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If you've got one of Hack a Day's Bus Pirates, what do you do with it? Learn about 1-wire, I2C, and SPI EEPROMs with the 3EEPROM explorer board (we call it the THR-EE-PROM).
EEPROM is a type of memory chip that stores data without a continuous power supply. It's useful for permanent data storage in small logger circuits, or holding custom pages in a mini web server. EEPROMs come in lots of sizes and protocols.
The 3EEPROM has three common EEPROM chips: the DS2431 (1-Wire), 24AA- (I2C), and 25AA- (SPI). All three were previously demonstrated on Hack a Day, but each demo uses a different version of the Bus Pirate hardware and firmware, its difficult for a beginner to follow using a Bus Pirate v2go.
Continue reading for an updated, step by step guide to using the DS2431, 24AA-, and 25AA- EEPROMs with the Bus Pirate v2go. We've also got the full session logs as text files so you won't miss a single detail.
We can have 3EEPROM explorer board PCBs or kits produced at Seeed Studio. PCBs are about $10, kits are about $15, shipped worldwide. We need to organize a group purchase of 10 PCBs or 20 kits to get started. If you're interested in a Bus Pirate, version 3 is coming.
I couldn't include some formatting elements and HTML tables in an Instructable, you can see the original post at the Dangerous Prototypes blog.
EEPROM is a type of memory chip that stores data without a continuous power supply. It's useful for permanent data storage in small logger circuits, or holding custom pages in a mini web server. EEPROMs come in lots of sizes and protocols.
The 3EEPROM has three common EEPROM chips: the DS2431 (1-Wire), 24AA- (I2C), and 25AA- (SPI). All three were previously demonstrated on Hack a Day, but each demo uses a different version of the Bus Pirate hardware and firmware, its difficult for a beginner to follow using a Bus Pirate v2go.
Continue reading for an updated, step by step guide to using the DS2431, 24AA-, and 25AA- EEPROMs with the Bus Pirate v2go. We've also got the full session logs as text files so you won't miss a single detail.
We can have 3EEPROM explorer board PCBs or kits produced at Seeed Studio. PCBs are about $10, kits are about $15, shipped worldwide. We need to organize a group purchase of 10 PCBs or 20 kits to get started. If you're interested in a Bus Pirate, version 3 is coming.
I couldn't include some formatting elements and HTML tables in an Instructable, you can see the original post at the Dangerous Prototypes blog.
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Signing UpStep 13EEPROM hardware overview
The goal of this prototype is to learn about EEPROM and three common bus protocols. First, we look at the 3EEPROM PCB, then we demonstrate each EEPROM using a Bus Pirate universal serial interface tool. If you don't have a Bus Pirate, you can still follow along because the basic order of interface operations remains the same no matter how you implement them.
Circuit
Full size schematic [PNG]. We made the circuit and PCB using the freeware version of Cadsoft Eagle. You can download the schematic and PCB from the Bus Pirate SVN archive.
The 3EEPROM PCB holds a DS2431 1-Wire EEPROM (IC1), a 24AA- I2C EEPROM (IC4), and a 25AA- SPI EEPROM (IC5).
The DS2431 (IC1) draws power parasitically from the 1-Wire bus, it doesn't have an external power supply pin and doesn't require a decoupling capacitor. IC2 and IC3 are empty spots for additional 1-Wire devices, like another DS2431 or a DS1822 temperature sensor. C1 (0.01uF) is optional and only needed if IC2 or IC3 are populated with a powered 1-Wire device.
1-Wire requires a strong pull-up resistor, a maximum of 2.2K ohms. The Bus Pirate's on-board pull-up resistors are 10K, too weak to properly power the DS2431 during writes. The 3EEPROM explorer board includes a 1.8k ohm, 1/8th watt pull-up resistor (R1) on the 1-Wire bus so that no additional pull-up resistor is needed.
