{"id":24312472,"url":"https://github.com/mytechnotalent/atmega328p_ssd1306_driver","last_synced_at":"2026-04-29T13:34:42.869Z","repository":{"id":272529159,"uuid":"916906812","full_name":"mytechnotalent/ATmega328P_SSD1306_Driver","owner":"mytechnotalent","description":"An ATmega328P SSD1306 driver written entirely in Assembler.","archived":false,"fork":false,"pushed_at":"2025-01-15T01:32:37.000Z","size":1272,"stargazers_count":0,"open_issues_count":0,"forks_count":0,"subscribers_count":1,"default_branch":"main","last_synced_at":"2025-01-15T02:56:31.638Z","etag":null,"topics":["arduino","arduino-platform","arduino-programming","assembler","assembly","atmega328p","avr","avr-programming","avrdude","ssd1306"],"latest_commit_sha":null,"homepage":"","language":"Assembly","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"apache-2.0","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/mytechnotalent.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":"LICENSE","code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2025-01-15T01:27:08.000Z","updated_at":"2025-01-15T01:35:39.000Z","dependencies_parsed_at":"2025-01-15T03:10:22.159Z","dependency_job_id":null,"html_url":"https://github.com/mytechnotalent/ATmega328P_SSD1306_Driver","commit_stats":null,"previous_names":["mytechnotalent/atmega328p_ssd1306_driver"],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/mytechnotalent%2FATmega328P_SSD1306_Driver","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/mytechnotalent%2FATmega328P_SSD1306_Driver/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/mytechnotalent%2FATmega328P_SSD1306_Driver/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/mytechnotalent%2FATmega328P_SSD1306_Driver/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/mytechnotalent","download_url":"https://codeload.github.com/mytechnotalent/ATmega328P_SSD1306_Driver/tar.gz/refs/heads/main","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":242667474,"owners_count":20166303,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["arduino","arduino-platform","arduino-programming","assembler","assembly","atmega328p","avr","avr-programming","avrdude","ssd1306"],"created_at":"2025-01-17T08:17:53.224Z","updated_at":"2026-04-29T13:34:42.863Z","avatar_url":"https://github.com/mytechnotalent.png","language":"Assembly","funding_links":[],"categories":[],"sub_categories":[],"readme":"\u003cimg src=\"https://raw.githubusercontent.com/mytechnotalent/ATmega328P_SSD1306_Driver/refs/heads/main/ATmega328P%20SSD1306%20Driver.png\"\u003e\n\n## FREE Reverse Engineering Self-Study Course [HERE](https://github.com/mytechnotalent/Reverse-Engineering-Tutorial)\n\n\u003cbr\u003e\n\n# ATmega328P SSD1306 Driver\nAn ATmega328P SSD1306 driver written entirely in Assembler.\n\n\u003cbr\u003e\n\n# Code\n```assembler\n; ===================================================================\n; Project: ATmega328P SSD1306 Driver\n; ===================================================================\n; Author: Kevin Thomas\n; E-Mail: ket189@pitt.edu\n; Version: 1.0\n; Date: 01/09/25\n; Target Device: ATmega328P (Arduino Nano)\n; Clock Frequency: 16 MHz\n; Toolchain: AVR-AS, AVRDUDE\n; License: Apache License 2.0\n; Description: This program is a simple SSD1306 driver that works\n; with capital letters.