HOW-TO: THE BUS PIRATE, universal SERIAL interface

UPDATE: new firmware with JTAG and more

We’re always ecstatic to get a new chip or SIM card to interface, but our enthusiasm is typically dampened by the prototyping process. Interfacing any chip normally indicates breadboarding a circuit, writing code, and hauling out the programmer; maybe even a prototyping PCB.

A few years ago we built the first ‘Bus Pirate’, a universal bus interface that talks to a lot of chips from a PC serial terminal. several conventional serial protocols are supported at 3.3-5volts, including I2C, SPI, and asynchronous serial. additional ‘raw’ 2- and 3- wire libraries can interface nearly any proprietary serial protocols. considering that this has been such a beneficial tool for us, we cleaned up the code, documented the design, and released it here with specs, schematic, and source code.

Concept Overview

The Bus Pirate is a serial terminal bridge to multiple IC interface protocols. We type commands into a serial terminal on the computer. The commands go to the Bus Pirate through the PC serial port. The Bus Pirate talks to a microchip in the proper protocol, and returns the results to the PC.

All pins output 3.3volts, but are 5volt tolerant. On-board 3.3volt and 5volt power supplies are available to power the connected chip. software configurable I2C pull-up resistors complete the package.

The serial terminal interface works with any system: PC, Mac, Linux, palm Pilots, WinCE devices, etc; no crapware required. We considered a USB device, but USB isn’t compatible with the substantial number of hand-held devices that have a serial port. We also wanted a 3.3volt device with 5volt tolerant inputs, but a lot of popular through-hole USB microcontollers were 5volt parts (e.g. the PIC18Fx550).

The Bus Pirate currently ‘speaks’ three hardware protocols for high-speed interfacing, and has two software protocol libraries for easy bus manipulation. The theory and specification of each protocol is beyond what we can cover here, but check out some of these tutorials:

I2C

A slow 2 wire bus. Wikipedia is a terrific place to start for I2C background. I2C-Bus.org, Robot Electronics, Embedded Systems Academy, and Embedded.com have respectable I2C tutorials.

SPI

A basic 3 wire bus. Wikipedia has background; Embedded.com has a terrific tutorial and comparison to I2C.

Universal Asynchronous Receiver Transmitter (UART or serial)

A clock and timing dependent serial protocol best known for its appearance as the PC serial port protocol. Wikipedia has background on asynchronous serial protocols.

Raw 2 wire

This is a generic 2 wire protocol library, similar to I2C but without an ACK bit. I2C and lots of proprietary 2 wire protocols can be formed using the bus manipulations available in this mode. use this library to work with non-I2C 2 wire devices, like smartcards or Sensirion SHT11 temperature/humidity sensors.

Raw 3 wire

This is a generic 3 wire protocol library, similar to SPI but without the constraints of a hardware module. use this library to work with devices that use non-8bit compatible 3-wire protocols, like the Sparkfun Nokia 6100 LCD knock-off. lots of 3 wire protocols can be formed using the bus manipulations available in this mode.

Hardware.

Click for a full size PCB placement image (PNG). Screw terminals connect to the power supplies. A row of seven pin headers connect to the IO pins. despite the label, only 7volts DC is required.

PIN

SPI

I2C

RS232

B9

MOSI

SDA.

Rede –

B8

CLK

SCL

Rede –

B7

MISO

Rede –

RX

B6

Cs.

Rede –

TX

B5

AUX

AUX

AUX

Jord

GND

GND

GND

This table shows the pin connections for each bus mode. Raw 2 wire mode uses the same pin configuration as I2C. Raw 3 wire mode uses the same pin configuration as SPI.

Click for a full size circuit image (PNG). The circuit and PCB are created using the freeware version of Cadsoft Eagle. download the project archive (ZIP).

PIC 24FJ64GA002

We used a PIC24FJ64GA002 microcontroller in the Bus Pirate; this is the same chip we used in our mini-server project. It’s fast enough to do everything we want (16MIPS), and the peripheral pin select feature allows the hardware SPI, UART, and I2C modules to share output pins. Each power pin needs a decoupling capacitor(C12,13), and the MCLR function requires a resistor (R7) between pin 1 and 3.3volts. The photo has an internal voltage regulator that requires a 10uF tantalum capacitor (C3), though we used a plain electrolytic capacitor without issue. read about programming and working with this chip in our PIC24F tutorial. If you don’t have a photo debugger, several readers recommend the under-$40 ICD2 clones on eBay.

The photo runs at 3.3volts, but the digital-only pins are 5volt tolerant for interfacing 5volt logic. Pins 14,15,16,17,18,21, and 22, are digital only, which we figured out by looking through the datasheet and eliminating any pins with an analog connection type (table 1-2, pages 11-16). According to the datasheet,I2C pins are also 5volt tolerant. There’s a bunch of conflicting information on the web, but datasheet page 230, parameter DI28, clearly states that the max input for a 24FJ64GA002 I2C pin without analog circuitry is 5.5volts.

Pins 21 and 22 (RB10/11) can pull-up SDA/SCL through resistors R4 and R5.