The 24AA-(IC4) and 25AA- (IC5) each get a 0.1uF capacitor to decouple them from the power supply (C2, C3). You probably don't need the capacitors in such a simple circuit, we omitted them from the prototype board in the demonstration. The I2C bus used by the 24AA- also requires pull-up resistors, but the Bus Pirate's on-board 10K ohm pull-up resistors are sufficient.
All the components will operate from 2.8volts to 5volts DC. The circuit is powered through the VCC and GND pins of jumper 3. There's two VCC pins, one is for power, the other is for the Bus Pirate's pull-up resistor voltage input pin (Vpullup).
PCB
We made the circuit and PCB using the freeware version of Cadsoft Eagle. You can download the schematic and PCB from the Bus Pirate SVN archive. If you'd like a professionally prepared PCB or 3EEPROM kit, we might be able to arrange a group purchase if 10 or 20 people are interested.
Parts list
R1 1800 ohm resistor (1/8th watt)
C2,3 0.1uF capacitor/10volts+
JP1-4 0.1" male pin header
IC1 DS2431 1K 1-wire EEPROM TO-92
IC4** 24AA014-I/P I2C EEPROM DIP8
IC5** 25AA010A-I/P SPI EEPROM DIP8
ICS4,5 8 pin DIP socket for IC5, 6
**IC4, IC5 could be any size, we linked to small chips, we used 128bytes and 128Kbytes.
I couldn't include some formatting and HTML tables in an Instructable, you can see the original post at the Dangerous Prototypes blog.
Circuit
Full size schematic [PNG]. We made the circuit and PCB using the freeware version of Cadsoft Eagle. You can download the schematic and PCB from the Bus Pirate SVN archive.
The 3EEPROM PCB holds a DS2431 1-Wire EEPROM (IC1), a 24AA- I2C EEPROM (IC4), and a 25AA- SPI EEPROM (IC5).
The DS2431 (IC1) draws power parasitically from the 1-Wire bus, it doesn't have an external power supply pin and doesn't require a decoupling capacitor. IC2 and IC3 are empty spots for additional 1-Wire devices, like another DS2431 or a DS1822 temperature sensor. C1 (0.01uF) is optional and only needed if IC2 or IC3 are populated with a powered 1-Wire device.
1-Wire requires a strong pull-up resistor, a maximum of 2.2K ohms. The Bus Pirate's on-board pull-up resistors are 10K, too weak to properly power the DS2431 during writes. The 3EEPROM explorer board includes a 1.8k ohm, 1/8th watt pull-up resistor (R1) on the 1-Wire bus so that no additional pull-up resistor is needed.
The 24AA-(IC4) and 25AA- (IC5) each get a 0.1uF capacitor to decouple them from the power supply (C2, C3). You probably don't need the capacitors in such a simple circuit, we omitted them from the prototype board in the demonstration. The I2C bus used by the 24AA- also requires pull-up resistors, but the Bus Pirate's on-board 10K ohm pull-up resistors are sufficient.
All the components will operate from 2.8volts to 5volts DC. The circuit is powered through the VCC and GND pins of jumper 3. There's two VCC pins, one is for power, the other is for the Bus Pirate's pull-up resistor voltage input pin (Vpullup).
PCB
We made the circuit and PCB using the freeware version of Cadsoft Eagle. You can download the schematic and PCB from the Bus Pirate SVN archive. If you'd like a professionally prepared PCB or 3EEPROM kit, we might be able to arrange a group purchase if 10 or 20 people are interested.
Parts list
R1 1800 ohm resistor (1/8th watt)
C2,3 0.1uF capacitor/10volts+
JP1-4 0.1" male pin header
IC1 DS2431 1K 1-wire EEPROM TO-92
IC4** 24AA014-I/P I2C EEPROM DIP8
IC5** 25AA010A-I/P SPI EEPROM DIP8
ICS4,5 8 pin DIP socket for IC5, 6
**IC4, IC5 could be any size, we linked to small chips, we used 128bytes and 128Kbytes.
I couldn't include some formatting and HTML tables in an Instructable, you can see the original post at the Dangerous Prototypes blog.
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