\n; ===================================================================\n\n; ===================================================================\n; SYMBOLIC DEFINITIONS\n; ===================================================================\n.equ TWBR, 0xB8 ; TWI Bit Rate Register\n.equ TWSR, 0xB9 ; TWI Status Register\n.equ TWDR, 0xBB ; TWI Data Register\n.equ TWCR, 0xBC ; TWI Control Register\n.equ TWINT, 7 ; TWI Interrupt Flag\n.equ TWEA, 6 ; TWI Enable Acknowledge\n.equ TWSTA, 5 ; TWI Start Condition\n.equ TWSTO, 4 ; TWI Stop Condition\n.equ TWEN, 2 ; TWI Enable Bit\n.equ SSD1306_ADDR, 0x3C ; SSD1306 I2C Address\n\n; ===================================================================\n; PROGRAM ENTRY POINT\n; ===================================================================\n.global program ; global label; make avail external\n.section .text ; start of the .text (code) section\n\n; ===================================================================\n; PROGRAM LOOP\n; ===================================================================\n; Description: Main program loop which executes all subroutines and \n; then repeats indefinitely.\n; -------------------------------------------------------------------\n; Instructions: AVR Instruction Set Manual\n; 6.87 RCALL – Relative Call to Subroutine\n; 6.95 LDI – Load Immediate\n; 6.90 RJMP – Relative Jump\n; ===================================================================\nprogram:\n RCALL TWI_Init ; initialize TWI\n RCALL SSD1306_Init ; initialize SSD1306\n RCALL SSD1306_Clear ; clear the OLED screen\n LDI R16, 0 ; set page to 0\n RCALL Set_Cursor_Page ; move cursor to page 0\n RCALL Display_Eext_KEVIN_T ; display \"KEVIN T\"\n LDI R16, 1 ; set page to 1\n RCALL Set_Cursor_Page ; move cursor to page 1\n RCALL Display_Text_KEVIN_T ; display \"KEVIN T\"\n LDI R16, 2 ; set page to 2\n RCALL Set_Cursor_Page ; move cursor to page 2\n RCALL Display_Text_KEVIN_T ; display \"KEVIN T\"\n LDI R16, 3 ; set page to 3\n RCALL Set_Cursor_Page ; move cursor to page 3\n RCALL Display_Text_KEVIN_T ; display \"KEVIN T\"\n LDI R16, 4 ; set page to 4\n RCALL Set_Cursor_Page ; move cursor to page 4\n RCALL Display_Text_KEVIN_T ; display \"KEVIN T\"\n LDI R16, 5 ; set page to 5\n RCALL Set_Cursor_Page ; move cursor to page 5\n RCALL Display_Text_KEVIN_T ; display \"KEVIN T\"\n LDI R16, 6 ; set page to 6\n RCALL Set_Cursor_Page ; move cursor to page 6\n RCALL Display_Text_KEVIN_T ; display \"KEVIN T\"\n LDI R16, 7 ; set page to 7\n RCALL Set_Cursor_Page ; move cursor to page 7\n RCALL Display_Text_KEVIN_T ; display \"KEVIN T\"\nprogram_loop:\n RJMP program_loop ; infinite loop\n\n; ===================================================================\n; SUBROUTINE: TWI_Init\n; ===================================================================\n; Description: Initializes the Two-Wire Interface (TWI/I2C) module \n; on the ATmega128P for communication at ~100kHz.\n; -------------------------------------------------------------------\n; Instructions: AVR Instruction Set Manual\n; 6.95 LDI – Load Immediate\n; 6.117 STS – Store Direct to Data Space\n; 6.88 RET – Return from Subroutine\n; ===================================================================\nTWI_Init:\n ; -----------------------------------------------------------------\n ; STEP 1: Set TWI Prescaler to 1\n ; -----------------------------------------------------------------\n LDI R16, 0x00 ; load immediate val 0x00 into R16\n ; 0x00 sets TWI Prescaler bits \n ; (TWPS1:0) to 0\n ; prescaler value: 1 (as 4^TWPS)\n STS TWSR, R16 ; store the value in TWI Status\n ; Register (TWSR)\n ; TWSR[1:0] (TWPS1, TWPS0) set the \n ; prescaler\n ; -----------------------------------------------------------------\n ; STEP 2: Set TWI Bit Rate Register for ~100kHz\n ; -----------------------------------------------------------------\n LDI R16, 72 ; load immediate value 72 into R16\n ; this value sets the SCL freq\n ; SCL = F_CPU / \n ; (16 + 2 * TWBR * 4^TWPS)\n ; for F_CPU = 16MHz, TWPS = 1, \n ; TWBR = 72:\n ; SCL ≈ 100kHz\n STS TWBR, R16 ; store the value in TWI Bit Rate \n ; Register (TWBR)\n ; TWBR determines the SCL