Of the four variants we will focus on

the PIC10F202; the most limited fea-

ture set, but with a little more memory

to give us some fl exibility. To summa-

rise, the capabilities of the processor

we are playing with are:

 512 words of code, 24 bytes of RAM

 Internal oscillator calibrated to 1%

 8-bit timer

 4 I/O pins

 Wake on pin change

 Very low power consumption

Mike Hibbett’s column for PIC project enlightenment and related topics

Fig.1. The PIC six-pin SMD package –
‘smart dust’!

Feature PIC10F200 PIC10F202 PIC10F204 PIC10F206

Maximum frequency of operation 4 4 4 4

Flash program memory 256 512 256 512

Data memory (bytes) 16 24 16 24

Timer module(s) TMR0 TMR0 TMR0 TMR0

Wake-up from sleep on pin change Ye s Ye s Ye s Ye s

Comparators 0 0 1 1

I/O pins 3 3 3 3

Input-only pins 1 1 1 1

Internal pull-ups Ye s Ye s Ye s Ye s

In-circuit serial programing Ye s Ye s Ye s Ye s

Number of instructions 33 33 33 33

Table 1. Feature sets of the PIC10F200 family