MAX3223CPP

This chip converts 3.3volt serial output to +/-10volt RS232 signals compatible with a PC serial port. The MAX3223CPP is a 3-5volt version of the MAX202, with extra power saving features. MAX RS232 transceivers require four 0.1uF capacitors for a charge pump (C4,5,7,8), and one decoupling capacitor (C17). We used the same capacitors for everything.

We used a MAX3223CPP, which doesn’t seem to be available anymore. MAX3223EEPP+ is a pin-compatible newer version, available at Digikey for $7. Av! None of the 3223’s power saving features are used, so a cheaper, simpler 3.3volt RS232 transceiver must be substituted if in any way possible.

Strømforsyninger

Most chips can be powered from the Bus Pirate’s on-board 3.3volt and 5volt supplies. 5volts is supplied by a common 7805 regulator (VR2) and two decoupling capacitors (C9,10). An LM317 adjustable regulator (VR1) is set to 3.3volts using two resistors (R2,3), and requires two decoupling capacitors (C6,7). The circuit requires a 7-10volt DC supply (J1).

Delliste

En del
Værdi

IC1.
PIC24FJ64GA002-DIP

IC2.
MAX3223CPP (try MAX3223EEPP+)

C3
10uF capacitor (preferably tantalum)

C4-13,17
0.1uF capacitors

R1.
330 ohm resistor

R2
240 ohm resistor

R3
390 ohm resistor

R4,5,7
2K2 ohm resistor

Vr1.
LM317

VR2.
LM7805

X1
Screw clamp (3 terminals) *untested

X2
DB9 female connector (serial port) *untested

ICSP,SV3
.1″ pin header, ideal angle

J1.
Power jack, 2.1mm pin

LED1
3mm LED (optional)

Firmware.

Firmware er skrevet i C ved hjælp af den gratis demonstrationsversion af billedet C30 compiler. Lær alt om at arbejde med dette billede i vores introduktion til billedet 24f serien. download the project archive (ZIP).

main.c – Handles the user terminal interface.

busPirate.c – Abstraction routines that convert syntax to actions on the proper bus.

uartIO.c – IO routines for both hardware UARTs.

m_i2c_1.c – software I2C routines by [Michael Pearce]. We couldn’t get the photo hardware I2C to work, so we used this valuable library. The software doesn’t take into account the I2C speed setting, and seems to work at about 5KHz.

SPI.c – routines that drive the hardware SPI module.

raw2wire.c – software 2-wire interface library.

raw3wire.c – software 3-wire (SPI) interface library.

User input is held in a 4000 byte buffer until a newline character (enter) is detected. If the first character of the input is a menu option (see below), the menu dialog is shown, otherwise the string is parsed for data to send over the bus (see syntax). The code consists of an embarrassing number of switch statements and spaghetti code.

Terminal interface

Rather than write a junk piece of software to control the device, we gave it a serial command line interface that will work with any ASCII terminal.  The bus pirate responds to commands with three digit result codes and a short message. The codes are created with PC automation in mind. We’ve included a table of result codes in the project archive (zip).

Menu options

Menu options are single character commands that don’t involve data transfers. enter the character, followed by , to access the menu.

? – show a help menu with commands and syntax.

M – set the bus mode (SPI, I2C, UART, raw 2 wire, raw 3 wire). followed right away by a prompt for speed, polarity, and output state (mode dependent).

Bus speeds: SPI:30, 125, 250, 1000KHz. I2C:100, 400, 1000KHz. UART: 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200bps. Raw modes: 1, 10, 50KHz.

Inverse clock setting sets the idle state opposite of normal (normal SPI:idle low; normal UART:idle high): SPI:idle high; UART:idle low.

Some modes have optional high-z output modes for use with pull-up resistors (Low=ground, High=input).

L – Toggle bit transmit/receive order: most/least significant bit first.

P – SDA/SCL pin pull-up resistor toggle (3.3volts). only valid in I2C and raw 2 wire modes.

O – set number output display format. The terminal can display numbers as decimal, hexadecimal, and binary ASCII values. A fourth format sends the raw, unprocessed byte for reading ASCII formatted text.

Syntax

A basic syntax is used to communicate with chips over a bus.  Syntax commands have generic functions that normally apply to all bus types.

A/a/@ – Toggle auxiliary pin. capital “A” sets AUX high, small “a” sets to ground. @ sets aux to input (high impedance mode) and reads the pin value.

[ – start data write. SPI/raw 3 wire: chip select enabled. I2C/raw 2 wire: start condition. RS232: open UART, discard received bytes.

{ – start data write with reads. same as [, except: SPI/raw 3 wire: show the read byte for each write. RS232: display data as it arrives asynchroittly.

] eller} – Afslut data skriv. SPI / RAW 3 Wire: Chip Vælg deaktiveret. I2C / RAW 2 Wire: Stop tilstand. RS232: Luk UART.

R / R – Læs byte. SPI / RAW 3 Wire: Send Dummy Byte, returlæse. I2C: Læs byte med ACK. RAW 2 Wire: Læs 8 bits. RS232: Kontroller UART for byte og returnere, eller fejl hvis tom. Brug 0R1 … 255 for bulk læser op til 255 byte.