freq\n ; -----------------------------------------------------------------\n ; STEP 3: Enable TWI Module\n ; -----------------------------------------------------------------\n LDI R16, (1 \u003c\u003c TWEN) ; load immediate value with TWEN \n ; bit set\n ; TWEN (TWI Enable Bit) enables the\n ; TWI hardware\n STS TWCR, R16 ; store the value in TWI Control \n ; Register (TWCR)\n ; TWCR enables TWI operations with\n ; TWEN\n RET ; return from subroutine\n\n; ===================================================================\n; SUBROUTINE: TWI_Write_Byte\n; ===================================================================\n; Description: Sends a start condition, writes the TWI address, \n; control byte, and data byte, then issues a stop \n; condition.\n; -------------------------------------------------------------------\n; Inputs: R22 - Control Byte (0x00: Command, 0x40: Data)\n; R23 - Data Byte\n; -------------------------------------------------------------------\n; Instructions: AVR Instruction Set Manual\n; 6.87 RCALL – Relative Call to Subroutine\n; 6.95 LDI – Load Immediate\n; 6.75 MOV – Copy Register\n; 6.88 RET – Return from Subroutine\n; 6.39 CLR - Clear Register\n; 6.83 ORI – Logical OR with Immediate\n; 6.117 STS – Store Direct to Data Space\n; 6.70 LDS – Load Direct from Data Space\n; 6.101 SBRS – Skip if Bit in Register is Set\n; 6.90 RJMP – Relative Jump\n; ===================================================================\nTWI_Write_Byte:\n RCALL .TWI_Start ; send start condition\n LDI R24, (SSD1306_ADDR \u003c\u003c 1) ; load SSD1306 addr w/ write bit\n RCALL .TWI_Write ; write SSD1306 address\n MOV R24, R22 ; load control byte (Command/Data)\n RCALL .TWI_Write ; write control byte\n MOV R24, R23 ; load data byte\n RCALL .TWI_Write ; write data byte\n RCALL .TWI_Stop ; send stop condition\n RET ; return from subroutine\n.TWI_Start:\n CLR R16 ; clear R16 (initialize to 0)\n ORI R16, (1\u003c\u003cTWINT) ; set TWINT bit to clear int flag\n ORI R16, (1\u003c\u003cTWSTA) ; set TWSTA bit for start cond\n ORI R16, (1\u003c\u003cTWEN) ; set TWEN bit to enable TWI\n STS TWCR, R16 ; write to TWCR to start cond\n.TWI_Wait_Start:\n LDS R17, TWCR ; read TWCR\n SBRS R17, TWINT ; skip if TWINT flag is set\n RJMP .TWI_Wait_Start ; wait for start cond complete\n RET ; return from subroutine\n.TWI_Write:\n STS TWDR, r24 ; Load data into TWDR\n CLR R16 ; clear R16 (initialize to 0)\n ORI R16, (1\u003c\u003cTWINT) ; set TWINT bit clear int flag\n ORI R16, (1\u003c\u003cTWEN) ; set TWEN bit to enable TWI trans\n STS TWCR, R16 ; write to TWCR to start trans\n.TWI_Write_Wait:\n LDS R17, TWCR ; read TWCR\n SBRS R17, TWINT ; skip if TWINT flag is set\n RJMP .TWI_Write_Wait ; wait until write is complete\n RET ; return from subroutine\n.TWI_Stop:\n CLR R16 ; clear R16 (initialize to 0)\n ORI R16, (1\u003c\u003cTWINT) ; set TWINT bit to clear int flag\n ORI R16, (1\u003c\u003cTWSTO) ; set TWSTO bit for stop condition\n ORI R16, (1\u003c\u003cTWEN) ; set TWEN bit to enable TWI\n STS TWCR, R16 ; write to TWCR to init stop cond\n RET ; return from subroutine\n\n; ===================================================================\n; SUBROUTINE: SSD1306_Init\n; ===================================================================\n; Description: Initializes the SSD1306 OLED display by sending a \n; sequence of commands.