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.
Laitteisto
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
–
B8
CLK
Scl
–
B7
MISO
–
RX
B6
CS
–
TX
B5
Aux
Aux
Aux
Maa
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). Piiri ja PCB luodaan Cadsoft Eaglen freeware-versiolla. 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. Ouch! 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.
Virtalähteet
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).
Osa lista
Osa
Arvo
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
The firmware is written in C using the complimentary demonstration version of the photo C30 compiler. learn all about working with this photo in our introduction to the photo 24F series. 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.
Syntaksi
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 asynchrkuolettavasti.
] tai} – Lopeta data kirjoittaa. SPI / RAW 3 Wire: Siru Valitse Ei käytössä. I2C / RAW 2 Jäähdytys: pysäytystila. RS232: Sulje UART.
R / R – Lue tavu. SPI / RAW 3 Wire: Lähetä Dummy Byte, Return Lue. I2C: Lue tavu ACK: llä. RAW 2 Wire: Lue 8 bittiä. RS232: Tarkista UART tavulle ja palaa tai epäonnistua, jos tyhjä. Käytä 0R1 … 255 irtotavarana lukee jopa 255 tavua.
0B – Kirjoita tämä binaarivarvo. Muoto on 0B00000000 tavulle, mutta osittaiset tavut ovat myös hyvin: 0B1001.
0h tai 0x – Kirjoita tämä HEX-arvo. Muoto on 0h01 tai 0x01. Osittaiset tavut ovat hienoja: 0xa. A-F voi olla pieniä tai isoja kirjaimia.
0-255 – Kirjoita tämä desimaali-arvo. Mikä tahansa numero, jota ei edeltää 0x, 0H tai 0B, tulkitaan desimaaliksi.
tai Space – Arvo Delimeter. Käytä koomia tai tilaa erillisiin numeroihin. Mikä tahansa yhdistelmä on hieno, ei-numeroiden arvojen välillä ei tarvita erotteria: {0xa6,0, 0 16 5 0B111 0HAF}.
Suorat väylän manipulointikomennot RAW 2 -johdon ja RAW 3 -johdotilaan.
^ – Lähetä yksi kello rasti. Käytä 0 ^ 1 … 255 useille kellon punkkeihin.
/ ja \ – Vaihda kellon taso korkea (/) ja matala (\). Sisältää kellon viiveen (100us).
– / _ – Vaihda tietotila korkea (-) ja matala (_). Sisältää Data Setup Delay (20us).
! – Lue yksi bitti kellolla.
. – Lue Data PIN -tila (ei kelloa).
& – Delay 1us. Käytä 0 & 1 … 255 useille viiveille.
Käyttämällä sitä
Tässä on kaksi esimerkkiä, jotka osoittavat väylän merirosvoa toiminnassa. Terminaalit on asetettava ASCII-tilaan paikallisen kaiku, käytimme Windowsin sarjapäätelaitetta. PC-Side-sarjaliitäntä on 115200 bps, 8N1. Linja-laiturin on vastattava mihin tahansa yksittäiseen syöttötyyppiin (0x0A, 0x0d) tai molemmat (Windows Style).
.I2C / SPI – Flash 24LC1025 EEPROM
Microchipin EEPROMS ovat suosittuja pysyviä muistin siruja, 24LC1025: llä on 128 kiloa varastointia I2C-rajapinnassa. Voimme testata tätä sirua ilman leipää suurta piiriä tai kirjoituskoodia.
Kuvassa näkyy 24lC1025 liitetty väylän merirosvoon. EEPROM toimii 2,7: stä 5voltsiin, joten käytimme 3.3voltin syöttöä väylän merirosvosta virtapiiriin. SDA: n SDA / SCL-vetovoima-vastukset pitävät I2C-väylän korkeaa ja poistamaan ulkoisten vastusten tarve. Yksi 0,1UF kondensaattori erottaa EEPROM virtalähteestä.
Aseta I2C-tila
Ensinnäkin asetat bussipaneelin I2C-tilaan ja ota käyttöön vetovastukset. Ottaen huomioon, että bussipirate käyttää tällä hetkellä ohjelmiston I2C-kirjastoa, nopeusasetuksella ei todellakaan ole vaikutusta.
SPI> M <-kenttä M tilassa Valitse 1. SPI 2. i2c 3. UART 4. RAW 2 -johto 5. RAW 3 -johto MODE> 2 <-kenttä 2 I2C: lle 900-tila Aseta nopeus: 1. 100 kHz (standardi) 2. 400 kHz (nopea tila) 3. 1MHz (nopea) Nopeus> 1 <-Speed ei todellakaan tee mitään ... 901 nopeussarja 202 i2c valmis, p / p pullopsille I2c> p
Kirjoita EEPROM (I2C)
Kaikki i2C-toiminnot alkavat aloitusolosuhteella {tai [ja päättyy pysäytystilasta} tai]. Kirjoitus alkaa käsittelemällä laitteeseen (1 tavu) ja yrittää löytää kuittausbitin (ACK). Jos EEPROM reagoi, voimme lähettää datapaikan kirjoittaa (2 tavua) ja datan hyötykuormaa (n bytes). Linja-alue tarkistaa automaattisesti ACK kunkin kirjoitus- ja ACK: n lukemisen jälkeen.
24LC1025-pohjaosoite on 1010xxy, jossa XX tajustaan nastat 2 ja 3, ja Y on luettu (1) tai kirjoittaa (0) tila. Me sidoimme nastat 2 ja 3 korkealla, mikä tekee koko kirjoitusosoitteen 1010110. Aloitamme kirjoittamalla laitteeseen ensimmäisessä datapaikassa (0 0) ja kirjoita yksi tai kolmetoista käyttämällä tietojen syöttömuotoja (1 … 13) .
I2c> {0B10100110 0 0 1 2 3 4 5 6 7 8 9 10 0XB 0xc 13} <-I2C-komento 210 I2C Aloitustila <-Bus alkaa 220 I2C kirjoittaa: 0xa6 sai ACK: Kyllä <-ddress lähetetty ja ACK sai 220 I2C kirjoittaa: 0x00 sai ACK: Kyllä <-Write-osoite 220 I2C kirjoittaa: 0x00 sai ACK: Kyllä <-Write-osoite 220 I2C kirjoittaa: 0x01 sai ACK: Kyllä <-Data ... 220 I2C kirjoittaa: 0x0d sai ACK: Kyllä 240 I2C-pysäytystila I2c>
Lue EEPROM (I2C)
24LC1025: n lukeminen kestää kaksi vaihetta. Ensinnäkin kirjoituskomento, jossa ei ole tietoja, asetetaan osoite osoitin. Toinen, luettu comm