Photometric Guy
New Member
Hello people,
I’m currently working on a glcd project that has me pulling my hair out for two weeks now. This is what I have going on: I’m building a graphical lcd project that pulls bitmap data from a Atmel 28C64B-15PU eeprom and displays it on the glcd. The project uses a VB6 application I built to upload bitmap data to a PIC16F871 that then writes the data to the eeprom. After the upload the PIC then has the option to pull data and display it on the glcd. I’ve slowly been dismantling the project to find the bug but it’s an elusive one! I’m now to the point of trying to write directly to the eeprom through the PIC’s UART via HyperTerminal then try to read the contents back. All I get is garbage. I’ve played around with different timings and I can get back repeating characters for all address locations after I write to just one address. I can use the glcd in place of the eeprom (with some tweaking) and view the data as it’s downloaded but I just can’t seem to write to the eeprom. The 16F871 is capable of 200uS execution (more like 800uS bus with Picbasic) and the data sheets for the 28C64B spec 150nS as min. and nothing for Max. timing. I’ve tried using decoupling caps., shorten the wire on the breadboard and pulling all unused pins to G. I also tried increasing hold times to offset pin capacitance. I’m almost convinced that it’s a timing problem or a noise/bounce problem. The data sheets are minimal, simplistic, and unclear as to how the latch registers work among other things on the 28C64NB. I’ve googled it and can’t find any articles or ideas on interfacing a 8bit parallel eeprom to a pic. I could use serial memory but then the graphics update is too slow. Anyway I already bought some of these chips. Anyone have any ideas?
I’m currently working on a glcd project that has me pulling my hair out for two weeks now. This is what I have going on: I’m building a graphical lcd project that pulls bitmap data from a Atmel 28C64B-15PU eeprom and displays it on the glcd. The project uses a VB6 application I built to upload bitmap data to a PIC16F871 that then writes the data to the eeprom. After the upload the PIC then has the option to pull data and display it on the glcd. I’ve slowly been dismantling the project to find the bug but it’s an elusive one! I’m now to the point of trying to write directly to the eeprom through the PIC’s UART via HyperTerminal then try to read the contents back. All I get is garbage. I’ve played around with different timings and I can get back repeating characters for all address locations after I write to just one address. I can use the glcd in place of the eeprom (with some tweaking) and view the data as it’s downloaded but I just can’t seem to write to the eeprom. The 16F871 is capable of 200uS execution (more like 800uS bus with Picbasic) and the data sheets for the 28C64B spec 150nS as min. and nothing for Max. timing. I’ve tried using decoupling caps., shorten the wire on the breadboard and pulling all unused pins to G. I also tried increasing hold times to offset pin capacitance. I’m almost convinced that it’s a timing problem or a noise/bounce problem. The data sheets are minimal, simplistic, and unclear as to how the latch registers work among other things on the 28C64NB. I’ve googled it and can’t find any articles or ideas on interfacing a 8bit parallel eeprom to a pic. I could use serial memory but then the graphics update is too slow. Anyway I already bought some of these chips. Anyone have any ideas?