\n; -------------------------------------------------------------------\n; Instructions: AVR Instruction Set Manual\n; 6.95 LDI – Load Immediate\n; 6.87 RCALL – Relative Call to Subroutine\n; 6.88 RET – Return from Subroutine\n; ===================================================================\nSSD1306_Init:\n ; -----------------------------------------------------------------\n ; STEP 1: Turn Display OFF\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xAE ; cmd: Display OFF\n RCALL TWI_Write_Byte ; send command to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 2: Set Display Clock Divide Ratio/Oscillator Frequency\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xD5 ; cmd: set Disp Clock Divide Ratio\n RCALL TWI_Write_Byte ; send cmd to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x80 ; div Ratio and Oscillator Freq\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 3: Set Multiplex Ratio\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xA8 ; cmd: Set Multiplex Ratio\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x3F ; 1/64 duty for 128x64 display\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 4: Set Display Offset\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xD3 ; cmd: Set Display Offset\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x00 ; value: No offset\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 5: Set Start Line\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x40 ; cmd: Set Start Line at 0\n RCALL TWI_Write_Byte ; send command to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 6: Enable Charge Pump\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x8D ; cmd: Charge Pump Setting\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x14 ; value: Enable charge pump\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 7: Set Memory Addressing Mode\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x20 ; cmd: Set Memory Addressing Mode\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x00 ; value: Horizontal Addressing Mode\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 8: Set Segment Re-map\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xA1 ; cmd: Segment Re-map\n RCALL TWI_Write_Byte ; send command to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 9: Set COM Output Scan Direction\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xC8 ; cmd: COM Output Scan Direction\n RCALL TWI_Write_Byte ; send command to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 10: Set COM Pins Hardware Configuration\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xDA ; cmd: Set COM Pins Hardware Config\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x12 ; value: alt COM pin config\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 11: Set Contrast Control\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x81 ; cmd: Set Contrast Control\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xCF ; value: Set contrast\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 12: Set Pre-Charge Period\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xD9 ; cmd: Set Pre-charge Period\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xF1 ; value: P1 = 15 DCLKs, P2 = 1 DCLK\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 13: Set VCOMH Deselect Level\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xDB ; cmd: Set VCOMH Deselect Level\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0x40 ; Value: 0.77 x Vcc\n RCALL TWI_Write_Byte ; send value to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 14: Set Entire Display On/Resume\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xA4 ; cmd: Resume to RAM Content Disp\n RCALL TWI_Write_Byte ; send command to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 15: Set Normal Display\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xA6 ; cmd: Normal Display\n RCALL TWI_Write_Byte ; send command to SSD1306\n ; -----------------------------------------------------------------\n ; STEP 16: Turn Display On\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; load Control Byte (Command Mode)\n LDI R23, 0xAF ; cmd: Display ON\n RCALL TWI_Write_Byte ; send command to SSD1306\n RET ; return from subroutine\n\n; ===================================================================\n; SUBROUTINE: SSD1306_Clear\n; ===================================================================\n; Description: Clears the OLED screen and resets the cursor to the \n; top-left.