Links to all my PIC tips, tricks and 'mini-project' notes
Whilst the mid-range PIC's can tackle many complex and otherwise almost impossible applications with ease, the challenge is to minimise cost by using the cheapest baseline PIC 'whenever possible'. Baseline PIC's can be had for less than 50p each = I purchased many 16F5x chips for between 40 and 50p each (mainly from CPC as 'remaindered' stock in their 'Bargain bin' section).
The even cheaper to use 12F675 (it has an internal OSC) can be found for as little as 20p (in Qty 10pcs, eBay), as can many other PIC's for less than £1 each. These PIC's are so cheap that you will soon start using them 'for everything' (especially as the PIC can often be used in place of a higher cost 'single function' digital chip - such as divider, ADC, PWM generator etc.) !
Buying the PIC in a 'TSOP' package is (sometimes) cheaper than the DIL/DIP package version = and whilst this costs you 10-20p extra for a mini-PCB TSOP-DIP 'converter', if you use a 'bigger' PCB than the PIC TSOP really needs you can mount other devices (resistors, caps, even osc. crystals) on the same board - and make use of the extra 'pin holes' to wire this up to the rest of your circuit
Below is a mix of programming tips and tricks, common circuit tricks and all the 'mini-projects' I've used the PIC for
I hope these details proves as useful to you as it does to me !
Below, click on the '+' to expand 'in place' (includes diagrams/images) or click the title URL (to view/download the text only version).
(+) 0004 Multi byte ADD - (24bit)
(+) 0005 new PIC 33 instruction set - (macros)
(+) 0006 Binary multiply methods
(+) 0007 8x8 - (multiply)
(+) 0008 8x16 - (multiply)
(+) 0011 Bi color LED driving
(+) 0012 One pin dual LED and button detect
(+) 0013 Input only multi button detect
(+) 001a One pin controls motor Fwd off Reverse
(+) 001c One pin controls 3 relays
(+) 0020 I2C bit banging
(+) 0021 I2C code
(+) 0021 Serial link - (9600 baud)
(+) 0028 RS422 RS485 drive with one PIC pin
(+) 0030 D to A conversion - (R2R DAC)
(+) 0031 Ternary DAC - (R3R)
(+) 0032 Hybrid ternary bit conversion - (code)
(+) 0035 Pulse Width Modulation - (PWM)
(+) 0040 Gearing axis sensor
(+) 005a TYC50 AC motor details
(+) 0061 16F54 2char month map - (VTI)
(+) 0062 DDmmmYYYY character map - (VTI)
(+) 1000 PIC16F684 tips and tricks
(+) 2000 18Fx tips and tricks
(+) 6500 18Fxx data Table output - (max rate)
(+) 6501 18Fxx Return with value LUT - (max rate)
(+) 6502 18Fxx extended instruction data output - (max rate)
(+) 6530 simple data transmission
(-) 6540 Using RS485
RS485 uses twisted pair (A+, B-) signaling, just like RS422 (but, unlike RS422, it supports multiple 'masters' on the same bus), often with a ground (shield) wire (C). Full duplex uses 2 pairs, one for Tx the other for Rx, however bi-directional 'half-duplex' is supported over a single pair (so is more common, especially for long cable runs, which can be up to 1km !). Driver voltages are typically +/-2.5v to +/-5v (max +/-6v) = the minimium 'specified' reciever difference is +/- 1.5v however most work down to +/-200mV (the max. voltage, refernced to chip ground, on any pin is -7 to +12). 'Idle' state is usually A more positive than B (which is taken as a '1') and (since the drivers are 'tri-state', idle is 'guaratneed' with the use of 'bias' resistotrs). You can, in fact, 'get away with' using TTL 0,+5 and +5,0 as the two states
Termination
Ideally an RS485 system consists of a single linear cable (no branches) with 120 ohm resistors connected across the 2 wires at each end of the cable. RS485 can handle speeds of over 10 Mbits per second and line lengths of over 1 km. If you are operating anywhere near these values you must arrange your wiring close to the ideal. For many applications where baud rates are slow (say 9600 baud), and lines are only tens of meters long, this is not essential. The wiring requirements can then be relaxed to allow cables to run in star arrangement from the computer and the terminating resistors become optional.
Usage
RS485 is used for the 'Profibus' and 'Modbus' interface standards, and extensivly used for CCTV camera control (for example,
This note last modified: 3rd Jun 2017 05:06.