dcooperdalrymple / picoprom

Raspberry Pi Pico DIP-EEPROM Programmer

PicoPROM - DIP-EEPROM Programmer based on Raspberry Pi Pico

Writes ROM images to parallel-interface EEPROMs via XMODEM file transfer over USB.

Pico connected to EEPROM		Demo video on YouTube

Warning

The Raspberry Pi Pico is not 5V-tolerant, but these EEPROMs are 5V devices. This is fine for write-only access, but it's important to ensure the EEPROM never writes back to the Pico's GPIO pins. Make sure OE is permanently wired high, to VCC, to prevent this.

Features

• No additional components are required - just the Pico and the EEPROM
• XMODEM+CRC transfer protocol makes it easy to send files to be written to the EEPROM
• Fast operation - comparable to TL866
• Supports paged writes as well as byte-writes
• Supports write protection

Not features

• Reading back and verifying is not supported and probably won't ever be
• YMODEM, ZMODEM, and other XMODEM extensions aren't supported yet

Binary Installation

1. Without an EEPROM connected, hold BOOTSEL and connect the Raspberry Pi Pico
2. Drag picoprom.uf2 into the Raspberry Pi Pico's mass storage window
3. It should then reboot and start communicating over USB Serial

Usage

1. Disconnect the Raspberry Pi Pico from power/USB
2. Wire the Raspberry Pi Pico up to the EEPROM according to the pinout table below
3. Connect the Raspberry Pi Pico to the computer by USB
4. Launch a terminal app with XMODEM support, such as Tera Term, and connect it to the Raspberry Pi Pico
5. Verify that the Raspberry Pi Pico is reporting that it's ready to receive a ROM image
6. Use your terminal to send a ROM image using the XMODEM+CRC protocol
7. Disconnect power before removing the EEPROM from the circuit

Alternatively, instead of starting the XMODEM transfer, press Enter for some configuration options and follow the instructions.

Pinout

The pinout is quite straightforward - the pins are laid out around the Pico in almost the same arrangement that they appear on the EEPROM, to make it easy and tidy to wire up.

Make sure OE is connected high, to VCC, as allowing it to float low could cause damage to your Pico.

Pico pin	EEPROM pin	Function		Pico pin	EEPROM pin	Function
GP3	1	A14		VSYS	28	VCC
GP4	2	A12		GND	27	WE
GP5	3	A7		GP2	26	A13
GP6	4	A6		GP28	25	A8
GP7	5	A5		GP27	24	A9
GP8	6	A4		GP26	23	A11
GP9	7	A3		VSYS	22	OE
GP10	8	A2		GP22	21	A10
GP11	9	A1		GP21	20	CE
GP12	10	A0		GP20	19	D7
GP13	11	D0		GP19	18	D6
GP14	12	D1		GP18	17	D5
GP15	13	D2		GP17	16	D4
GND	14	GND		GP16	15	D3

Other options

Depending upon preference, you could swap the CE and WE connections, or connect them both to GP21. It doesn't make any difference to the programming operation, I just chose this layout because it seemed most convenient to me.

If you go further and change the GP pin numbering then you'll need to update the corresponding array in picoprom.c.

Cloning and Building from Source

1. Set up pico-sdk according to the Pico's getting-started guide.
2. Clone this repository alongside pico-sdk
3. Create a build folder
4. From within the build folder, type: cmake ..
5. From within the build folder, type: make

ROM Verification Support

In order to verify EEPROM contents after writing, an octal bus transceiver such as the 74HC245 must be used on the data bus between the Pico and the EEPROM. The output enable and write enable pins must also be connected to GP0 and GP1 respectively. The direction of this transceiver is controlled by the OE pin. Please refer to the included schematic for appropriate wiring.