\n; -------------------------------------------------------------------\n; Instructions: AVR Instruction Set Manual\n; 6.95 LDI – Load Immediate\n; 6.86 PUSH – Push Register on Stack\n; 6.87 RCALL – Relative Call to Subroutine\n; 6.49 DEC – Decrement\n; 6.23 BRNE – Branch if Not Equal\n; 6.85 POP – Pop Register from Stack\n; 6.88 RET – Return from Subroutine\n; ===================================================================\nSSD1306_Clear:\n ; -----------------------------------------------------------------\n ; STEP 1: Clear OLED Screen\n ; -----------------------------------------------------------------\n LDI R22, 0x40 ; Control Byte: Data Mode\n LDI R23, 0x00 ; Data Byte: 0x00 (Clear)\n LDI R24, 8 ; 8 pages (for 128x64 display)\n.Clear_Loop:\n PUSH R24 ; save page counter\n LDI R25, 128 ; 128 columns per page\n.Clear_Page:\n RCALL TWI_Write_Byte ; write 0x00 to clear pixel\n DEC R25 ; decrement column counter\n BRNE .Clear_Page ; repeat until all cols cleared\n POP R24 ; restore page counter\n DEC R24 ; decrement page counter\n BRNE .Clear_Loop ; repeat for all 8 pages\n ; -----------------------------------------------------------------\n ; STEP 2: Reset Cursor to Top-Left (0,0)\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; Control Byte: Command Mode\n LDI R23, 0x21 ; cmd: Set Column Address\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R23, 0x00 ; Column Start Address (0)\n RCALL TWI_Write_Byte ; send start address\n LDI R23, 0x7F ; Column End Address (127)\n RCALL TWI_Write_Byte ; send end address\n LDI R22, 0x00 ; Control Byte: Command Mode\n LDI R23, 0x22 ; cmd: Set Page Address\n RCALL TWI_Write_Byte ; send command to SSD1306\n LDI R23, 0x00 ; Page Start Address (0)\n RCALL TWI_Write_Byte ; send start address\n LDI R23, 0x07 ; Page End Address (7)\n RCALL TWI_Write_Byte ; send end address\n RET ; return from subroutine\n\n; ===================================================================\n; SUBROUTINE: Set_Cursor_Page\n; ===================================================================\n; Description: Sets the cursor to a specific page (row) on the OLED\n; display.\n; -------------------------------------------------------------------\n; Inputs: R16 - Page Number (0 to 7 for 128x64 display)\n; -------------------------------------------------------------------\n; Instructions: AVR Instruction Set Manual\n; 6.86 PUSH – Push Register on Stack\n; 6.95 LDI – Load Immediate\n; 6.87 RCALL – Relative Call to Subroutine\n; 6.85 POP – Pop Register from Stack\n; 6.75 MOV – Copy Register\n; 6.88 RET – Return from Subroutine\n; ===================================================================\nSet_Cursor_Page:\n ; -----------------------------------------------------------------\n ; STEP 1: Set Column Address to Start at 0\n ; -----------------------------------------------------------------\n PUSH R16 ; save R16 to the stack\n LDI R22, 0x00 ; Control Byte: Command Mode\n LDI R3, 0x21 ; cmd: Set Column Address\n RCALL TWI_Write_Byte ; send command\n LDI R23, 0x00 ; Column Start Address: 0\n RCALL TWI_Write_Byte ; send start address\n LDI R23, 0x7F ; Column End Address: 127\n RCALL TWI_Write_Byte ; send end address\n ; -----------------------------------------------------------------\n ; STEP 2: Set Page Address\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; Control