0b – Skriv denne binære værdi. Format er 0B00000000 for en byte, men partielle bytes er også fint: 0B1001.

0h eller 0x – skriv denne hex værdi. Format er 0H01 eller 0x01. Delvis bytes er fint: 0xa. A-F kan være små bogstaver eller store bogstaver.

0-255 – Skriv denne decimalværdi. Ethvert tal, der ikke er forud for 0x, 0h, eller 0b, fortolkes som en decimalværdi.

eller rum – værdi afgræns. Brug en koma eller plads til at adskille tal. Enhver kombination er fint, ingen afgrænsning er påkrævet mellem ikke-tal-værdier: {0xA6,0, 0 16 5 0B111 0HAF}.

Direkte busmanipulationskommandoer til RAW 2 Wire-tilstand og RAW 3 wire-tilstand.
^ – Send et ur tick. Brug 0 ^ 1 … 255 for flere klokkeoverskrydninger.

/ og \ – Skift urniveau højt (/) og lav (\). Inkluderer urforsinkelse (100US).

– / _ – Skift datatilstand Høj (-) og lav (_). Inkluderer data setup forsinkelse (20US).

! – Læs en smule med uret.

. – Læs Data PIN-tilstand (ingen ur).

& – Forsinkelse 1US. Brug 0 & 1 … 255 for flere forsinkelser.

Ved hjælp af det

Her er to eksempler, der viser bussen pirat i aktion. Terminaler skal indstilles til ASCII-tilstand med Local ECHO, vi brugte Windows Serial Terminal. PC-side seriel forbindelse er 115200bps, 8N1. Buspiraten skal reagere på enhver enkelt linje feed type (0x0a, 0x0d) eller begge (Windows Style).

.I2c / spi – flash 24LC1025 EEPROM

Microchip’s EEPROM’er er populære permanente lagringshukommelseschips, 24LC1025 har 128 kbytes opbevaring med en I2C-grænseflade. Vi kan teste denne chip uden bread-boarding en stor kredsløb eller skrive kode.

Billedet viser en 24LC1025 forbundet til buspiratet. EEPROM fungerer fra 2,7 til 5volte, så vi brugte 3.3voltforsyningen fra bussen pirat for at drive kredsløbet. Den indbyggede SDA / SCL-pull-up-modstande holder I2C-bussen højt og eliminerer behovet for eksterne modstande. En enkelt 0,1uf kondensator afkalker EEPROM fra strømforsyningen.

Setup I2C-tilstand

For det første opsætter vi bussen pirat for I2C-tilstand og aktiverer pull-up-modstandene. I betragtning af at Bus Pirate i øjeblikket bruger et software I2C-bibliotek, har hastighedsindstillingen ikke rigtig en effekt.

Spi> m <-ener m til mode Vælg 1. Spi. 2. I2C. 3. UART. 4. RAW 2 Wire 5. RAW 3 Wire Mode> 2 <-Enter 2 til I2C 900 MODE SET. Indstil hastighed: 1. 100kHz (standard) 2. 400kHz (hurtig tilstand) 3. 1MHz (høj hastighed) Hastighed> 1 <-speed gør ikke noget ... 901 hastighedssæt 202 I2C klar, P / P for pullups I2C> P <-Enable I2C pull-up modstande 205 I2C Pullup på I2C>

Skriv til EEPROM (I2C)

Alle I2C-operationer begynder med en startbetingelse {eller [, og enden med en stop tilstand} eller]. En skrivning begynder ved at adressere enheden (1 byte) og forsøge at finde en bekræftelsesbit (ACK). Hvis EEPROM reagerer, kan vi sende data-placeringen til at skrive (2 bytes) og data nyttelast (n bytes). Buspiraten kontrollerer automatisk for en ACK i slutningen af ​​hver skrivning, og ACKS hver læser.

24LC1025-basisadressen er 1010xxy, hvor XX er regnet ud af tilstanden af ​​stifter 2 og 3, og Y er læst (1) eller skriv (0) -tilstand. Vi bundet pins 2 og 3 høje, hvilket gør den fulde skriveadresse 1010110. Vi begynder at skrive til enheden på den første data placering (0 0), og skriv en til tretten ved hjælp af en blanding af dataindgangsformater (1 … 13) .

I2C> {0B10100110 0 0 1 2 3 4 5 6 7 8 9 10 0XB 0XC 13} <-I2C-kommando 210 I2C Start tilstand <-bus start 220 I2C Skriv: 0xa6 fik ACK: Ja <-Address Sendt og ACK modtaget 220 I2C Skriv: 0x00 fik ACK: Ja <-write adresse 220 I2C Skriv: 0x00 fik ACK: Ja <-write adresse 220 I2C Skriv: 0x01 Fik ACK: Ja <-Data ... 220 I2C Skriv: 0x0d Fik ACK: Ja 240 I2C Stop tilstand I2C>

Læs fra EEPROM (I2C)

Læsning af 24LC1025 tager to trin. For det første indstiller en skrivekommando uden data adressekarpernen. For det andet, en læse komm