Byte: Command Mode\n LDI R23, 0x22 ; cmd: Set Page Address\n RCALL TWI_Write_Byte ; send command\n POP R16 ; restore R16 from the stack\n MOV R23, R16 ; copy page number from R16 to R23\n RCALL TWI_Write_Byte ; send page start address\n ; -----------------------------------------------------------------\n ; STEP 3: Reset Cursor to Leftmost Column (Column Address 0)\n ; -----------------------------------------------------------------\n LDI R22, 0x00 ; Control Byte: Command Mode\n LDI R23, 0x00 ; cmd: Set Column Address Start\n RCALL TWI_Write_Byte ; send column start address\n RET ; return from subroutine\n\n; ===================================================================\n; SUBROUTINE: Display_Char\n; ===================================================================\n; Description: Displays a single character on the OLED screen.\n; -------------------------------------------------------------------\n; Inputs: R16 - ASCII code of the letter to display\n; -------------------------------------------------------------------\n; Instructions: AVR Instruction Set Manual\n; 6.95 LDI – Load Immediate\n; 6.47 CPI – Compare with Immediate\n; 6.14 BREQ – Branch if Equal\n; 6.20 BRLO – Branch if Lower (Unsigned)\n; 6.11 BRCC – Branch if Carry Cleared\n; 6.120 SUBI – Subtract Immediate\n; 6.87 RCALL – Relative Call to Subroutine\n; 6.75 MOV – Copy Register\n; 6.73 LSL – Logical Shift Left\n; 6.2 ADD – Add without Carry\n; 6.1 ADC – Add with Carry\n; 6.72 LPM – Load Program Memory\n; 6.88 RET – Return from Subroutine\n; ===================================================================\nDisplay_Char:\n ; -----------------------------------------------------------------\n ; STEP 1: Check Character Validity\n ; -----------------------------------------------------------------\n LDI R22, 0x40 ; Control Byte: Data Mode\n CPI R16, 0x20 ; check if char is SPACE (0x20)\n BREQ .Is_Space ; branch if equal to .Is_Space \n CPI R16, 'A' ; check if char is 'A' or higher\n BRLO .Invalid_Char ; if less than 'A', invalid\n CPI R16, 'Z' ; check if char is 'Z' or lower\n BRCC .Invalid_Char ; if greater than 'Z', invalid\n SUBI R16, 'A' ; .calculate index: R16 - 'A'\n RJMP .Calculate_Index ; jump to .Calculate_Index\n.Is_Space:\n LDI R16, 26 ; index for space in Font_Table\n RJMP .Calculate_Index ; jump to .Calculate_Index\n.Invalid_Char:\n LDI R16, 26 ; SPACE as default invalid chars\n.Calculate_Index:\n ; -----------------------------------------------------------------\n ; STEP 2: Calculate Font Data Address\n ; -----------------------------------------------------------------\n LDI R30, LO8(font_table) ; load lower byte into base addr\n LDI R31, HI8(font_table) ; load higher byte into base addr\n MOV R17, R16 ; copy index to R17\n LSL R17 ; R17 = index * 2\n ADD R17, R16 ; R17 = index * 3\n LSL R17 ; R17 = index * 6\n ADD R17, R16 ; R17 = index * 7\n ADD R30, R17 ; add offset Z-pointer (low byte)\n ADC R31, R1 ; add carry Z-pointer (high byte)\n ; -----------------------------------------------------------------\n ; STEP 3: Display Character\n ; -----------------------------------------------------------------\n LPM R23, Z+ ; load font byte 1\n RCALL TWI_Write_Byte ; write font byte 1\n LPM R23, Z+ ; load font byte 2\n RCALL TWI_Write_Byte ; write font byte 2\n LPM R23, Z+ ; load font byte 3\n RCALL TWI_Write_Byte ; write font byte 3\n LPM R23, Z+ ; load font byte 4\n RCALL TWI_Write_Byte ; write font byte 4\n LPM R23, Z+ ; load font byte 5\n RCALL TWI_Write_Byte ; write font byte 5\n LPM R23, Z+ ; load font byte 6\n RCALL TWI_Write_Byte ; write font byte 6\n LPM R23, Z+ ; load font byte 7\n RCALL TWI_Write_Byte ; write font byte 7\n RET ; return from subroutine\n\n; ===================================================================\n; SUBROUTINE: Display_Text_KEVIN_T\n; ===================================================================\n; Description: Displays the text \"KEVIN T\" on the current cursor \n; position of the OLED display.\n; -------------------------------------------------------------------\n; Instructions: AVR Instruction Set Manual\n; 6.95 LDI – Load Immediate\n; 6.87 RCALL – Relative Call to Subroutine\n; 6.88 RET – Return from Subroutine\n; ===================================================================\nDisplay_Text_KEVIN_T:\n ; Display \"KEVIN T\"\n LDI R16, 'K' ; load ASCII value of 'K' into R16\n RCALL Display_Char ; display 'K'\n LDI R16, 'E' ; load ASCII value of 'E' into R16\n RCALL Display_Char ; display 'E'\n LDI R16, 'V' ; load ASCII value of 'V' into R16\n RCALL Display_Char ; display 'V'\n LDI R16, 'I' ; load ASCII value of 'I' into R16\n RCALL Display_Char ; display 'I'\n LDI R16, 'N' ; load ASCII value of 'N' into R16\n RCALL Display_Char ; display 'N'\n LDI R16, ' ' ; load ASCII value of space R16\n RCALL Display_Char ; display space\n LDI R16, 'T' ; load ASCII value of 'T' into R16\n RCALL Display_Char ; display 'T'\n RET ; return from subroutine\n\n; ===================================================================\n; FONT TABLE: A-Z AND SPACE\n; ===================================================================\n; Description: Defines the font data for characters A-Z and space as \n; each character consists of 7 bytes.\n; ===================================================================\nFont_Table:\n ; LETTER_A\n .byte 0x00, 0x7C, 0x12, 0x11, 0x12, 0x7C, 0x00\n ; LETTER_B\n .byte 0x00, 0x7F, 0x49, 0x49, 0x49, 0x36, 0x00\n ; LETTER_C\n .byte 0x00, 0x3E, 0x41, 0x41, 0x41, 0x22, 0x00\n ; LETTER_D\n .byte 0x00, 0x7F, 0x41, 0x41, 0x22, 0x1C, 0x00 \n ; LETTER_E\n .byte 0x00, 0x7F, 0x49, 0x49, 0x49, 0x41, 0x00\n ; LETTER_F\n .byte 0x00, 0x7F, 0x09, 0x09, 0x09, 0x01, 0x00\n ; LETTER_G\n .byte 0x00, 0x3E, 0x41, 0x49, 0x49, 0x7A, 0x00\n ; LETTER_H\n .byte 0x00, 0x7F, 0x08, 0x08, 0x08, 0x7F, 0x00\n ; LETTER_I\n .byte 0x00, 0x00, 0x41, 0x7F, 0x41, 0x00, 0x00\n ; LETTER_J\n .byte 0x00, 0x20, 0x40, 0x41, 0x3F, 0x01, 0x00\n ; LETTER_K\n .byte 0x00, 0x7F, 0x08, 0x14, 0x22, 0x41, 0x00\n ; LETTER_L\n .byte 0x00, 0x7F, 0x40, 0x40, 0x40, 0x40, 0x00\n ; LETTER_M\n .byte 0x00, 0x7F, 0x02, 0x0C, 0x02, 0x7F, 0x00\n ; LETTER_N\n .byte 0x00, 0x7F, 0x04, 0x08, 0x10, 0x7F, 0x00\n ; LETTER_O\n .byte 0x00, 0x3E, 0x41, 0x41, 0x41, 0x3E, 0x00\n ; LETTER_P\n .byte 0x00, 0x7F, 0x09, 0x09, 0x09, 0x06, 0x00\n ; LETTER_Q\n .byte 0x00, 0x3E, 0x41, 0x51, 0x21, 0x5E, 0x00\n ; LETTER_R\n .byte 0x00, 0x7F, 0x09, 0x19, 0x29, 0x46, 0x00\n ; LETTER_S\n .byte 0x00, 0x46, 0x49, 0x49, 0x49, 0x31, 0x00\n ; LETTER_T\n .byte 0x00, 0x01, 0x01, 0x7F, 0x01, 0x01, 0x00\n ; LETTER_U\n .byte 0x00, 0x3F, 0x40, 0x40, 0x40, 0x3F, 0x00\n ; LETTER_V\n .byte 0x00, 0x1F, 0x20, 0x40, 0x20, 0x1F, 0x00\n ; LETTER_W\n .byte 0x00, 0x3F, 0x40, 0x38, 0x40, 0x3F, 0x00\n ; LETTER_X\n .byte 0x00, 0x63, 0x14, 0x08, 0x14, 0x63, 0x00\n ; LETTER_Y\n .byte 0x00, 0x07, 0x08, 0x70, 0x08, 0x07, 0x00\n ; LETTER_Z\n .byte 0x00, 0x61, 0x51, 0x49, 0x45, 0x43, 0x00\n ; SPACE\n .byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00\n```\n\n\u003cbr\u003e\n\n# License\n[Apache License 2.0](https://github.com/mytechnotalent/ATmega328P_SSD1306_Driver/blob/main/LICENSE)\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fmytechnotalent%2Fatmega328p_ssd1306_driver","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fmytechnotalent%2Fatmega328p_ssd1306_driver","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fmytechnotalent%2Fatmega328p_ssd1306_driver/lists"}